Why we Think It’s Important: 

The comprehensive findings from this review paper serve as a valuable resource for informing public health policies and guidelines related to the use of cannabis, cannabinoids, and cannabis-based medicines. 


The systematic assessment of the associations between cannabis, cannabinoids, and cannabis-based medicines with human health, conducted through an umbrella review, offers crucial insights into the potential benefits and risks associated with their use. The review, encompassing a comprehensive analysis of systematic reviews with meta-analyses of both observational studies and randomized controlled trials, draws from extensive data sources, including PubMed, PsychInfo, and Embase, up to February 9, 2022. 

A total of 101 meta-analyses were included in the review, with a balanced distribution between 50 observational studies and 51 randomized controlled trials. The methodological quality of these studies was rigorously assessed using AMSTAR 2, with 33 classified as high quality, 31 as moderate, 32 as low, and 5 as critically low. AMSTAR 2 is a critical appraisal tool designed to assess the methodological quality of systematic reviews by evaluating key aspects such as research question formulation, study selection processes, and consideration of study quality in the analysis. It helps users gauge the reliability and trustworthiness of systematic reviews, aiding evidence-based decision-making in fields like medicine and research. The findings from randomized controlled trials, supported by high to moderate certainty, revealed noteworthy outcomes related to cannabis-based medicines. In individuals with mixed conditions, these medicines were associated with increased adverse events concerning the central nervous system, psychological effects, and vision. 

Moreover, the impact of cannabidiol (CBD) was explored, showing its effectiveness in reducing seizures and seizure events in epilepsy patients. However, this came with an increased risk of pneumonia, gastrointestinal adverse events, and somnolence. In the context of chronic pain, cannabis-based medicines or cannabinoids demonstrated a reduction in pain by 30%, albeit with an increase in psychological distress. For epilepsy, CBD exhibited a higher risk of diarrhea but showed positive effects on reducing seizures and improving overall quality of life. 

In the general population, cannabis use was linked to worsening positive psychotic symptoms, total psychiatric symptoms, negative psychotic symptoms, and cognition. Conversely, in healthy individuals, cannabinoids were found to improve pain threshold and unpleasantness. The review also shed light on the impact of cannabis on various medical conditions, including inflammatory bowel disease, multiple sclerosis, and cancer. While cannabinoids showcased positive effects on certain symptoms, such as improving quality of life in inflammatory bowel disease and relieving spasticity and pain in multiple sclerosis, adverse events like dizziness, dry mouth, nausea, and somnolence were noted. 

The evidence from observational studies, especially in pregnant women, drivers, and the general population, was found to be convincing in supporting harmful outcomes. These included small gestational age, low birth weight, car crashes, and psychosis. Additional harmful effects were noted in neonatal outcomes, car crashes, psychotic symptoms, suicide attempts, depression, mania, and impaired cognition in healthy cannabis users. 

In conclusion, the umbrella review presents convincing and converging evidence that supports the avoidance of cannabis during adolescence, early adulthood, pregnancy, and before or while driving. While CBD shows effectiveness in epilepsy, cannabis-based medicines demonstrate efficacy in multiple sclerosis, chronic pain, inflammatory bowel disease, and palliative care, albeit with associated adverse events. The comprehensive findings serve as a valuable resource for informing public health policies and guidelines related to the use of cannabis, cannabinoids, and cannabis-based medicines. 

For readers interested in a deeper dive into the findings and methodologies, the full article can be accessed here 

“Balancing risks and benefits of cannabis use: umbrella review of meta-analyses of randomised controlled trials and observational studies.” (M. Solmi, et al., BMJ, 2023)