A 12-month prospective follow-up study of patients with schizophrenia-spectrum disorders and substance abuse: changes in psychiatric symptoms and substance use

While it is widely known that patients with schizophrenia-spectrum psychoses and co-occurring substance use disorders are more difficult to manage, there is limited data on the course of their psychiatric symptoms when they remain in treatment over time. This prospective 12-month study evaluated changes in psychiatric symptoms and substance use to ascertain if the co-existence of substance use disorders influences ratings of psychiatric symptoms at follow-up. 147 outpatients in a continuing care program were assessed at intake and followed prospectively for 12 months. Psychiatric symptoms were measured at baseline and 12-month follow-up using the Positive and Negative Syndrome Scale (PANSS) and Hamilton Depression Rating Scale (HAM-D). Subjective psychological distress was rated with the Brief Symptom Inventory (BSI) and quality of life by the Satisfaction with Life Domains Scale (SDLS). Drug and alcohol use was measured with the Addiction Severity Index (ASI). 50.3% of patients were diagnosed with dual disorders (DD) (current and lifetime). The most common primary substances of abuse were alcohol (35.6%) and cannabis (35.1%). DD subjects had higher baseline PANSS positive scores but experienced a greater reduction at 12 months compared to single diagnosis (SD) patients. Severity of substance abuse as measured by ASI composite scores did not decrease significantly between baseline and 12 months. DD patients with schizophrenia and related psychoses treated for their psychiatric illness showed a reduction in PANSS scores over 12 months, even when their substance use remained largely unchanged. However, co-morbidity cases continued to show higher depression and anxiety ratings. Ongoing substance abuse appears to be related to levels of depression as 62.5% of DD-current versus 34.7% of SD patients had HAM-D scores in the depressed range at 12-month follow-up. Implications for treatment are discussed.