Assessment of Comorbid Obsessive-Compulsive Disorder and Posttraumatic Stress Disorder

Abstract

Obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD) are commonly comorbid and share prominent features (e.g., intrusions, safety behaviors, and avoidance). Excellent self-report and clinician-administered assessments exist for OCD and PTSD individually, but few assess both disorders, and even fewer provide instruction on differential diagnosis or detection of comorbid OCD and PTSD. To address this gap in the literature, the current paper aims to (1) highlight diagnostic and functional similarities and differences between OCD and PTSD to inform differential diagnosis, (2) outline assessment recommendations for individuals with suspected comorbid OCD and PTSD, OCD with a significant trauma history or posttraumatic symptoms, or PTSD with significant obsessive-compulsive symptoms, and (3) explore future directions to evaluate and improve methods for assessing co-occurring OCD and PTSD.

Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is characterized by intrusive and unwanted thoughts, urges, and imagery that provokes emotional distress (obsessions) and/or repetitive, ritualistic mental or behavioral acts (compulsions) typically performed to reduce distress and obsessions (American Psychiatric Association [APA], 2022). Common obsessions include fears of contamination, causing harm to others, and feelings of incompleteness (APA, 2022). Common compulsions include washing/cleaning, checking, counting, or repeating words silently (APA, 2022). Although OCD has a relatively low prevalence (≈ 2.3% lifetime prevalence in the general population; Kessler et al., 2005; Ruscio et al., 2010), subclinical obsessive-compulsive (OC) symptoms are common (e.g., ≈ 21% to 25% of the general population; Fullana et al., 2009).

Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) is a psychiatric disorder that develops following exposure to a traumatic event or events (APA, 2022). A “Criterion A” traumatic event (APA, 2022) involves actual or threatened death, serious injury, or sexual violence that an individual directly experiences or witnesses, learns about happening to a close friend or relative, or experiences through repeated or extreme exposure to details. In addition to trauma exposure, the presence of symptoms within each of the following four clusters is needed for a PTSD diagnosis: (Criterion B, ≥ 1 symptom needed)—trauma-related intrusions (e.g., intense memories, flashbacks, nightmares); (Criterion C, ≥ 1 symptom needed)—avoidance of trauma-associated stimuli; (Criterion D, ≥ 2 symptoms needed)—negative changes in mood and cognition (e.g., persistent negative emotions or beliefs about the self or world); and (Criterion E, ≥ 2 symptoms needed)—changes in arousal and reactivity (e.g., hypervigilance, sleep disturbance; APA, 2022).

About 90% of the population will experience at least one Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; APA, 2013) Criterion A event in their lifetime (Kilpatrick et al., 2013) and subsequent posttraumatic stress symptoms are common immediately following trauma exposure (Bryant et al., 2011; Frommberger et al., 1998; Isserlin et al., 2008; Rothbaum et al., 1992; Sloan, 1988). However, PTSD symptoms resolve on their own for approximately two-thirds of trauma-exposed individuals (Blanchard et al., 1997; Rothbaum et al., 1992; Sloan, 1988). As such, the lifetime prevalence of PTSD is only a 8.3% (Kilpatrick et al., 2013).

Comorbidity Between OCD and PTSD

Among individuals with OCD, lifetime prevalence of PTSD is high (e.g., 19%; Fontenelle et al., 2012), and among individuals with PTSD, lifetime prevalence of OCD is high (e.g., 41%; Nacasch et al., 2011). In a national sample of individuals with OCD and lifetime PTSD, 20.7% experienced OCD and PTSD onset within the same year, 39.9% experienced OCD onset following PTSD, and 39.4% experienced OCD onset prior to PTSD (Ruscio et al., 2010). Those who developed OCD after PTSD reported later age of OCD onset (M age = 24.5, SD = 11.7) and earlier age of trauma exposure (M age = 14.7, SD = 9.8) than those who developed OCD before PTSD (M age onset = 15.2, SD = 7.3; M age trauma exposure = 27.2, SD = 11.5; Fontenelle et al., 2012). Individuals with co-occurring OCD and PTSD report more severe OCD symptoms compared to individuals with OCD alone, but comorbid OCD does not appear to significantly affect PTSD symptom severity (Pinciotti & Orcutt, 2020; Pinciotti, Wetterneck, et al., 2022). Individuals with OCD and PTSD also report poorer insight into obsessions and impaired quality of life (Ojserkis et al., 2017) and may experience diminished treatment response (Pinciotti et al., 2020) compared to individuals with OCD or PTSD alone.

Importantly, much of the research regarding prevalence rates and symptom overlap in OCD and PTSD was conducted before 2013 using Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; APA, 1994) criteria, which is a notable limitation. The inclusion of this older research in the current manuscript is justified due to the limited changes between DSM-IV and DSM-5 criteria for OCD and research that has demonstrated similar rates of PTSD diagnosis using Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR; APA, 2000) and DSM-5 criteria (Kilpatrick et al., 2013). No changes were made to the diagnostic criteria for OCD or PTSD in adults in the Diagnostic and Statistical Manual of Mental Disorders (5th ed., text rev.; DSM-5-TR; APA, 2022). Nonetheless, further research on prevalence rates and overlapping symptoms among individuals with DSM-5-defined OCD and PTSD is needed.

Connectivity Between OCD and PTSD: Issues to Consider in Assessment

High rates of comorbidity and worse symptom expression among those with comorbid OCD and PTSD can be partially explained by significant symptom overlap (Fletcher et al., 2020; Pinciotti, Horvath, et al., 2022). Both clinicians and patients can have difficulty distinguishing between OCD and PTSD symptoms (Franklin & Raines, 2019; Huppert et al., 2005), making differential diagnosis challenging. In the following section, we highlight diagnostic and functional similarities and differences between OCD and PTSD to inform differential diagnosis.

Stress and Trauma

Like PTSD, early life stress and premorbid trauma exposure increases the risk and severity of OCD (Adams et al., 2018; Agorastos et al., 2019; An et al., 2019; Brander et al., 2016; Carpenter & Chung, 2011; Cromer et al., 2007; Fontenelle et al., 2012; Gershuny et al., 2008). Further, trauma exposure seems to worsen OCD symptoms among those who had OCD before the traumatic experience (Fontenelle et al., 2011; Rosso et al., 2012). As such, the presence of Criterion A trauma(s) will not distinguish between OCD and PTSD. However, the absence of such an event would preclude a PTSD diagnosis. In both OCD and PTSD, patients will often report that they are fearful that something traumatic will happen. In PTSD, this fear must result, in part, from past traumatic experience(s). Thus, an individual reporting only feared future events (e.g., their house burning down) but no previous Criterion A trauma should be assessed for OCD or an anxiety disorder, while PTSD can be ruled out.

