Cannabis Use: Umbrella Review Reveals Risks and Benefits for These Populations

The use of cannabis is beneficial for people with chronic pain, multiple sclerosis (MS), and epilepsy; however, there are some populations that should avoid its use, including those with mental health disorders and those who are pregnant. These are the findings of an umbrella review published in The BMJ. 

Although cannabis consumption remains controversial, evidence favoring its utility for the treatment of several health conditions continues to build over time. In most countries, cannabis use is illegal; however, in a small number of countries, its being utilized for both medical and recreational purposes. For the study, researchers conducted an umbrella review of meta-analyses of observational studies on Embase, PubMed, and PsychInfo to determine the association between cannabis use and health benefits. 

Studies included in this analysis were required to be systematic reviews with meta-analyses of observational studies or randomized controlled trials (RCTs) evaluating the efficacy and safety of cannabis, cannabinoids, or cannabis-based medications. 

The co-primary endpoints of this study were the efficacy and safety of cannabinoids on target symptoms. Study credibility and certainty were assessed using GRADE (Grading of Recommendations, Assessment, Development, and Evaluation).

The researchers screened a total of 6657 studies for inclusion and included 101 meta-analyses in this study after exclusion. Of these studies, 51 were meta-analyses of RCTs (364 meta-analytical associations) and 50 were meta-analyses of observational studies (215 meta-analytical associations). There was only 1 meta-analysis that analyzed both RCTs and observational studies. 

Regarding mixed chronic pain conditions, 34 associations were identified from this population and results show that cannabis-based medicine or cannabinoids reduced pain by 30% (equivalent odds ratio [OR], 0.59; 95% CI, 0.37-0.93).

Upon assessment of cannabis use in MS and paraplegia, none of the 18 associations were of high certainty. Pain reduction (n=1) and subjective spasticity (n=1) were associations that were supported with moderate certainty in this population. However, 4 harmful associations were reported with moderate certainty for this population, including dizziness (n=1), dry mouth (n=1), nausea (n=1), and somnolence (n=1). 

The 3 associations identified for IBD or Crohn’s disease showed with high certainty that this population had an improved quality of life (equivalent OR, 0.34; 95% CI, 0.22-0.53).

Of the 46 associations identified among participants with epilepsy, there was high certainty that cannabidiol is associated with diarrhea (equivalent OR, 2.25; 95% CI, 1.33-3.81). Overall, there were 10 beneficial effects and 7 harmful effects associated with cannabis use in participants with epilepsy. 

There were 19 associations showing recreational cannabis use was linked to low birth weight (equivalent OR, 1.43; 95% CI, 1.27-1.62) and small for gestational age (equivalent OR, 1.61; 95% CI, 1.41-1.83).

Among 119 associations in the general population, the researchers found a high potential for harmful effects of cannabis use among adolescents (equivalent OR, 1.71; 95% CI, 1.47-2.00) with high certainty. 

“Law and public health policy makers and researchers should consider this evidence synthesis when making policy decisions on cannabinoids use regulation, and when planning a future epidemiological or experimental research agenda, with particular attention to the tetrahydrocannabinol content of cannabinoids,” the researchers stated. 

Study limitations include the inclusion of evidence from more than a decade ago, potential underestimation of harmful effects of cannabis, and the inability to determine the content and dose of cannabis products used.