BACKGROUND AND PURPOSE:

• Solmi et al. (BMJ, 2023) assessed the associations between cannabis, cannabinoids, and cannabis-based medicines and human health

METHODS:

• Umbrella meta-analysis
• Inclusion criteria
  • Systematic reviews with meta-analyses of observational studies and RCTs
  • Reviews that reported on the efficacy and safety of cannabis, cannabinoids, or cannabis-based medicines
• Study design
  • Credibility was graded
    • RCTs: GRADE criteria
    • Observational studies: Convincing | Highly suggestive | Suggestive | Weak | Not significant
  • Quality was assessed with AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews 2)
• Primary outcome
  • Efficacy and safety of cannabinoids on target symptoms (e.g., seizures in epilepsy)

RESULTS:

• Observational meta-analyses: 50 | RCT meta-analyses: 51
  • High quality: 33 | Moderate: 31 | Low: 32 | Critically low: 5
  • Results from RCTs supported by high to moderate certainty are presented here

For Mixed Conditions

• High certainty: Cannabis-based medicines or cannabinoids
  • Increased the odds of adverse events related to the central nervous system
    • Equivalent odds ratio (eqOR) 2.84 (95% CI 2.16 to 3.73) 
  • Increased the odds of psychological adverse events
    • eqOR 3.07 (95% CI, 1.79 to 5.26)
  • Increased the odds of vision related adverse events
    • eqOR 3.00 (95% CI, 1.79 to 5.03)
• Moderate certainty: Cannabis-based medicines or cannabinoids
  • Increased the odds of nausea or vomit reduction | Pain reduction | Spasticity reduction (global impression of change) | gastrointestinal disorder (non-serious) | Emerging psychiatric disorder | Somnolence
• High certainty: Cannabidiol was associated with
  • A 50% reduction of seizures
    • eqOR 0.59 (95% CI, 0.38 to 0.92)
• Moderate certainty: cannabidiol was associated with
  • Increased pneumonia | