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Abstract

Objective: To investigate the patterns and predictors of substance use disorders (SUD) and daily tobacco use in first-episode psychosis (FEP).

Method: In this study, consecutive admissions of 126 patients with an initial presentation for FEP were recruited from three psychiatric services. Each patient was assessed with a comprehensive assessment package in order to collect demographic information, to diagnose psychotic disorders and SUD, to estimate the duration of untreated psychosis and to assess premorbid functioning and the severity of psychiatric symptoms.

Results: The rates of lifetime SUD and daily tobacco use were 71% and 77%, respectively. The onset of SUD pre-dated the onset of positive psychotic symptoms in 91% of relevant cases. In multivariate analyses, male gender, younger age, Australian birth and unemployed status were the most consistent demographic predictors of SUD and daily tobacco use. There were no associations found between SUD and symptom severity, premorbid adjustment, psychotic disorder diagnosis or hospitalization.

Conclusions: Male gender and younger age are reliable predictors of SUD in FEP. Patients with and without SUD appear to have similar clinical characteristics at initial presentation.

Keywords

first-episode psychosis schizophrenia substance abuse tobacco use

The investigation of patterns and predictors of substance use disorders (SUD) in psychotic disorders can improve our understanding of the aetiology and consequences of the high rate of comorbid SUD and psychosis [1]. Moreover, the study of SUD in first-episode psychosis (FEP) has the potential to minimize selection and retrospective biases [2] and can inform early identification and treatment of these co-occurring disorders [3]. Previous FEP studies have found that: (i) there is considerable variability in the reported rates of lifetime SUDbetween different localities, ranging from 10% in Singapore [4] to 47% in the US [5]; (ii) the onset of SUD pre-dates the onset of positive psychotic symptoms in the majority of FEP cases [5–7]; (iii) male gender and younger age are frequently associated with SUD [5], [6], [8], [9]; and (iv) there is a lack of consistent association between the severity of general, positive or negative symptoms at initial presentation and SUD [5], [7], [9].

The aim of the present study was to examine the pattern, and predictors of SUD in individuals with FEP. The specific hypotheses were as follows:

1 Initiation of SUD will precede the onset of positive psychotic symptoms in the majority of relevant cases.

2 Male gender and younger age will be associated with SUD.

3 There will be no association between the severity of positive, negative or general symptoms at initial presentation and SUD.

Method

Sample

In this study, consecutive inpatient and outpatient admissions of individuals with FEP were screened between March and July 2001 at the Early Psychosis Prevention and Intervention Centre (EPPIC) and between January and December 1997 at the Central East Area Mental Health Service (CEAMHS) and the Northern Area Mental Health Service (NAMHS). The inclusion criteria were 15–30 years old, fluency in English, ability to give informed consent and clear evidence of psychosis. The exclusion criteria were organic aetiology, intellectual impairment, history of brain damage or epilepsy and more than 6months of prior treatment for psychosis. All participants provided written informed consent. The research and ethics committees of the North Western Mental Health Program approved the study.

The sample comprised 126 participants who met the study criteria (EPPIC, n=71; CEAMHS, n=32; NAMHS, n=23). Information on non-participants was available at EPPIC: 112 patients were admitted during the recruitment period; however, 15 patients did not meet the criteria, 15 patients declined participation and 11 patients could not be recontacted to complete the diagnostic assessment. Diagnostic and other clinical information was collected for eligible non-participants (n=26) by way of an initial interview with the patient (in 73.1% of cases), informant interviews with a family member and/or the treating medical officer and a file review.

Measures

Participants underwent a comprehensive diagnostic assessment using the Royal Park Multidiagnostic Instrument for Psychoses (RPMIP) [10]. The RPMIP is a semistructured interview used to diagnose DSM-IV psychotic disorders and to estimate the duration of untreated psychosis (DUP) in days, defined as the time from onset of psychotic symptoms to service entry.

