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Abstract

Objective: Attention deficit hyperactivity disorder, combined type (ADHD-CT), dysthymic disorder, and anxiety disorders frequently co-occur in primary school age children, although there have been no published data describing their association. We investigated the association of anxiety, defined from a parent or child perspective, with primary school-age children with ADHD-CT with and without dysthymic disorder.

Method: One hundred and forty-six medication naïve children with ADHD-CT were studied. Two groups with and without dysthymic disorder were formed to compare parent and child reports of anxiety, using categorical and continuous measures of anxiety, using logistic regression.

Results: Separation anxiety disorder and social phobia were associated with primary school-age children with ADHD-CT and dysthymic disorder, compared to children with ADHD-CT without dysthymic disorder.

Conclusions: The recognition of dysthymic disorder and anxiety disorders and their management in primary school-age children with ADHD-CT is generally poorly understood. The identification and elucidation of composite anxiety and depressive phenomena that may be systematically investigated through longitudinal studies of epidemiologically derived samples is needed in this particular group of children.

Keywords

ADHD-CT anxiety dysthymic disorder

The greater–than–chance association of attention deficit hyperactivity disorder, combined type (ADHDCT) and dysthymic disorder (DD) has been demonstrated in epidemiological and clinical samples [1–5]. Prevalence rates of 15–30% have been reported for primary school-age children with ADHD-CT and DD (DSM-III/III-R equivalent diagnostic constructs) [1, 5] and between 20–30% for primary school-age children with DD and ADHD-CT (DSM-III equivalent diagnostic constructs) [4].

Attention deficit hyperactivity disorder, combined type and DD are important to systematically study because they are common in primary school age children, frequently chronic [6], and may confer an increased risk of completed suicide in adolescence. Dysthymic disorder has an earlier age of onset than major depressive disorder and frequently precedes the onset of major depressive disorder in adolescence [2, 4, 6]. Increased rates of alcohol and substance abuse/dependence disorders and conduct problems are associated with major depressive disorder, and independently ADHDCT in adolescence [7, 8], and these three factors are associated with an increased risk of completed suicide [9]. In addition, ADHD-CT and DD has been associated with treatment non-responsiveness when the ADHD-CT symptoms alone are the target of psychostimulant medication and/or psychological treatment [10, 11].

The further co-occurrence of anxiety is essential to consider given recent evidence that self-reported anxiety and depressive symptoms in children and adolescents are associated with shared genetic factors that implicate a common set of biological mechanisms that confer a vulnerability to these symptoms along with developmental phase-specific environmental factors [12, 13]. In addition, anxiety disorders have an age of onset in middle and late childhood [14, 15], as does DD [4, 6]. Attention deficit hyperactivity disorder, combined type also has its peak prevalence in these developmental periods [1]. Further, the recent MTA study [16] reported a lower dose of psychostimulant medication use in the group of children with ADHD-CT and anxiety who received combined psychostimulant medication and behavioural treatment compared to psychostimulant medication alone, which is consistent with prior reports of a differing treatment responsiveness in this subgroup [17]. Neuropsychological and neurophysiological markers have been associated with this poorly responding ADHD-CT and anxiety group [18–20]. These include a decreased ability to perform a serial addition digit span task [18], and an increased sensitivity to augmented noradrenergic function [19, 20]. To date no published data describes the association of anxiety with ADHD-CT with and without DD.

Parent and teacher perspectives have been used to define ADHD-CT [21], while parent- with or without child-reported features of DD have been used to maximize the homogeneity of the samples studied [4, 6]. In contrast, the child report, in addition to the parent report, of anxiety disorders, is important because of its known usefulness in identifying internalizing symptoms [21–23] and the known low rates of agreement between parent and child reports of anxiety disorders [21, 24]. March et al. [25] have reported that the parent report of anxiety may be a reflection of the ‘negative affectivity associated with a child's behavioural problems’, rather than ‘neurotic’ anxiety found in children with anxiety disorders. The variation of ADHD-CT, DD and anxiety symptoms in different situations also necessitates the collection of parent, teacher, and child self-reports of symptoms being present or absent, and the use of categorical and continuous variables to define the ‘presence’ or ‘absence’ of ADHD-CT, DD and of anxiety [3, 25, 26].

This study investigated a group of primary school age children with ADHD-CT [1] with and [2] without DD. Parent- and child-reported anxiety disorders were defined from a categorical and dimensional perspective and their associations with the two groups above described.

