Epilepsy, multiple sclerosis and chronic pain might improve, but teens, young adults and pregnant women might face elevated risks.

As medicinal and recreational cannabis use increases and is legalised in many parts of the USA, evidence of the potential benefits and harms of cannabinoids continues to accumulate. Investigators conducted an umbrella review of 101 meta-analyses of studies that associated cannabinoid use with various outcomes in humans (50 meta-analyses combining data from observational studies and 51 from randomised controlled trials), seeking ‘converging findings from different study designs.’

Associations with cannabinoids with at least suggestive evidence in observational studies or moderate certainty in RCTs included the following: 

• lower risk for seizures in various forms of epilepsy, reduced pain and spasticity in multiple sclerosis, and better pain control in palliative care and various other conditions
• higher risk for psychosis in the general population, particularly among adolescents, and higher risk for relapse in patients with previous psychosis
• higher risk for other psychiatric symptoms, including depression and mania, as well as deficits in recall and learning
• higher risk for motor vehicle crashes, perhaps mediated by higher risks for somnolence, dizziness and vertigo
• higher incidence of babies with low birth weight after use in pregnancy.

Comment: Based on these findings, the authors suggest that cannabis be avoided by adolescents, young adults and people prone to mental illness – all groups at elevated risk for excessive cannabis use – as well as by pregnant women and drivers. However, this review is limited by the inherent limitations of observational data, the short duration of most randomised trials and heterogeneity in the types and doses of cannabinoids used in different studies.

Bruce Soloway, MD, Associate Professor Emeritus of Family and Social Medicine, Albert Einstein College of Medicine, Bronx, New York, USA.

Solmi M, et al. Balancing risks and benefits of cannabis use: umbrella review of meta-analyses of randomised controlled trials and observational studies. BMJ 2023; 382: e072348.

This summary is taken from the following Journal Watch titles: General Medicine, Pediatrics and Adolescent Medicine, Psychiatry, Ambulatory Medicine.