Effects of persistent cannabis use on depression, psychosis, and suicidality following cannabis-induced psychosis: A longitudinal study.

Abstract

Background and objectives: Cannabis use is associated with psychotic disorder onset and exacerbation. This study examines how continued cannabis use affects depressive symptoms, psychotic symptoms, and suicidal behaviors following cannabis-induced first-episode psychosis (FEP).

Methods: Sixty-five participants (aged 16-50 years) with FEP were recruited from psychiatric inpatient facilities in northern Italy. Participants were categorized into two groups: non-cannabis users (NCU) and cannabis users (CU), based on substance use during the 9-month follow-up. Twenty-one participants (32.3%) were lost to follow-up, with a final sample of 44 subjects (NCU = 22, CU = 22). Assessments were conducted at baseline, 3 months, and 9 months using PANSS, CDSS, SSI, and GAF scales).

Results: CU exhibited persistently higher depression (CDSS) and suicidality (SSI) scores than NCU throughout follow-up, with significant differences at both 3 months (CDSS: p = .000006; SSI: p < .001) and 9 months (CDSS: p = .0000001; SSI: p < .001). Positive psychotic symptoms improved in both groups, though CU showed slower recovery and higher relapse rates (59.9% vs. 18.8%). PANSS positive subscale scores remained significantly higher in CU at 3 months (p = .001) and 9 months (p < .0002). GAF scores improved significantly only in NCU (p = .024 at 9 months).

Discussion and conclusions: Continued cannabis use adversely affects depressive and psychotic symptoms and suicidality in FEP patients, while cannabis cessation is associated with improved clinical outcomes.

Scientific significance: This study tracks depressive symptoms, suicidality, and psychotic manifestations in cannabis-induced FEP, demonstrating that continued use is associated with treatment-resistant depressive symptoms even when psychotic symptoms improve, highlighting the need for integrated clinical approaches.