Method

Subjects

One hundred and forty-nine children aged from 6 to 12 years were identified in a specialized clinic for ADHD in the southern region of metropolitan Melbourne, Australia. All the children had ADHD-CT (DSM-IV criteria), defined through a semistructured clinical interview with the child's parent(s) and by the parent- and/or teacher-report of the subscale scores of the core symptom domains of ADHD-CT being greater than 1.5 standard deviations above the mean for a given child's age and gender. The children were all psychostimulant medicationnaïve and were consecutively referred for assessment because they were not responding to usual clinical psychological management approaches. The children met the inclusion criteria of living in a family home (and not in an institution) and attending normal primary schools. All had intelligence quotients above 70 and none had overt neurological disease or psychotic symptoms. There was no refusal and parent(s) gave informed consent. Ethics committee approval was obtained for the study. Two groups were formed based on the presence/absence of DD, defined using a semistructured clinical interview with the child's parent(s) alone, given the low numbers of combined parent- and child-reported and child-only-reported DD, the clarity of using a single informant perspective given potential low parent: child concordance [21] and the consistency with the diagnosis of ADHD-CT being based on the parent-only report [21]. Thirty-nine children received a diagnosis of DD: parent-only-reported DD (n = 29); parent- and child-reported DD (n = 3); child-only-reported DD (n = 7); and no DD (n = 107). Six children received an additional diagnosis of major depressive disorder, although none of these children had current symptoms consistent with MDD at the time of assessment. Three children received a diagnosis of major depressive disorder alone and were excluded from the sample studied (n = 146). Anxiety disorder diagnoses were defined from a parent and a child perspective using a semistructured clinical interview. The ADHD-CT with and without DD groups were compared for age, gender, ADHD-CT symptoms, Verbal/Performance/Full Scale IQ, language-based learning abilities (spelling and reading), general family functioning, social adversity factors, and oppositional defiant disorder (ODD)/conduct disorder (CD), given that these diagnoses have an independent association with ADHD-CT, anxiety and dysthymic disorders. These variables did not significantly differ between the groups. Subject characteristics were compared across the two groups using independent t-tests (Table 1).

Table 1.

Subject characteristics

Measures

Child Behaviour Checklist (CBCL) [27] consists of 118 behaviour problem items, which are rated by the parent and teacher on a 3-point scale as to how well each describes the child. Parent- and teacher-forms are completed. A total behaviour problems scaled score, including subscale scores of all the symptom domains of ADHD-CT, and an anxiety/ depression subscale, were generated. All scores form continuous variables. The CBCL is well researched and has adequate psychometric properties.

Anxiety Disorders Interview Schedule for Children (A-DISC) [28] is a semistructured diagnostic interview schedule based on DSM-IV criteria with child and parent versions. It is frequently used internationally by researchers to diagnose childhood anxiety disorders and a range of other disorders, including ADHD-CT, ODD/CD and DD based on the DSM-IV criteria. It yields a categorical variable of the presence or absence of a given disorder. Research findings support the clinical utility, reliability and validity of the A-DISC.

Revised Child Manifest Anxiety Scale (R-CMAS) [29] consists of 37 items designed to assess anxiety. The R-CMAS also contains a scale to assess social desirability. All scores form continuous variables. Good test-retest reliability and concurrent validity have been demonstrated.

Parental Account of Childhood Symptoms (PACS) [30] is a semistructured clinical interview developed as an instrument for the measurement of children's behaviour problems as experienced at home. It is administered by a trained interviewer. Parents are asked for detailed descriptions of what their child has done in specified situations over the previous week and over the preceding 12 month period. In all, 44 items of behaviour are enquired about in this way. Three subscales are generated as continuous variables: hyperactivity, emotional disorder and defiance. It also yields demographic data. A social adversity scale (range 3-) is formed from the summary of family income level (1–2), mother's educational level (1–2), single parent status (0–1), sibling size (0-), and broken home status (1–2). It has adequate validity and reliability and has been used extensively in published research studies.

Family Assessment Device (FAD) [31] was developed from the McMaster Model of Family Functioning to measure the structural and organizational characteristics of families. It consists of 60 items that measure six dimensions of family functioning: problem solving; communication; affective responsiveness; affective involvement; roles; and behavioural control. Each dimension forms a subscale with an additional general functioning subscale that measures the overall health/dysfunction in the family unit. Adequate validity and reliability have been demonstrated in published research findings.

The third edition of the Wechsler Intelligence Scale for Children (WISC-3) [32] was used. This provides verbal, performance and fullscale scores of measured intelligence. The third edition of the Wide Range Achievement Test (WRAT-3) [33] provides a measure of spelling and arithmetic abilities. Both of the above tests are well established with Australian normative data.

