Discontinuing cannabis use: Symptomatic and functional outcomes in people with an established psychotic disorder

For people with psychotic disorders, the negative outcomes associated with continuing cannabis use would suggest that discontinuing such use may be beneficial for their symptomatic and functional recovery. However, existing evidence that discontinuation is associated with better clinical outcomes is inconsistent and it remains unclear whether discontinuing use is associated with improvements in outcomes for people with an established psychotic disorder. In this 3-5-year longitudinal study we examined baseline and follow-up symptomatic and functional profiles of 371 people with an established psychotic disorder, comparing those who continued to use cannabis with those who discontinued use after baseline assessment. At follow-up, one third (33.3 %) of baseline cannabis users had discontinued use. Discontinuation was associated with significantly lower odds of past-year hallucinations and a mean improvement in level of functioning (Personal and Social Performance Scale) compared to a decline in functioning in continuing users. No significant differences in severity of negative symptoms were observed. With few longitudinal studies examining symptomatic and functional outcomes for people with established psychotic disorders who continue to use cannabis compared to those who discontinue use, our findings that discontinuing cannabis was associated with significant clinical improvements fill gaps in the evidence-base.