Systematic review: medicinal cannabis may offer short-term mental health relief but is not a cure

High doses of CBD provided some acute relief in anxiety disorders. CBD/THC combinations alleviated withdrawal symptoms in cannabis use disorder and improved sleep. THC was associated with dose-dependent adverse events and, in some psychosis studies, worsened primary outcomes. No study found long-lasting medicinal effects or improvement.

Researchers searched PubMed, PsycInfo, Embase, and Cochrane Library across two search periods (October 2023 and July 2024), screening 18,341 studies. Forty-nine controlled studies from 15 countries were included, covering treatment-seeking participants using medicinal cannabis for their mental health diagnosis.

As medicinal cannabis use for mental health grows globally, this review provides the most comprehensive controlled-study assessment to date of what works, what does not, and what carries risks across a wide range of psychiatric diagnoses.

The split between product types is critical: CBD appears to help with anxiety, while THC carries risks in psychosis and shows dose-dependent adverse events. Naturalistic studies where participants self-reported THC benefits conflicted with clinical trial findings, highlighting a gap between perceived and measured effects. The absence of any long-term improvement across all studies is a significant finding.

Risks of bias were prevalent across included studies. Product compositions, doses, and delivery methods varied widely. Naturalistic and clinical trial findings sometimes contradicted each other. Many diagnoses had very few qualifying studies.