Procedure

The Child Behaviour Checklist (CBCL) [27] parent-forms were completed prior to the child's assessment. The child was initially interviewed by a Fellow in Child and Adolescent Psychiatry who completed the Anxiety Disorders Interview Schedule for Children (A-DISC) [28] child-form. The child subsequently completed the Revised Child Manifest Anxiety Scale (R-CMAS) [29]. At a separate interview, a registered psychologist administered the WISC-3 [32] and the WRAT-3 [33] to the child, while a Fellow in Child and Adolescent Psychiatry concurrently administered the Anxiety Disorders Interview Schedule for Children (A-DISC) [28] parent-form and the parents completed the Parental Account of Childhood Symptoms (PACS) [30] and the Family Assessment Device (FAD) [31].

Variable definition and data analysis

Two groups were formed from using a semistructured clinical interview. The parent-only report of DD was correlated (product-moment correlations) with the respective continuous variable of anxiety/depression from the parent report (CBCL-anxiety/depression subscale Tscore: 67.72 11.[84]) and the teacher report (TRF-anxiety/depression subscale T-score: 60.21 8.[53]) to ensure that this categorical variable was an adequate measure of dysthymia. Separate categorical variables were formed from the parent- and child-reports of comorbid anxiety diagnoses, using a semistructured clinical interview. Each had a value of ‘1’ if one or more anxiety disorder(s) was/were present or ‘0’ if not present, from the respective parent- and child-reports, and each was correlated (product-moment correlations) with the respective continuous variable of anxiety/depression from the parent report (CBCLanxiety/ depression subscale T-score: 67.72 11.[84]) or anxiety from the child's self-report (RCMAS-total anxiety T-score: 52.21 11.[53]) to ensure the categorical variables were an adequate measure of anxiety, from the parent and the child perspectives. The χ² test was used to compare these two categories of anxiety in the sample of 136 children. The parent and child reports of comorbid anxiety were described by their total number, the percentage of each diagnosis and the number of children with one or more anxiety disorder diagnoses within the two groups of ADHD-CT with and without DD. Separate univariate logistic regression analyses were then performed, to determine which anxiety disorder variables predicted group membership of the ADHD-CT and DD group. The main advantage of the logistic regression statistical model is its ability to accommodate multiple categorical and continuous independent variables as predictors without an increase in the number of degrees of freedom [34].

Results

The prevalence of DD in this sample of children with ADHD-CT ranged from 2% (parent- and child-reported DD) through 5% (child-only-reported DD), 20% (parent-only-reported DD), and 27% (combined parent- and child-reported DD). The prevalence of major depressive disorder was 6% and ‘double depression’ [35] 4%.

The ADHD-CT and DD group had a significant but small strength correlation with the anxiety/depression subscale score from the parent report (r = 0.25, p < 0.01) and a non-significant correlation with the anxiety/depression subscale score from the teacher report (r = 0.14, p = 0.14).

The presence of one or more anxiety disorders from the child's perspective had a medium strength correlation with the total anxiety score from the child's self-report of anxiety (r = 0.35; p < 0.001). The presence of one or more anxiety disorders from the parent's perspective had a small strength correlation with the anxiety/depression subscale score from the parent report (r = 0.24; p < 0.05). There was a non-significant association of the parent and child reports of the presence of one or more anxiety disorders (χ² (1) = 0.47, p = 0.50).

Table 2 outlines the number and percentage of the parent and child reported anxiety disorders in the ADHD-CT with and without DD groups and Table 3 records the separate univariate logistic regression analyses for the anxiety disorder diagnoses. The parent-report of one or more anxiety disorders was significantly increased in the ADHD-CT and DD group ((χ² (1) = 6.15, p = 0.01), while the child report of one or more anxiety disorders was not ((χ² (1) = 0.14, p = 0.71). Parentreported separation anxiety disorder and social phobia predicted ADHD-CT and DD group membership.

Table 2.

Co-occurring anxiety disorder diagnoses in the ADHD-CT and parent-only dysthymic disorder and no dysthymic disorder groups

Table 3.

Univariate results for separate logistic regressions predicting ADHD with or without dysthymic disorder group membership from the parent- and child-reported anxiety disorders^†

Discussion

The prevalence rates of DD and major depressive disorder in this sample of primary school-age children with ADHD-CT were consistent with those for more generally defined ‘depressive disorders’ (DSM-III/ DSM-III-R criteria) [1, 35, 36]. However, they were considerably lower than those for major depressive disorder reported by Biederman et al. [37] (29%) and Willicutt et al. [38] (22%), although the latter sample included adolescents up to the age of 18 years. In contrast, the prevalence rates for oppositional defiant disorder and conduct disorder were similar across all of the above studies. Careful selection of community and/or clinical samples and clear documentation of their referral pathways into research studies are needed. Also, categorical and dimensional definition of specific depressive disorders are required.

There was an adequate correlation of parent-onlyreported DD with the anxiety/depression subscale score from the parent-report (CBCL) although a non-significant correlation with the anxiety/depression subscale score from the teacher report (TRF). This is not surprising given the broad nature of these subscale measures, which includes essential symptom characteristics of DD, the importance of the home and school contexts in partly determining children's behaviour/mood states, the opportunities of parents and/or teachers to notice particular behaviours/mood states and the context-dependent referents that are used by parents and teachers to grade behaviours/mood states [39–41].