Intrusions

Intrusions are ubiquitous in the general population (Rachman & de Silva, 1978). Recurrent intrusions, namely, obsessions and posttraumatic intrusions (or re-experiencing), are primary to the diagnosis of OCD and PTSD, respectively. At their core, obsessions and re-experiencing are quite similar, though important differences exist. In addition to thoughts or images, obsessions in OCD can also include urges or impulses, whereas re-experiencing in PTSD can also include nightmares, flashbacks, and emotional or physical distress when exposed to traumatic reminders (APA, 2022). To meet the criteria for an obsession, “the individual attempts to ignore or suppress such thoughts, urges, or images, or to neutralize them with some other thought or action” (APA, 2022). No such suppression criteria are explicitly outlined in the definition of re-experiencing, but avoidance or suppression of intrusions is implied in Criterion C (persistent avoidance) and, to a lesser degree, Criterion E (e.g., hypervigilance and externalizing behaviors). Intrusions are commonly avoided or suppressed in both disorders (Pinciotti, Horvath, et al., 2022).

In PTSD, intrusions are only related to the patient’s traumatic experience(s) (APA, 2022). However, there are phenomena observed in PTSD that closely resemble common obsessions. For example, some PTSD patients report chronic doubts about whether an environment is secure that are virtually identical to responsibility/threat obsessions (e.g., worries about whether doors are locked). To be clear, such hypervigilance and associated doubts are not necessarily re-experiencing symptoms, though re-experiencing can accompany such symptoms (e.g., recalling a past break-in and assault).

Though not the norm, it is possible for OCD patients to experience obsessions that relate to traumatic events and appear like re-experiencing symptoms. For example, Pinciotti (2023) describes the case of TB, who experiences detailed, intrusive memories about their father’s unexpected death. Although this symptom initially appears to be posttraumatic re-experiencing, further assessment uncovers that TB finds these intrusions distressing, not because of the content itself, but because of the belief that thinking about the traumatic event will increase the likelihood of a similar event happening to another loved one. The distress derived from believing that TB’s thoughts will cause future harm confirms that this is a trauma-related obsession, as opposed to posttraumatic re-experiencing. Aspects of past trauma (e.g., significant colors, words, or smells) can also be integrated into obsessions (Maloney et al., 2019; Veale et al., 2015). For example, Gershuny and colleagues (2003) presented a client who feared the number 54 and felt contaminated following exposure to the number. Further assessment revealed that the client’s mother was 54 years old when she was murdered, indicating that a traumatic reminder had likely generalized into an obsessional subtype (Gershuny et al., 2003).

In the case of OCD, feelings of mental contamination (i.e., feeling dirty in the absence of contact with a contaminant) are usually characterized as contamination obsessions (Rachman, 2006). Following sexual victimization, some individuals may also report recurrent and intrusive feelings of mental contamination and associated unwanted thoughts (e.g., “because of the assault I am tainted”; Badour et al., 2012). Moreover, these feelings of trauma-related mental contamination can be triggered by reminders of the assault and are associated with severity of posttraumatic stress symptoms (Adams et al., 2014; Badour et al., 2013). However, it is not yet clear if or how feelings of mental contamination fit within the diagnostic criteria of PTSD.

Obsessions and re-experiencing symptoms can often be distinguished by examining the temporal focus of the intrusions (Pinciotti, Fontenelle, et al., 2022). Re-experiencing intrusions are, by definition, past-focused, even if they feel like they are occurring in the present (e.g., in the case of flashbacks or nightmares). In PTSD, although there is often a fear of future re-traumatization, intrusions are thematically related to past traumatic experience(s); they typically involve re-experiencing a traumatic event in some manner. Alternatively, obsessions are typically focused on the future, or they center on doubts about whether an event happened (Pinciotti, Fontenelle, et al., 2022). However, individuals with OCD may experience obsessions that are intrusive memories, including posttraumatic memories (Pinciotti, Fontenelle, et al., 2022). To distinguish between obsessions and re-experiencing symptoms, additional text in the PTSD section of the DSM-5-TR states that “In OCD, there are recurrent intrusive thoughts, but . . . the intrusive thoughts are not related to an experienced traumatic event” (APA, 2022). No such assertion is made in the chapter on OCD and, as shown in the above example, obsessions can relate to traumatic memories. As such, future-oriented intrusions or intrusions related to doubts about past experiences are more likely to be obsessions, whereas past-oriented intrusions specifically related to traumatic experience(s) are more likely, but not always, posttraumatic re-experiencing. Obsessions related to traumatic experience(s) are likely to only include elements of the experience (e.g., the number 54), whereas intrusions that are exclusively or almost exclusively about the traumatic experience(s) fit the definition of re-experiencing far better than of obsessions.

In some instances, obsessions and re-experiencing symptoms can also be distinguished by their triggers. In OCD, obsessions can be autogenous (emerging from within) or reactive (Keleş Altun et al., 2017; Lee & Kwon, 2003). Similar research has yet to be carried out on PTSD, but re-experiencing symptoms are typically defined as being reactive, although individuals with PTSD are often unaware of the triggers (Ehlers et al., 2004). As such, if the patient reports that their intrusions “come out of nowhere” and careful functional analyses fail to identify internal (e.g., related thoughts) or external triggers, this may suggest that the intrusions are an obsession rather than a posttraumatic re-experiencing symptom. Of course, given the lack of related empirical research, particularly on PTSD, this guidance should be used cautiously. In the case of reactive obsessions, the triggers are almost always thematically related to the obsessions (Lee & Kwon, 2003), which, as noted above, are usually related to common OC symptom subtypes. Similarly, re-experiencing symptoms are usually triggered by trauma reminders (Ehlers et al., 2004). Though less common, as noted in a case example above, reactive obsessions can also be triggered by trauma reminders (Gershuny et al., 2003).

Affect and Mood

Regardless of the content of the intrusions, obsessions and posttraumatic re-experiencing provoke similar distressing emotions, including anxiety, disgust, anger, shame, and guilt (Brake et al., 2019; Cândea & Szentagotai-Tătar, 2018; Whiteside & Abramowitz, 2005). Despite the removal of OCD and PTSD from the anxiety disorders chapter of previous versions of the DSM, anxiety plays a significant role in both disorders. Anxiety is explicitly, albeit briefly, included in the diagnostic criteria for OCD—intrusions “cause marked anxiety or distress (in most individuals)” (APA, 2022)—but is not mentioned in the diagnostic criteria for PTSD. Nonetheless, most patients with OCD or PTSD report chronic anxiety, and elevated levels of trait anxiety are common to both disorders (Emmelkamp & Ehring, 2014; Kampman et al., 2017).

Excessive shame and guilt are also common to OCD (Laving et al., 2023) and PTSD (APA, 2022). Although traumatic experiences can influence these emotions in both disorders, guilt, and shame are usually focused on trauma in PTSD and are only sometimes associated with trauma in OCD (Pinciotti, Fontenelle, et al., 2022). Shame or guilt that arises due to the content of intrusive thoughts (e.g., “because I have intrusive thoughts about harming my child, I am a terrible parent”) is common in OCD, especially when intrusive thoughts are deemed immoral, repugnant, or taboo (e.g., aggressive or sexual obsessions; Visvalingam et al., 2022). Such instances are common among OCD patients with scrupulosity obsessions, but recent work does suggest that scrupulosity may also influence posttraumatic stress symptoms, particularly among individuals exposed to sexual assault (Jones et al., 2023). In PTSD, posttraumatic shame is more commonly experienced by those exposed to sexual assault than those exposed to physical assault, a transportation accident, or illness/injury (Amstadter & Vernon, 2008). Conversely, associations between guilt and PTSD symptoms appears to be strongest for individuals who have experienced combat trauma or medical/illness-related trauma (Kip et al., 2022).

