Comorbidity of substance use disorders in schizophrenia, schizoaffective and bipolar disorders

Epidemiological studies such as the Epidemiological Catchment Area survey (18) have shown that bipolar or schizophrenic patients are especially prone to display a comorbid substance use disorder. These studies have demonstrated that this comorbidity condition constitutes a major mental health problem owing to its high frequency. The aim of the present study was to assess the prevalence of a comorbid substance use disorder in a sample of psychotic patients, and to compare the pattern of street drug use in schizophrenic, schizoaffective and bipolar patients. Comorbidity of illicit substance use disorders was assessed with the Composite International Diagnostic interview in 92 consecutive patients fulfilling the DSM III-R criteria for bipolar disorder (SA, n = 40), schizophrenia (S, n = 38) and schizoaffective disorder (SA, n = 14). The lifetime prevalence for any substance use was 25 % in the fetal sample, and did not differ significantly between the three groups, although a higher prevalence was found in SA (BP : 20 %, S : 23, 7 %, SA : 42,9 %, NS). The current prevalence (previous six months) was 14, 1 %, in the total sample (BP : 17,5 %, S: 7,9 %, SA :21,4 %, NS). In the three diagnostic groups, the most commonly used drug was cannabis, followed by opiates and cocaine. These results do not confirm that schizophrenics might preferentially display abuse or dependence on psychostimulants, and highlight the possible role for the drug choice of the availability of the various illicit drugs in the geographical environment of the subject. Nearly half patients (47,8 %) have a lifetime history of abuse or dependence on at least two different drugs. Age at onset of substance use disorder was earlier than or concomitant to that of schizophrenic and/or mood symptoms in most patients. This chronological pattern was the same in the three diagnostic groups. Clinical variables (age at onset, age at first hospitalization, number of hospitalizations) and sociodemographic variables (age, sex, educational level, marital and occupational status) did not significantly differ between patients with a lifetime history of drug abuse or dependence and those without. Patients presenting with a current abuse or dependence were younger than those without. These results confirm in a French sample of schizophrenic and/or mood disordered patients the high frequency of the comorbidity with substance use disorders.