Cannabis using schizophrenia patients treated with atypical neuroleptics: do their symptoms differ from those of cannabis abstainers?

Several studies have found that symptom patterns of cannabis-using schizophrenia patients differ from those of nonusers. However, these investigations have mostly included patients treated with typical neuroleptics (TN). Since differing symptoms could also result from a TN-cannabis combination and might not be due to cannabis use per se, this study examined schizophrenia symptoms in a group of cannabis-using outpatients treated with atypical antipsychotics. Forty-two schizophrenia outpatients participated and were divided into three groups: cannabis abstainers, moderate users, and daily users. Patients with any substance use disorder other than cannabis abuse/dependence, or patients meeting criteria for schizotypal, schizoaffective, affective, anxiety, delusional, or personality disorders were excluded from the study. All patients completed a self-constructed questionnaire assessing demographic and drug use characteristics and were interviewed using the semistandardized Positive and Negative Syndrome Scale (PANSS). Cannabis use was assessed by self-declaration. No differences were found between the abstainers, the moderate, and the daily users on the PANSS scores. Thus, schizophrenia patients treated with atypical neuroleptics do not differ in symptom patterns whether using or not using cannabis. The study's limitations are noted.