Depressive symptoms and comorbid major depressive disorder (MDD) are common in both OCD and PTSD (Breslau et al., 2000; Ruscio et al., 2010). However, symptoms of depressed mood or anhedonia that begin or worsen after a traumatic event are diagnostic criteria for PTSD (APA, 2022). These negative alternations in mood can arise from an internal sense of emotional disconnection and detachment from others that often follows trauma (Pinciotti, Fontenelle et al., 2022). Individuals with OCD and PTSD may appear to experience diminished interest in activities due to a lack of engagement in said activities. However, interest often remains but is in competition with other factors (e.g., intrusions or anxiety) that motivate avoidance. Some OCD patients may also substantially reduce engagement in enjoyed activities because compulsive behaviors take hours per day (APA, 2022). Accordingly, there can be value in assessing the functions of reduced engagement in enjoyable activities as this can reveal information that may inform differential diagnosis of OCD, PTSD, or comorbid depression.

Arousal

Given that OCD and PTSD involve dysfunction of the autonomic nervous system (Olbrich et al., 2022; Schneider & Schwerdtfeger, 2020), hyperarousal symptoms are also common. For example, some research suggests that individuals with either condition may exhibit hypervigilance (APA, 2022; Merritt & Purdon, 2022), increased attention toward and difficulty disengaging from threat cues (Cludius et al., 2019; Fani et al., 2012), and difficulties with sleep (Cox et al., 2020; McNally et al., 2014). Hypervigilance and increased alertness regarding fear cues within OCD and PTSD can be differentiated by their triggers (i.e., obsessions or re-experiencing) and focus (i.e., obsession-related or trauma-related).

Sleep disturbances are common to many psychiatric disorders, including OCD and PTSD (Boland & Ross, 2015; Segalàs et al., 2021; Werner et al., 2021). However, sleep disturbances are part of the diagnostic criteria for PTSD but not OCD (APA, 2022). Sleep disruptions in PTSD are commonly associated with reminders of the traumatic event. This includes, but is not limited to, sleep disruption resulting from re-experiencing symptoms (e.g., nightmares) and fear of letting one’s guard down during sleep, thereby increasing the perceived risk of harm (Werner et al., 2021). Alternatively, sleep disruptions in OCD are often associated with obsessions and some compulsions, namely checking (Timpano et al., 2014; Wong et al., 2022). Checking compulsions at night is not uncommon in OCD and can look quite similar to checking behaviors seen in PTSD (e.g., checking doors and windows to ensure they are locked). Checking can disrupt sleep in both cases, particularly if the checking behaviors take a large amount of time (Nicolas, 2008; Werner et al., 2021). Accordingly, functional analysis of sleep disturbances can reveal clues as to whether they are functionally related to reminders of a traumatic event or to obsessions and/or compulsive behaviors. Similarly, a review of symptom history can be used to determine temporal associations between sleep disturbance and trauma exposure (Pinciotti, Fontenelle, et al., 2022). If sleep issues started or significantly worsened after trauma, then they are likely related to PTSD. If they existed prior to trauma exposure or were unchanged by trauma exposure, then they can be related to any number of psychiatric disorders, including OCD.

Avoidance and Safety Behaviors

OCD and PTSD are characterized and maintained by excessive avoidance, escape behaviors, and safety behaviors (APA, 2022). In both disorders, environmental triggers, aversive thoughts, and negative emotions are commonly avoided or escaped, and safety behaviors are carried out to prevent or reduce intrusive thoughts, emotional distress, and risk of feared outcomes (Pinciotti, 2023). In OCD, safety behaviors are also commonly performed to obtain a sense of certainty (Salkovskis, 1991) or to suppress pathological doubt about one’s recalled experience (Pinciotti, Fontenelle, et al., 2022).

Commonly used safety behaviors in OCD include but are not limited to checking, cleaning, and ordering and arranging (Pinto et al., 2008). Similar behaviors can present in individuals with PTSD and can appear almost indistinguishable from common compulsions. An individual with PTSD, for example, might repeatedly check door locks or visually “sweep” rooms to ensure safety and prevent revictimization. Following sexual victimization, it is common for survivors to engage in cleaning and washing behaviors (Badour et al., 2012; Fairbrother & Rachman, 2004; Tipsword et al., 2023). Like compulsive washing or cleaning among OCD patients with contamination obsessions, excessive washing behaviors in PTSD can persist well after any trace of the original contaminants remains (Fairbrother & Rachman, 2004). Interestingly, research suggests that such washing behaviors are partially motivated and maintained by the same underlying mechanisms that motivate washing compulsions, namely disgust and mental contamination (Badour et al., 2012; Fairbrother & Rachman, 2004).

Some safety behaviors are conceptualized as avoidance, for example, only driving or shopping at certain times, with certain people, or at certain locations (Salkovskis, 1991). The individual is indeed avoiding the “sensible” or more convenient option (e.g., shopping alone), but the replacement behavior (e.g., shopping with a friend) can be considered a safety behavior. These types of behaviors are common to many anxiety and related disorders, including OCD and PTSD, but the motivations are often distinct. For example, both patients with OCD and those with PTSD may choose to shop at a “safe store” after hours to avoid crowds. However, the patient with PTSD may do this to reduce the risk of re-traumatization, whereas the OCD patient may do this to avoid contracting illness or infecting others.

The degree to which avoidance and safety behaviors factually relate to feared outcomes can often differ between OCD and PTSD. In PTSD, avoidance and safety behaviors tend to be realistically related to the trauma or risk reduction for re-traumatization (e.g., checking the stove after experiencing a house fire; Pinciotti, 2023), though the perceived likelihood that the behavior will prevent re-traumatization is commonly inflated. Avoidance and safety behaviors can also be realistic but overestimated in OCD, but such behaviors are often linked with superstitious beliefs, magical ideation, and thought-action fusion (Einstein & Menzies, 2004; Shafran et al., 1996). To our knowledge, research has yet to test if such magical beliefs or thought-action fusion are more common in OCD than PTSD, but studies have failed to find significant differences between OCD and other anxiety disorders (Agorastos et al., 2012; Thompson-Hollands et al., 2013).

Excessive and ritualized behaviors in PTSD can be difficult to distinguish from compulsions. In PTSD, safety behaviors are often performed until the individual has established an improved sense of safety (Pinciotti, 2023). This can also be true in OCD, but compulsions are also often performed according to a rigid or ritualized set of rules until a feeling of completeness, perfection, or “just right” has been obtained or until a sense of certainty has been achieved (Pinciotti, 2023). Given the nebulous nature of these feelings, they are often not obtained or inadequately felt. Although the need for “just right” or completeness is common in the general population, it appears to be particularly characteristic of OCD compared to other emotional disorders (Belloch et al., 2016; Sica et al., 2015), whereas it has not, to our knowledge, been examined in PTSD.