Lifetime and 12-month SUD (abuse or dependence) before treatment entry were assessed using the Chemical Use, Abuse and Dependence Scale (CUAD) [11]. The CUAD is a brief semistructured interview used to diagnose SUD according to DSM-III-R criteria and includes an assessment of maximum frequency, amount, mode and duration of SUD. The presence and duration of lifetime and 12-month daily use of tobacco (minimum duration of 1 month) was also recorded. ‘Other SUD’ was defined as any SUD other than alcohol or cannabis and ‘poly SUD’ was defined as the presence of at least two of alcohol, cannabis or other SUD [12].

The Premorbid Adjustment Scale (PAS) [13], the Brief Psychiatric Rating Scale (BPRS) [14] and the Scale for the Assessment of Negative Symptoms (SANS) [15] were administered at baseline. All sources of available information (patient and informant interviews and review of medical records) were used to make diagnostic and clinical ratings.

Predictors of substance use disorders

Candidate predictors of SUD included gender, age (15–19, 20–24 or 25–30 years old), marital status (married/de facto or single), country of birth (Australia or overseas), employment status (employed/ student/home duties or unemployed), education (incomplete secondary school, or completed secondary school or equivalent), age at psychosis onset (18 years old or younger, or at least 19 years old), BPRS total score, BPRS psychotic subscale score, SANS total score, psychotic disorder diagnosis (non-affective psychosis [schizophrenia, schizophreniform and delusional], affective psychosis [schizoaffective, bipolar and major depression], or other psychosis [psychosis not otherwise specified, brief and substance-induced]), DUP (logtransformed because of positive skewness), PAS Early Adolescence subscale and inpatient or community-based treatment.

Data analyses

Descriptive statistics for demographic, clinical and substance use variables were computed. Exact tests were used to test for associations between substance use variables. Construction of multivariate binary logistic regression models involved two steps. First, univariate associations between independent and dependent variables were identified at a significance level at or less than 0.05 probability using logistic regression analysis. Second, gender and age, as well as other candidate predictors associated with the dependent variable in univariate analyses at a significance level less than 0.10 probability, were entered in a single step into a series of multivariate models. Predictors were regarded as useful to a multivariate model if the significance level of the Wald test was at or less than 0.05 probability. Statistical analyses were undertaken using SPSS for Windows (V 12.0.1).

Results

Sample

The sample comprised 89 men (70.6%) and 37 women (29.4%) and the mean age was 21.5 years (SD=3.5 years). Psychotic disorder diagnostic categories were as follows: non-affective psychosis, 64.3%; affective psychosis, 28.6%; other psychosis, 7.1%. A multivariate model tested for differences between participants and eligible non-participants at EPPIC on demographic variables, psychotic disorder diagnosis, DUP and hospitalization. The results indicated that DUP was the only significant predictor (p=0.04); there was a longer DUP (median, mean and SD) for non-participants (90.0, 302.7 and 467.9) compared to participants (28.0, 123.0 and 257.4).

Rates of lifetime and 12-month substance use disorders and daily tobacco use

The rates of lifetime and 12-month SUD and daily tobacco use are presented in Table 1. The rates of any lifetime SUD and lifetime daily tobacco usewere 71.4% and 77.0%, respectively. There were no patients identified with cocaine or phencyclidine use disorders.

Table 1.

Rates of lifetime and 12-month substance use disorders (SUD) and daily tobacco use (n=126)

Characteristics of lifetime substance use disorders and daily tobacco use

Details of the characteristics of lifetime SUD and daily tobacco use are presented in Table 2. The mean duration of daily tobacco use was longer than the mean duration of cannabis use disorder, and the mean duration of cannabis use disorder was longer than the mean duration of both alcohol and other SUD. The onset of any SUD pre-dated the onset of positive psychotic symptoms by at least 12 months in 91.1% of relevant cases.

Table 2.