The dimensional measures of anxiety, from parent and child perspectives, were adequately correlated with the categorical anxiety disorder diagnoses, which supported the content validity of these diagnoses. There was no association between the parent and child reports of anxiety, consistent with the previous findings of low agreement between parent and child reports in ADHD-CT [42] and non-ADHD-CT [21–23] samples, and further justification for analysing these reports separately [42].

Table 2 outlines the parent- and child-reported anxiety disorders in the ADHD-CT and DD group compared to the ADHD-CT alone group. There are no equivalent published data to our knowledge. Prevalence rates of anxiety disorders are higher in the ADHD-CT and DD group compared to ADHD-CT alone (DSM-III, DSM-III-R, DSM-IV equivalents) samples [35–38, 42] and depressive disorders alone (dysthymic disorder alone, major depressive disorder alone and combined depressive disorders) (DSM-III, DSM-III-R, DSM-IV equivalents) samples [2, 4, 43]. These lower prevalence rates in ADHD-CT alone and depressive disorders alone samples are evident despite methodological limitations such as the variable definition of ADHD-CT, depressive, and anxiety disorders (DSM-III, DSM-III-R, DSM-IV equivalents), the broad age range of children and adolescents studied, the varying gender composition of the samples studied, marginal differences in child samples, noticeably more girls in adolescent samples, varying sample sizes, and the varying sampling procedures used. These findings are consistent with known greater-than-chance association of ADHD-CT and depressive disorders, including DD, and ADHD-CT and anxiety disorders [44, 45].

The specific association of parent-reported separation anxiety disorder and social phobia with ADHD-CT and DD (Table 3) is explained in part by the known association of ADHD-CT and separation anxiety disorder [46], ADHD-CT and social phobia [47], DD and social phobia [48] and DD and separation anxiety disorder [49], among other anxiety disorders in child and adolescent samples. Further, the age of onset of parent reported separation anxiety disorder, social phobia, ADHD-CT and DD is consistently within the primary school-age period [14, 50, 51], which also supports their association. At a phenomenological level, parent-reported separation anxiety disorder and social phobia may reflect a pervasive vulnerability in children with ADHD-CT and DD, changing from a primary school (perceived low stimulus) to a less sheltered high school (high stimulus) environment. Their behaviour at home suggests separation anxiety while their behaviour at school indicates social phobia, giving rise to these diagnoses. Such a pervasive vulnerability may indicate a genetically based phenotype. However, parentreported separation anxiety disorder is known to be the least stable of the anxiety disorders over time [50] and therefore it is important that the above association is explored using a longitudinal study design of ADHD-CT with and without DD groups. In addition, a larger sample that allows a principal components analysis to further refine a possible genetically based phenotype is required.

Apart from this study's cross-sectional design, a further limitation is the clinic-referred sample investigated. Although the referral pathway into the study is transparent, referral biases into the child mental health service from which the sample was derived are not systematically accounted for [52] and therefore the representativeness of the findings for children with ADHD-CT and DD is a pertinent issue. An epidemiologically derived sample of children with ADHD-CT and DD would address this limitation. Further, a longitudinal study design with an additional DD group and a control group, free from neurological, endocrine and psychiatric disorder, would enable DD-specific factors and general developmental factors of childhood to be controlled. Then the pervasive vulnerability, so defined earlier, may be a suitable phenomenon for future systematic investigation of putative shared genetic factors that implicate a common set of biological mechanisms that confer a vulnerability to this phenomenon along with developmental phase-specific environmental factors [12, 13].

At a clinical level, the recognition of co-occurring DD and associated separation anxiety disorder and social phobia is emphasized by the above findings, for the children with ADHD-CT were referred because they were not responding to conventional individual and group psychological treatments focused on their core ADHD-CT symptoms [52]. If these co-occurring mood and anxiety disorders were noted, more specific medication and psychological treatments targeting all their disabling symptoms could be put in place, along with specific psychological treatments enhancing existing resilience factors for a given child and their unique interpersonal, family, social, cultural and developmental context [53, 54]. Further systematic investigation of the potential synergism between such focused medication and psychological interventions (at individual, parent– child, family and peer group levels) at particular developmental periods within childhood and adolescence, is required [55].

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Which Anxiety Disorders May Differentiate Attention Deficit Hyperactivity Disorder,Combined Type with Dysthymic Disorder from Attention Deficit Hyperactivity Disorder,Combined Type Alone?

Abstract

Keywords

Method

Subjects

Measures

Procedure

Variable definition and data analysis

Results

Discussion

References