As with intrusions, clinicians should examine the temporal precedence and the content of safety behaviors in relation to traumatic experience(s) (Pinciotti, Fontenelle, et al., 2022). For example, if a patient started checking stoves after a house fire, these behaviors may be better explained by hypervigilance symptoms of PTSD than compulsive behaviors in OCD. However, if the same individual began engaging in compulsive behaviors that are unrelated to their trauma history (e.g., arranging or counting) alongside checking, their symptoms may be better explained by OCD or comorbid PTSD and OCD (Pinciotti, Fontenelle, et al., 2022). Moreover, if the same individual engaged in significant checking behaviors (or other common compulsions) prior to the traumatic event and checking behaviors worsened or changed focus following the trauma, then a diagnosis of OCD should be considered (Pinciotti, Fontenelle, et al., 2022).

Risky or self-destructive behaviors can occur in many disorders and are listed as diagnostic criteria for PTSD (APA, 2022). In both OCD and PTSD, such externalizing behaviors can function as forms of avoidance or safety behaviors. In PTSD, risky and self-destructive behaviors may be thrill-seeking behaviors but may also be used to counteract unwanted thoughts or negative affect (Contractor et al., 2017). For example, a patient with PTSD may engage in unprotected sex as a means of avoiding trauma-related memories and emotions (Weiss et al., 2019), or sex with multiple partners as a way of establishing a sense of control and bodily autonomy (O’Callaghan et al., 2018). In OCD, risky behaviors may be conceptualized as “testing” or reassurance behaviors intended to obtain certainty about the likelihood that one might engage in or enjoy a feared behavior. For example, an OCD patient may hold a knife to oneself to test if they will harm themself or engage in risky sex to test if they will contract a sexually transmitted infection (e.g., case example KK; Pinciotti, 2023).

Memory Disturbances

Many patients with PTSD report an inability to recall specific details related to a traumatic event (APA, 2022). Consistent with cluster D criteria for PTSD, trauma-related memory disturbance may occur due to dissociative amnesia (APA, 2022), or because the trauma itself has disrupted the encoding or consolidation of memories, resulting in memory fragmentation (Brewin, 2011, 2014; Crespo & Fernández-Lansac, 2016; Layton & Krikorian, 2002; Rubin et al., 2008). Consistent with cluster C criteria for PTSD, reported memory disturbances following trauma may also reflect the patient’s attempts to avoid salient details of the memory (APA, 2022). To be clear, it is normal to avoid thinking or talking about traumatic experiences, but more extreme and persistent avoidance may be indicative of PTSD. Use of chart review, other reports from partners or custodians, or repeated assessment over time as rapport develops and symptoms improve can provide insights into the degree to which a patient has difficulty recalling details of a traumatic event or is avoiding the memories, both of which may provide preliminary evidence of PTSD.

In OCD, memory disturbances are often not true disturbances but simply memory distrust (Dar et al., 2022). Repeated interactions with an object or scenario (e.g., repeated stove checking) are associated with poorer memory vividness, detail, and confidence (van den Hout & Kindt, 2003). As such, hours spent performing specific compulsions can diminish memory vividness, thus resulting in poorer confidence that the compulsion was adequately completed (Radomsky et al., 2006). Though yet to be tested, this may also apply to mental checking. It is not yet clear if memory vividness, detail, or confidence are influenced by the frequency of recollections of a traumatic experience or associated safety behaviors (e.g., checking) in PTSD.

Differential Diagnosis: Assessment Recommendations

Assessments to simultaneously measure OCD and PTSD symptoms or focus on their overlap are lacking. Those that do include assessment modules for both disorders lack nuanced instruction for differential diagnosis, have yet to be empirically validated, or have yet to demonstrate adequate psychometric properties for modules devoted to one of the two diagnoses. Furthermore, well-validated self-report measures for OCD and PTSD individually have been shown to include items that capture symptoms from both disorders (Franklin & Raines, 2019; Huppert et al., 2005). These OCD and PTSD items are endorsed together at high rates (Franklin & Raines, 2019; Huppert et al., 2005), calling into question the discriminant validity of these measures, particularly among individuals with suspected OCD and PTSD. This represents a notable gap in the assessment literature, given the high comorbidity between OCD and PTSD and the similarities in symptom presentation and function across these disorders (Pinciotti, Fontenelle, et al., 2022; Pinciotti, Horvath, et al., 2022; Pinciotti & Orcutt, 2020; Pinciotti, Wetterneck, et al., 2022). Despite these limitations, many excellent measurement tools exist to assess symptoms of OCD and PTSD separately that can be reasonably expected to effectively distinguish between disorders when administered with minimal augmentation and supplemented with evidence-based unstructured interviewing and clinical judgment (as detailed in the previous sections).

In the following sections, we highlight broadband diagnostic interviews, as well as one recommended self-report measure and one recommended clinician-administered assessment tool for each diagnosis, chosen for their psychometric properties and widespread use. Limited information regarding other assessment tools can be found in these sections and in the supplemental files (see Supplemental Tables S1–S3).

Structured Diagnostic Interviews for OCD and PTSD

Multiple clinician-administered clinical interviews designed to establish diagnoses for DSM-5 psychiatric disorders include modules for OCD and PTSD. Commonly used interviews include the Diagnostic Interview for Anxiety, Mood, and OCD and Related Neuropsychiatric Disorders (DIAMOND; Tolin et al., 2018), the Structured Clinical Interview for DSM-5 (SCID-5; First et al., 2016), the Anxiety Disorders Interview Schedule for DSM-5 (ADIS-5; Brown & Barlow, 2014), and the Mini International Neuropsychiatric Interview for DSM-5 (MINI 7.0.2; Sheehan et al., 1998).

Although the DIAMOND for DSM-5 has demonstrated excellent psychometric properties for most diagnostic modules, insufficient data were available to validate the PTSD module (Tolin et al., 2018). However, the DIAMOND may be preferred over alternatives as it is freely available (Tolin et al., 2018). Preliminary psychometric evaluation of the SCID-5 suggests good to excellent interrater and test–retest reliability for both OCD and PTSD modules; however, these studies have involved small OCD and PTSD samples and translated versions of the assessment (Osório et al., 2019; Shabani et al., 2021; Shankman et al., 2018). The DSM-5 versions of the ADIS and MINI have not yet been validated, though both are very similar to their previous versions, developed and validated for DSM-IV (Brown et al., 1994; Sheehan et al., 1998). Despite this significant limitation, the MINI may still be preferred in some settings for its brevity (15-20 minutes) when compared to the DIAMOND, SCID-5, and ADIS-5, which often take upward of an hour to complete.