Maximum frequency, main route of use, duration and prior onset of substance use disorders (SUD) and daily tobacco use (n=126)

Associations among different types of lifetime substance use disorders and daily tobacco use

The associations between different types of lifetime SUD and daily tobacco use are presented in Table 3. There were significant associations between alcohol use disorder and cannabis use disorder (exact p=0.002) and daily tobacco use (exact p=0.02), cannabis use disorder and other SUD (exact p=0.005) and daily tobacco use (exact p<0.001), and other SUD and daily tobacco use (exact p<0.001). The association between alcohol and other SUD was not statistically significant (exact p=0.39). There were significant associations between poly SUD and alcohol use disorder (exact p<0.001), cannabis use disorder (exact p<0.001), other SUD (exact p<0.001) and daily tobacco use (exact p<0.001). Approximately four in every 10 patients with cannabis use disorder also had either alcohol or other SUD, whereas more than eight in every 10 patients with alcohol or other SUD also had cannabis use disorder. Accordingly, there were proportionately fewer patients with cannabis use disorder who engaged in poly SUD. Furthermore, eight in every 10 patients with daily tobacco use met criteria for cannabis use disorder.

Table 3.

Patterns of lifetime substance use disorders (SUD) and daily tobacco use (n=126)

Demographic and clinical correlates of lifetime substance use disorders and daily tobacco use

Significant associations were identified in univariate analyses between male gender and cannabis use disorder (OR=3.4, 95% CI=1.5–7.5, p=0.003) and daily tobacco use (OR=2.5, 95% CI=1.0–5.9, p=0.04); younger age and other SUD (20–24 years old vs 25–30 years old, OR=4.9, 95% CI=1.3–18.2, p=0.02), poly SUD (15–19 years old vs 25–30 years old, OR=6.4, 95% CI=1.9–21.8, p=0.003; 20–24 years old vs 25–30 years old, OR=4.6, 95% CI=1.4–15.1, p=0.01) and daily tobacco use (20–24 years old vs 25–30 years old, OR=4.1, 95% CI=1.4–11.7, p=0.009); Australian birth and cannabis use disorder (OR=5.8, 95% CI=2.3–14.8, p<0.001) and poly SUD (OR=3.9, 95% CI=1.4–11.1, p=0.01); incomplete secondary education and daily tobacco use (OR=3.2, 95% CI=1.3–7.4, p=0.008); unemployed status and other SUD (OR=6.0, 95%CI=2.4–15.4, p<0.001), poly SUD (OR=2.5, 95% CI=1.0–6.1, p<0.05) and daily tobacco use (OR=9.2, 95% CI=1.2–71.3, p=0.03); and psychotic disorder diagnosis (non-affective vs affective) and alcohol use disorder (OR=4.2, 95% CI=1.4–13.2, p=0.01) and daily tobacco use (OR=2.7, 95% CI=1.1–6.6, p=0.03).

The majority of significant associations identified in univariate analyses remained significant in multivariate analyses (Table 4). However, the associations between psychotic disorder diagnosis and alcohol use disorder as well as daily tobacco use were no longer significant. Furthermore, a significant association emerged between younger age (20–24 years old vs 25–30 years old) and cannabis use disorder. The wide confidence interval estimate for employment status as a predictor of daily tobacco use was because only one out of 25 unemployed patients did not meet criteria for daily tobacco use.

Table 4.

Multivariate correlates of lifetime alcohol use disorder, cannabis use disorder, other substance use disorders (SUD), poly SUD and daily tobacco use (n=126)

Discussion

Rates of substance use disorders and daily tobacco use

This study found that 71% of patients met criteria for lifetime SUD. The higher rate compared to other FEP studies may be due to one or more of the following factors. First, the patient sample is relatively young and predominantly male, and both younger age and male gender are known risk factors for SUD in patients with psychotic disorders. Second, it seems likely that crossnational differences in prevalence rates of SUD in the community will to some extent be reflected in individuals with psychotic disorders. The prevalence of SUD in the Australian community is probably comparable to the US [16], which is higher than a number of other countries. Third, the use of different diagnostic methods can affect the detection rate of SUD [17]. Reassuringly, an independent study at EPPIC found a similar rate (72%) of lifetime SUD and a high rate (58%) of lifetime cannabis use disorder in FEP [18].

The finding that three in every four patients were daily cigarette smokers is a higher rate of regular tobacco use than previously reported in FEP [5], and suggests that regular tobacco use is a significant physical health issue that is particularly relevant to younger individuals with FEP.

