OBJECTIVES

To examine the association between clozapine treatment and frequency of cannabis use in adolescents with co-occurring psychotic and cannabis use disorder in a retrospective cohort chart review.

METHOD

We conducted a retrospective cohort chart review of patients diagnosed with a psychotic disorder and concurrent cannabis use disorder admitted to a tertiary care youth inpatient unit from 2010-2012. Longitudinal exposure and outcome data was coded month-by-month. Frequency of cannabis use was measured using a 7-point ordinal scale. Severity of psychosis was measured on a 3-point ordinal scale. Mixed effects regression modeling was used to describe the relationship between exposure and outcome variables.

RESULTS

Thirteen patients had exposure to clozapine and fourteen had no exposure to clozapine. Cannabis use decreased in patients treated with clozapine, compared to patients treated with other antipsychotics (OR 2.8; 95% CI 0.97-7.9). Compared to no medication, clozapine exposure was associated with significantly less cannabis use (OR 7.1; 95% CI 2.3-22.3). Relative to treatment with other antipsychotics, clozapine exposure was significantly associated with lower severity of psychotic symptoms (OR 3.7; 95% CI 1.2-11.8).

CONCLUSIONS

Clozapine may lead to decreased cannabis use and psychotic symptoms in adolescents with concurrent psychosis and substance use. Clinical trials are warranted.