Structured Assessment of OCD

A variety of self-report and clinician-administered tools can be used to characterize OCD symptoms. The Dimensional Obsessive-Compulsive Scale (DOCS; Abramowitz et al., 2010) is a self-report tool offering a stable 4-factor structure to assess the severity of empirically supported OCD symptom dimensions. Moreover, the dimensional structure allows the DOCS to avoid arbitrarily conflating symptom severity with the number or type of obsessions and compulsions endorsed (Abramowitz et al., 2010). The DOCS demonstrates high internal consistency (α = .89–.91), 12-week test–retest reliability (r = .66), convergent validity (r = .54–.71), and discriminant validity (r = .08–.52), and it is sensitive to treatment effects (Abramowitz et al., 2010; Mahoney et al., 2014; Thibodeau et al., 2015). The DOCS demonstrates good sensitivity and specificity; a cutoff score of 21 is appropriate to distinguish OCD patients from individuals with other anxiety disorders (70% sensitivity and specificity), and a cutoff score of 18 is appropriate to distinguish OCD patients from nonclinical adults (78% sensitivity and specificity; Abramowitz et al., 2010).

A study examining differences in self-reported OCD and PTSD symptoms among military veterans diagnosed with PTSD related to military sexual trauma found that, despite only 7.7% of the sample meeting criteria for comorbid OCD, 74% screened positive for probable OCD based on DOCS cut-scores (Franklin & Raines, 2019). Unfortunately, the authors of this paper did not report if a cutoff of 18 or 21 was used. This same study also reported that the correlation between the DOCS and the PTSD Checklist for DSM-5 (PCL-5; Blevins et al., 2015) was quite high (r = .60). These data suggest that the specificity of the DOCS is poor when distinguishing between PTSD and OCD and that the discriminant validity of the DOCS is poor when compared with a self-report measure of PTSD.

Despite being time-consuming (upwards of an hour in many cases) and insufficient to determine a diagnosis of OCD, the Yale-Brown Obsessive-Compulsive symptom (Y-BOCS) checklist and severity scales (Goodman, Price, Rasmussen, Mazure, Delgado, et al., 1989; Goodman, Price, Rasmussen, Mazure, Fleischmann, et al., 1989) have been the gold-standard clinician assessments for adult OCD for more than 40 years (Antony et al., 2001; Frost et al., 1995). The Y-BOCS exhibits good reliability as demonstrated by its high internal consistency (α = .69; Goodman, Price, Rasmussen, Mazure, Delgado, et al., 1989) and test–retest reliability (r = .61–.97; López-Pina et al., 2015), and it is sensitive to treatment effects (McGuire et al., 2012). The Y-BOCS exhibits moderate to high convergent validity (r = .67–.74; Goodman, Price, Rasmussen, Mazure, Delgado, et al., 1989), but fair to poor discriminant validity when compared with measures of anxiety (r = .47–.85) and depression (r = .53–.91; Goodman, Price, Rasmussen, Mazure, Delgado, et al., 1989; Grabill et al., 2008; Storch et al., 2005; Taylor, 1995). A total Y-BOCS score of 14 has demonstrated excellent sensitivity (91%–94%) and modest to adequate specificity (62%–78%) for detecting OCD (Cervin et al., 2022). Discriminant validity of the Y-BOCS relative to PTSD scales has not been reported in the literature, and it is not yet known if any Y-BOCS cut-scores provide adequate specificity to distinguish between OCD and PTSD.

The second edition of the Y-BOCS (Y-BOCS-II; Storch, Larson, et al., 2010; Storch, Rasmussen, et al., 2010) and the Dimensional Y-BOCS (DY-BOCS; Rosario-Campos et al., 2006) are viable alternatives to the original Y-BOCS (Hiranyatheb et al., 2014; Kim et al., 1994; Melli et al., 2015; Storch et al., 2005; Storch, Rasmussen, et al., 2010; Wu et al., 2016). See supplemental Table S1 for additional information about assessments for OCD.

Structured Assessment of PTSD

Assessment of PTSD begins with the identification of a Criterion A stressor (i.e., the index trauma) to which posttraumatic symptoms are anchored. The Life Events Checklist for DSM-5 (LEC-5; Weathers et al., 2013) is a commonly used measure that assesses for lifetime exposure to potentially traumatic experiences. The LEC-5 evaluates exposure to 16 potentially traumatic experiences per DSM-5 criteria (e.g., “Happened to me,” “Witnessed it,” “Learned about it,” etc.). There are three versions of the LEC-5: the standard self-report, the extended self-report (which establishes the worst event among endorsed items), and the interview. While the updated LEC-5 has yet to be psychometrically evaluated, it remains largely unchanged from the original LEC, which displays good psychometric properties (Gray et al., 2004).

The most used self-report symptom severity measure for PTSD is the 20-item PCL-5 (Blevins et al., 2015). The PCL-5 displays good internal consistency (α = .83–.97) and test–retest reliability (r = .58–.91), and it is sensitive to treatment effects (Forkus et al., 2023; Wortmann et al., 2016). The PCL-5 exhibits moderate to strong convergent validity (r = .44–.89), and fair to good discriminant validity when compared with depression (r = .60–.64) and anxiety (r = .40–.61; Forkus et al., 2023). Recommended cutoff scores have ranged from 22 to 49, with the majority falling between 31 and 33 (Forkus et al., 2023). Across studies, the PCL-5 has demonstrated variable sensitivity (.50–1.00) and specificity (.35–.97) for detecting PTSD (Forkus et al., 2023). For example, with a cutoff score of 37, it has demonstrated good sensitivity (.66) and specificity (.97) as a screener for probable past-month and lifetime PTSD among undergraduates (Blevins et al., 2015). Data from the aforementioned veterans study suggest that the PCL-5 does not have adequate discriminant validity when compared to measures of OCD, namely, the DOCS (Franklin & Raines, 2019). To our knowledge, research has yet to test if any PCL-5 cut-scores have adequate specificity when distinguishing between individuals with OCD and those with PTSD.

The gold-standard assessment for PTSD per DSM-5 criteria is the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5; Weathers et al., 2013). It can be used in combination with the LEC-5 to diagnose lifetime or past-month PTSD and assess for global symptom severity and specific symptom clusters (Weathers et al., 2018). The CAPS-5 has demonstrated excellent internal consistency (α = .81–.88) and test–retest reliability (κ = .83), and it is sensitive to treatment effects (Marx et al., 2022; Weathers et al., 2018). The CAPS-5 exhibits moderate to high convergent validity (r = .66–.83) and moderate to high discriminant validity when compared with related constructs (r = .33–.54; Weathers et al., 2018). However, one shortcoming of the CAPS-5 is its lengthy administration time (45–60 minutes). In many cases, this is not feasible, particularly when planning to use a PTSD assessment in combination with broadband diagnostic interviews and assessments for other psychiatric disorders such as OCD. In such cases, the PTSD Symptom Scale Interview (PSSI-5; Foa & Capaldi, 2013), with an administration time of 20 to 25 minutes, may be preferred.

