Medicinal cannabis consistently improved quality of life across chronic conditions, with effects growing larger over time

RCTs showed small but statistically significant short-term HRQL improvements (Cohen's d=0.30, p=0.03). Observational studies showed improvements across all follow-up periods: short-term (d=0.43), medium-term, and long-term (d=0.74), all p<0.001. Only 61% of studies justified why they measured quality of life, and only 8% provided definitions.

Systematic review searching seven databases from January 2015 to April 2025. Sixty-four studies retained: 12 RCTs, 38 cohort studies, 13 case series, 1 non-randomized experimental. Meta-analyses conducted for short-term (2 weeks to 3 months), medium-term (3-12 months), and long-term (12+ months) outcomes. Risk of bias assessed for RCTs.

Quality of life is ultimately what matters most to patients with chronic conditions. This meta-analysis provides the most comprehensive evidence to date that medicinal cannabis improves this patient-centered outcome, with effects that appear to grow rather than diminish over time.

The growing effect size over time (d=0.43 to 0.74) is notable. It suggests either cumulative benefits of sustained cannabis use, dose optimization over time, or selection bias as dissatisfied patients discontinue. The RCT-observational gap also warrants attention.

Observational studies showed larger effects than RCTs, possibly reflecting placebo effects, selection bias, or reporting bias. Only 8% of studies defined what they meant by quality of life. Heterogeneity across conditions and cannabis formulations. Long-term data largely from observational designs.