Cannabis Use Among Forensic Mental Health Patients Rose After Canadian Legalization, With Clinical Consequences

One-third of forensic patients used cannabis over the study period, with frequency increasing significantly after legalization. Those who used cannabis were more likely to be readmitted to hospital and had higher static risk factors for violence. Over half experienced mental health worsening within a week of use. However, actual violence rates did not differ between users and non-users.

Pseudo-prospective study of 187 forensic mental health patients in Ontario over four years (two pre- and two post-legalization), tracking cannabis use frequency, clinical outcomes, and safety measures.

Forensic mental health patients represent one of the populations most vulnerable to cannabis-related harms. This study provides direct evidence that legalization increased cannabis use in this population and that use was associated with clinical deterioration, even if not with violence.

This study is among the first to directly examine legalization's impact on forensic psychiatric patients. The dissociation between clinical deterioration and violence is important: cannabis harmed these patients' mental health and recovery without making them more dangerous to others.

Single province (Ontario). Relatively small sample. Cannabis use detected through self-report and urine testing, which may miss some use. Could not control for cannabis potency or product type. Pre-post design limits causal inference.