The PSSI-5 can be used to diagnose past-month PTSD and assess for past-month and past-2-week global symptom severity and severity of specific symptom clusters (Foa et al., 2016). The PSSI-5 also has good internal consistency (α = .89), test–retest reliability (r = .87), convergent validity (r = .72–.85), and discriminant validity (r = .62–.73; Foa et al., 2016). To our knowledge, research has yet to determine the discriminant validity of the CAPS-5 or the PSSI-5 relative to OCD measures, or to determine whether cut-scores for either measure provide adequate specificity to distinguish between OCD and PTSD. See supplemental Table S2 for additional information about assessments for PTSD.

OCD and PTSD Assessment Recommendations

The following recommendations apply to the evaluation of a variety of clinical presentations: cases where comorbid OCD and PTSD are suspected, cases of OCD with a significant trauma history or subclinical symptoms of PTSD, and cases of PTSD with evidence of obsessions or compulsions. Some recommendations are admittedly time-consuming and are provided as “best case scenario” guidance with the understanding that many assessors, clinicians, and patients may not have time to complete the full battery. Nonetheless, the following recommendations should aid clinicians and assessors who wish to obtain a differential diagnosis, accurately categorize symptoms as “belonging to” OCD, PTSD, or both diagnoses, and characterize the influence of trauma on OCD symptoms.

In most circumstances, screening tool(s) will help to determine if diagnoses of OCD and/or PTSD are likely and can guide or supplement unstructured clinical interviews. Screening tools could include the DIAMOND self-report screener or SCID-5 screening interview, which cover a range of common psychiatric disorders, including OCD and PTSD. If OCD or PTSD are suspected, then the brief self-report Obsessive-Compulsive Inventory (OCI-4; Abramovitch et al., 2021) and Primary Care PTSD Screen for DSM-5 (PC-PTSD-5; Prins et al., 2016) may be preferred, both of which have surprisingly strong psychometrics considering their brevity. However, the PC-PTSD-5 provides a list of potentially traumatic events along with a single question to screen for Criterion A trauma (“Have you ever experienced this kind of event?”). Like other trauma screeners included in broadband diagnostic interviews and the PSSI-5, this is not nearly as thorough as the LEC-5. As such, we recommend the administration of the LEC-5 as part of screening procedures.

Based on results from the screening, administer all or parts of a broadband structured clinical interview, such as the DIAMOND, SCID-5, ADIS-5, or MINI, to establish DSM-5 diagnoses. If DSM-5 Criterion A trauma(s) or significant posttraumatic stress symptoms are reported in the screening, then the CAPS-5 or PSSI-5 can be administered in lieu of the PTSD module in the broadband diagnostic interview. This is especially true if administering the DIAMOND, which lacks psychometric data on the PTSD module (Tolin et al., 2018), or MINI, which lacks any published psychometric data. If a diagnosis of OCD is confirmed or suspected or if significant obsessions or compulsions are reported during screening or the diagnostic interview, then complete the clinician-administered Y-BOCS symptom checklist and severity scales. Finally, the OCD Trauma Timeline Interview (OTTI; Wadsworth et al., 2021) can be included if the assessor wishes to obtain additional information about associations between the patient’s trauma, OCD symptoms, and PTSD symptoms (see OTTI section below). Importantly, these assessments should be administered with consideration of the information outlined earlier in the manuscript on the connectivity between OCD and PTSD.

CAPS-5 and PSSI-5 Considerations

The CAPS-5 is a structured interview involving specific questions in a predetermined order, with limited room for deviation. Prompts are intended to be read verbatim, although the instructions state that if additional information is needed following the use of standard prompts, assessors can follow-up with their own questions (Weathers et al., 2013). Empirical data on the discriminant validity of the CAPS-5 among individuals with OCD and PTSD symptomatology does not yet exist. However, given problems with inflated scores and item overlap among other assessment tools (Franklin & Raines, 2019; Huppert et al., 2005; Pinciotti & Orcutt, 2020), it is reasonable to suspect that additional follow-up questions aimed at differentiating OCD and PTSD symptoms might be needed among this specific population. Importantly, this level of adjustment to the standard interview language may impact the assessment’s psychometric properties, as it was not designed for this level of flexibility. Alternatively, the PSSI-5 is a semistructured interview that was designed to be adaptable to individual client characteristics and responses. Thus, the addition of questions aimed at distinguishing OCD from PTSD is more consistent with its intended use. This benefit of the PSSI-5, in combination with its shortened administration time, may enhance its appeal relative to the CAPS-5, especially if significant time was devoted to Y-BOCS administration. Nevertheless, some clinicians may prefer to use the gold-standard CAPS-5 with additional clarifying questions as needed.

Administration of the CAPS-5 and PSSI-5 begins with the selection of a Criterion A trauma, to which all other symptoms are anchored. The CAPS-5 is typically paired with a trauma checklist, such as the LEC-5, to identify the worst Criterion A trauma, whereas the PSSI-5 includes its own trauma screen. In both cases, assessors are instructed to ask about symptoms as they relate to the chosen trauma. Many of the CAPS-5 questions are worded such that the trauma is specified, and assessors are instructed to use the client’s own language to label the trauma (Weathers et al., 2013). Many of the PSSI-5 questions simply refer to “the trauma.” While either method of referring to the trauma is acceptable, assessors should ensure that endorsed symptoms are, in fact, anchored to the past Criterion A trauma, particularly when assessing individuals with OC symptoms or suspected OCD. As such, it may be preferrable to ask PSSI-5 questions in a similar manner as CAPS-5 questions (i.e., anchor to a specific description of the event instead of a generic reference to “the trauma”).

When administering the CAPS-5 and, when deemed appropriate for the PSSI-5, assessors should use wording that is consistent with the respondent’s description of the traumatic event. For example, saying, “. . .when something reminded you of the time you were mugged,” as opposed to, “. . .when something reminded you of being physically assaulted.” Another option is to explicitly label the index trauma with a specific timeframe (e.g., “the mugging in 2010” or “the car accident in high school”) when anchoring symptoms to trauma(s). Specific phrasing and anchoring can help to limit the endorsement of physiological arousal related to intrusions (including obsessions) about a feared future assault. If distinctions between symptoms related to a past traumatic experience or future feared experiences are unclear, additional follow-up questions may be needed.

While the CAPS-5 and PSSI-5 assess avoidance and hypervigilance, only one question from each explicitly assesses safety behaviors. If an individual endorses hypervigilance symptoms, suggested follow-up questions include “What kinds of things do you do when you are alert or on-guard?” and “Is there anything you do to help you feel safer?” Similar follow-up questions are warranted following endorsement of avoidance symptoms (e.g., “What kinds of things do you do to avoid thoughts or feelings about [EVENT]?”). When hypervigilant or avoidant behaviors are endorsed, assessors should inquire about their triggers, how frequently they are repeated, and at what point an individual feels they are complete. Similarly, endorsement of memory difficulties should be followed with questions to distinguish memory disturbance from pathological doubt or memory distrust (e.g., “Are there some details that you don’t remember at all?” or “Are there details that you remember, but worry whether you are remembering them correctly?”), and to assess for reassurance-seeking (e.g., “Do you repeatedly ask others for reassurance about certain aspects of [EVENT], such as whether they think it was your fault or there was something you could have done to prevent it?”) and mental checking (e.g., “Do you intentionally go over details of the event in your mind over and over again?”). Endorsement of pathological doubt, reassurance-seeking, or mental checking could suggest the presence of OCD symptoms, and follow-up questions about their functions would be warranted, either during the assessment of PTSD symptoms or when assessing OCD symptoms (see below).