Patterns of lifetime substance use disorders and daily tobacco use

The findings that cannabis and alcohol were the most common SUD, and that a substantial proportion of individuals engaged in poly SUD, are consistent with previous FEP studies [5], [19]. There was evidence for an apparent ‘stepping-stone’ progression from misuse of one substance to another. First, group results indicated that the initiation of daily tobacco use preceded the initiation of cannabis use disorder, which in turn preceded the initiation of alcohol or other SUD. Second, the pattern of associations between daily tobacco use and cannabis, alcohol and other SUD, are broadly consistent with a pathway of stepping-stones from daily tobacco use to cannabis use disorder to alcohol or other SUD. However, whether this pathway is because of the presence of ‘gateway’ effects or simply reflects the typical order in which opportunities to engage in substance use arise in young people is unclear [20].

Temporal order of substance use disorders and positive psychotic symptoms

The findings supported the hypothesis that initiation of SUD would precede the onset of positive psychotic symptoms in most relevant cases and is consistent with previous FEP studies [5], [6]. Of course, the common occurrence of this temporal sequence of onset does not confirm SUD as an aetiological agent [21]. Nevertheless, it does indicate that the role of SUD in the onset of psychosis is likely to be an issue that will need to be addressed with many patients and carers during treatment.

Predictors of substance use disorders and daily tobacco use

The hypothesis that SUD would be associated with male gender and younger age was confirmed. Men were at greater risk for the most common SUD of cannabis. The lack of a gender difference in the risk for alcohol or otherSUDis consistent with recent evidence that younger women are increasingly at greater risk for SUD [22]. Despite the restricted age range of the sample, younger patients were at increased risk for all forms of SUD except alcohol. The finding that patients born in Australia were more likely to develop cannabis or poly SUD is similar to the results from population-based studies [16] and suggests that individual, cultural or selection factors associated with migration afford a degree of protection against the development of SUD. The finding that unemployed patients had a higher risk for other SUD (as well as poly SUD) suggests either that abuse of substances such as stimulants and heroin is a barrier to vocational involvement, or unemployment contributes to the abuse of these substances, or both.

There were no associations found between SUD or daily tobacco use and a range of clinical variables. The hypothesis of a lack of association between severity of positive, negative, or general symptoms at initial presentation and SUD was confirmed by the results and is consistent with other FEP studies [7], [9]. In addition, premorbid adjustment, psychotic disorder diagnosis and hospitalization were not reliably associated with SUD. The lack of predictive utility of premorbid adjustment in this study and other FEP studies [5], [7], [19] casts some doubt on explanatory models that have linked better premorbid adjustment and SUD in individuals with psychosis [23].

The findings that male gender, younger age, incomplete secondary school and unemployment were independent risk factors for regular tobacco use are similar to population-based data [24]. The implication for treatment is that young men with FEP who are at particular social disadvantage aremost likely to be in need of interventions to address health risks associated with smoking.

Strengths and limitations of the study

The strengths of the current study include the recruitment of a representative sample of patientswith FEP from three psychiatric services, the comprehensive diagnostic and clinical assessment based on multiple information sources and the use of multivariate analyses to identify independent predictors of SUD. The main limitation of the study is the relatively small sample size that may have impeded the detection of important associations between variables due to of lack of statistical power.

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Patterns and Predictors of Substance use Disorders and Daily Tobacco use in First-Episode Psychosis

Abstract

Keywords

Method

Sample

Measures

Predictors of substance use disorders

Data analyses

Results

Sample

Rates of lifetime and 12-month substance use disorders and daily tobacco use

Characteristics of lifetime substance use disorders and daily tobacco use

Associations among different types of lifetime substance use disorders and daily tobacco use

Demographic and clinical correlates of lifetime substance use disorders and daily tobacco use

Discussion

Rates of substance use disorders and daily tobacco use

Patterns of lifetime substance use disorders and daily tobacco use

Temporal order of substance use disorders and positive psychotic symptoms

Predictors of substance use disorders and daily tobacco use

Strengths and limitations of the study

References