Systematically Testing the Evidence on Marijuana

Living systematic review

Search (updated: February 2023 to May 2025):

• Ovid MEDLINE ALL
• PsycINFO
• CENTRAL
• ClinialTrials.gov

Screening: Studies (controlled clinical trials and observational studies with comparison groups) assessed the effects of plant-based cannabis preparations; whole-plant extracts (e.g., nabiximols); or US Food and Drug Administration (FDA)-approved synthesized, pharmaceutically prepared cannabinoids (e.g., dronabinol, nabilone) in adults with a diagnosis of anxiety or mood disorder. Minimum 4 weeks of follow-up.

Risk of Bias (RoB): Tool adapted from those used by national organizations, including SIGN, NICE and the National Heart‚ Lung‚ and Blood Institute.

GRADE: Overall certainty of evidence (CoE) for each outcome was determined using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach

Updates: Search to be updated at regular intervals

• We included 14 studies.
• We also identified 6 ongoing studies on this topic.

Anxiety disorders (5 studies)

• Cannabidiol (CBD)
  • CBD may be associated with improvements in anxiety, depression, and other anxiety-related symptoms (low-certainty evidence).
  • It is unclear from the available evidence whether CBD impacts functioning or safety (very low certainty evidence).
  • No evidence for health care utilization.
• Tetrahydrocannabinol (THC)
  • It is unclear from the available evidence whether THC impacts anxiety symptoms or safety (very low certainty evidence)
  • No evidence for quality of life (QoL) and functioning, or health care utilization.

Depressive disorders (1 study)

• Cannabis use (THC vs CBD not assessed)
  • It is unclear from the available evidence whether cannabis use impacts depression symptoms, QoL or functioning, or healthcare utilization.

Bipolar disorders (8 studies)

• CBD
  • It is unclear from the available evidence whether CBD impacts depression symptom control and safety in patients with bipolar disorder.
  • No evidence for CBD and quality of life and functioning, or health care utilization.
• Cannabis use (THC vs CBD not specified)
  • There is consistent evidence across nonrandomized studies that cannabis use may be associated with increased risk of mania and other bipolar-related symptoms, as well as poorer disease outcomes, such as recovery and remission (low-certainty evidence).
  • It is unclear from the available evidence whether cannabis use impacts quality of life and functioning, and health care utilization.
  • No evidence for safety.

Summary of Findings (GRADE)

Note. ^a Inconsistency not assessed; single study only.
Abbreviations. AE: adverse event; CBD: cannabidiol; CCT: controlled clinical trial; CoE: certainty of evidence; CUD: cannabis use disorder; GRADE: Grading of Recommendations, Assessment, Development, and Evaluations approach; MDD: major depressive disorder; NRS: nonrandomized study; RCT: randomized control trial; RoB: risk of bias.

• The evidence for cannabis and anxiety and mood disorder-related outcomes is uncertain overall. However, evidence does suggest that CBD may improve symptoms in those with anxiety, while people with bipolar disorder who use cannabis may experience poorer outcomes overall.
• More research is urgently needed to address increasing interest in cannabis use for mental health disorders.

• No evidence on quality of life or functioning for cannabis and anxiety disorders, nor for safety of cannabis for depressive and bipolar disorders.
• High quality, randomized studies of cannabinoids are needed to determine whether cannabis has any effects on anxiety or mood disorders.
• We identified 6 ongoing, phase 3 or 4 RCTs of cannabis in anxiety, depression, or other mood disorders expected to be completed in the coming years.