Care should be taken when assessing negative beliefs about the self, others, and the world to ensure that they are (as the DSM-5 criteria specifies), associated with the traumatic event, and began or worsened following the trauma. While the CAPS-5 includes questions to evaluate these specifications, the PSSI-5 does not. In addition, an individual who develops trauma-related OCD may endorse negative beliefs about themself due to their OC symptoms or comorbid depression. Thus, clarifying questions related to content and temporal relations to the traumatic event should be used to parse beliefs consistent with PTSD (e.g., “I am a bad person because of my role in the trauma,” or “Because of what happened, I am damaged”) and OCD (e.g., “I am a bad person because of my immoral thoughts,” or “Because of my compulsions, there is something seriously wrong with me”). In the case of negative beliefs that could fit either diagnosis (e.g., “The world is dangerous”), assessors should use information about the temporal relation to the Criterion A trauma to inform whether these beliefs are likely to be symptoms of OCD, PTSD, or other anxious psychopathology.

One disadvantage of administering the Y-BOCS symptom checklist after the CAPS-5 or PSSI-5 is that the assessor would have limited information about the patient’s specific obsessions and compulsions that could be used to ask clarifying questions when assessing for PTSD. For example, if a patient reported a motor vehicle accident as an index trauma on the chosen trauma screener and it was only later found out (during Y-BOCS administration) that the patient also experiences aggressive obsessions related to driving their car into oncoming traffic and, then the assessor may not know to adjust their language and ask clarifying questions during PTSD assessment to better ensure that answers to posttraumatic intrusion questions are not incidentally capturing aspects related to the patient’s aggressive obsessions. This example case would be even more difficult if the patient met criteria for OCD and PTSD, but OCD symptoms did not emerge or reach diagnostic threshold until after the car accident. In such scenarios, anchoring CAPS-5 or PSSI-5 questions to the patient’s index trauma may not be sufficient to ensure that the symptoms being reported are in fact PTSD symptoms and not OCD symptoms.

Y-BOCS Considerations

The Y-BOCS symptom checklist contains a list of dozens of obsessions and compulsions, in addition to several related phenomena that may or may not be obsessions or compulsions. Unfortunately, these additional items do not relate to trauma or PTSD; they are primarily concerned with tics and symptoms of other obsessive-compulsive and related disorders. That said, the Y-BOCS checklist is meant to be a semistructured interview, so it is incumbent on the assessor to modify phrasing, provide relevant examples, and ask probing questions to determine if endorsed items are indeed obsessions or compulsions as opposed to subclinical symptoms or symptoms associated with other disorders. These instructions will improve the quality of Y-BOCS assessment regardless of the presence or absence of comorbidities, including PTSD.

When assessing OCD patients with a significant trauma history or suspected PTSD, the assessor may wish to begin by modifying the instructions to better ensure that the patient knows the nuanced differences between obsessions and re-experiencing symptoms. If the CAPS-5 or PSSI-5 was administered before the Y-BOCS, then this might be accomplished by first defining obsessions (as described in the general instructions of the Y-BOCS) and then clarifying that previously reported re-experiencing symptoms are not obsessions (e.g., “Even though they are distressing images that occur against your will, the intrusive recollections about the mugging you experienced are technically not obsessions. They are called posttraumatic intrusions or re-experiencing symptoms. The following questions about obsessions are not meant to evaluate your re-experiencing symptoms”).

When administering specific Y-BOCS checklist items, specific examples of common obsessions and compulsions should be used instead of simply reciting the prompts verbatim. For example, when assessing for horrible, intrusive images, which could easily be confused for re-experiencing symptoms, the assessor could specify, “such as images of friends or family dying or being harmed or your house burning down.” Unless specific obsessions or compulsions are spontaneously shared by the patient, then endorsement of Y-BOCS checklist items should be followed with open-ended questions (e.g., “can you describe that for me?”). This should not only provide information about the patient’s specific obsessions (as opposed to obsession categories) but could also help to ensure that, for example, aggressive obsessions are not being endorsed due to the presence of traumatic re-experiencing symptoms. Importantly, there will be instances when a patient’s symptoms do not exclusively fit the DSM-5 diagnostic boundaries of OCD or PTSD. Some symptoms may reasonably be conceptualized as related to either disorder.

When administering the Y-BOCS severity scales, it is critical to anchor the severity items to specific obsessions and compulsions or symptom clusters endorsed on the checklist. As such, careful administration of the checklist is crucial to the validity of the severity scales, especially when assessing patients with comorbid conditions that can have significant symptom overlap with OCD, such as PTSD. Of note, the self-report version of the Y-BOCS should be administered with caution when used to assess OCD symptoms of patients with comorbidity such as PTSD, as it is easy to conflate symptoms of both disorders (Franklin & Raines, 2019; Huppert et al., 2005). It is the authors’ opinion that the self-report Y-BOCS should not be used in such cases unless the severity scales are clearly anchored to specific obsessions and compulsions, and the assessor can confirm the patient understands these anchors. This can be accomplished in many cases by waiting to administer the self-report version until after the clinician-administered Y-BOCS has been successfully completed and by providing the patient with explicit details about their obsessions and compulsions as written instructions or a brief conversation before they complete the questionnaire. If self-report questionnaires are being administered online, then this can be accomplished with simple code that pipes patient-specific details into questionnaire instructions. For example, if the patient endorsed contamination concerns related to dirt, germs, and illness as their primary obsession, then the instructions of the obsessions section of the Y-BOCS-SR could be modified to ask the patient to answer the following questions based on their “contamination concerns related to dirt, germs and illness.”

The OTTI

The recently developed OTTI is a primarily qualitative interview designed to assess associations between trauma, OCD, and PTSD with respect to onset, relative vulnerabilities, symptom overlap, and functional connections. The OTTI involves psychoeducation about the differences between OCD and PTSD symptoms, as well as several items specifically designed to address the functional overlap of OCD and PTSD. These features set the OTTI apart from extant measures. For example, patients are asked: “Do you believe your OCD and trauma are linked in any way? If yes, how do you think they are linked?,” and “If your OCD disappeared tomorrow, how do you think that would shift your experience of your trauma symptoms?” Patients are also asked whether and how they believe that their OCD behaviors serve as a coping mechanism for their trauma-related experiences. This semistructured interview is ideal for clinical settings in which providers need to ascertain the ways in which OCD and trauma-related symptoms may be intertwined. This information may inform treatment planning with regards to how best to address these related symptoms. For example, the OTTI may reveal that obsessions and compulsions have a clear linkage to traumatic experience(s), which might suggest imaginal exposure to traumatic memories is indicated. Alternatively, the OTTI could also reveal that posttraumatic stress symptoms are partially maintained by compulsive behaviors (e.g., lock checking), which could be addressed with in vivo exposure (leave windows unlocked at night) and response prevention (without checking).

Self-Report Assessments

Self-report measures should be used with caution in cases of suspected comorbid OCD and PTSD or symptom overlap. As described above, a study among veterans with military sexual trauma found that items from the DOCS and PCL-5, paired based on similar thematic content (e.g., avoidance of intrusions), were endorsed together at high rates, and that the total scores of these measures were highly correlated (Franklin & Raines, 2019). Furthermore, total scores of two additional self-report measures, the Obsessive-Compulsive Inventory (OCI; Foa et al., 1998) and the Posttraumatic Diagnostic Scale (PDS; Foa et al., 1997), were found to be significantly correlated among individuals with OCD (r = .31), PTSD (r = .32), and other anxiety disorders (r = .49), as well as undergraduates (r = .59; Huppert et al., 2005). Expert psychologists evaluated items from the OCI and PDS for their potential to capture symptoms from the alternative diagnosis (Huppert et al., 2005). The experts determined that 20 of the 42 OCI items and 14 of the 17 PDS items possibly or definitely overlap with typical PTSD and OCD symptoms, respectively. These findings suggest that these self-report measures may only partly distinguish between OCD and PTSD symptoms and that some patients can have difficulty making this distinction.

If self-report tools are to be used in cases with comorbid OCD and PTSD, then assessors are advised to first establish diagnoses with other tools, provide the patient with adequate psychoeducation about key distinctions between OCD and PTSD, and evaluate the patient’s understanding of these distinctions. Data thus far suggest that cutoff scores should not be used or should be used with extreme caution if attempting to distinguish between OCD and PTSD. Relatedly, interpretation of DOCS and PCL-5 scores should be interpreted cautiously, given robust correlations between these self-report tools (Franklin & Raines, 2019).

Future Directions

Despite the myriad of excellent assessment tools for OCD and PTSD, there are limitations to their uses, particularly among individuals with some combination of a trauma history, obsessions and/or compulsions, and posttraumatic stress symptoms. Apart from the OTTI and, to a lesser degree, broadband diagnostic interviews, there is a lack of instruments designed to evaluate overlapping symptoms of OCD and PTSD. Broadband diagnostic interviews have not been validated for their discriminant validity among individuals with overlapping obsessive-compulsive and posttraumatic symptomatology, and most lack psychometric validation based on current, DSM-5 criteria for OCD and PTSD. Furthermore, popular self-report measures that have been validated and are psychometrically sound measures of OCD and PTSD individually lack nuance to help patients or clinicians differentiate between OCD and PTSD symptoms (Franklin & Raines, 2019; Huppert et al., 2005). Future research is needed to (1) obtain nationally representative prevalence rates of OCD, PTSD, and comorbid OCD and PTSD based on current, DSM-5 criteria, (2) evaluate the psychometrics of key clinician-administered and self-report tools for OCD and PTSD, with a focus on discriminant validity between OCD and PTSD assessments and sensitivity and specificity of cut-scores between individuals with OCD and PTSD, and (3) develop additional tools designed specifically to address overlapping symptoms and functional connectivity between OCD and PTSD.

Pinciotti and Wadsworth (2023) are piloting the Post-Traumatic Obsessive-Compulsive Scale (P-TOCS), a self-report measure designed to evaluate phenotypically and functionally similar symptoms of OCD and PTSD among individuals with co-occurring OCD and PTSD, trauma-exposed individuals with OCD, and individuals with PTSD who endorse subclinical obsessions or compulsions. Specifically, the P-TOCS has adapted items from existing OCD and PTSD measures that have demonstrated overlapping content and are endorsed together at high rates to include more nuance. If successful, the P-TOCS may provide a measure that can aid in the parsing of posttraumatic and OC symptoms, improve diagnostic accuracy, and assist with case conceptualization and treatment planning. A self-report version of the OTTI is also being piloted and will make collection of this information more feasible in research or clinical contexts that have limited time for clinician-administered assessments (Pinciotti & Wadsworth, 2023).

While intrusions are primary to the diagnosis of OCD and PTSD, they are also relevant to many other psychiatric disorders. Despite this, no measures exist to assess the presence or severity of intrusions outside of the context of specific disorders (e.g., schizophrenia) or specific types of intrusions (e.g., hallucinations). Similar measures exist for a variety of other symptoms that cut across disorders (e.g., trait anxiety, depressed mood, behavioral inhibition). A measure devoted to the assessment of intrusions that is not developed for a specific disorder or type of intrusions could be of great benefit to the field. Such a measure could be particularly useful for clinicians employing transdiagnostic treatments for patients who experience intrusions across a range of disorders.

Currently available tools only provide minimal insight about safety behaviors in PTSD. This is likely due, at least in part, to the lack of emphasis placed on safety behaviors in PTSD by the DSM-5. Similarly, available tools pay limited attention to avoidance in OCD, which is likely a downstream consequence of the lack of emphasis on avoidance in the DSM-5 diagnostic criteria for OCD. Accordingly, measures that more effectively assess safety behaviors in PTSD and avoidance in OCD are needed. Such tools would benefit from the inclusion of instructions or procedures to aid assessors in evaluating the causes and functions of safety behaviors and avoidance and the degree to which these symptoms are unique to specific psychiatric disorder(s). Given the phenotypic and functional overlap of many avoidance and safety behaviors across OCD and PTSD, it may also be useful to create a measure that agnostically evaluates the presence and severity of these behaviors. Future research may also consider developing new self-report measures or adapting the Y-BOCS (Goodman, Price, Rasmussen, Mazure, Fleischmann, et al., 1989) to assess compulsive behaviors among trauma-exposed populations and those with PTSD (Tuerk et al., 2009). This could be accomplished with procedures akin to those employed to develop the Yale Global Tic Severity Scale (Leckman et al., 1989).

Although beyond the scope of this review, there is also evidence to suggest that trauma is associated with several obsessive-compulsive and related disorders (OCRDs) other than OCD (Forte et al., 2021). This field of study is in its infancy and may benefit from the creation of tools akin to the OTTI or P-TOCS or from adaptations to existing measures of OCRDs to probe associations between OCRD symptoms and trauma.

Supplemental Material

sj-docx-1-asm-10.1177_10731911231208403 – Supplemental material for Assessment of Comorbid Obsessive-Compulsive Disorder and Posttraumatic Stress Disorder

Supplemental material, sj-docx-1-asm-10.1177_10731911231208403 for Assessment of Comorbid Obsessive-Compulsive Disorder and Posttraumatic Stress Disorder by Emily E. Fenlon, Caitlin M. Pinciotti, Alyssa C. Jones, Colton S. Rippey, Hannah Wild, Troy J. J. Hubert, Jordyn M. Tipsword, Christal L. Badour and Thomas G. Adams in Assessment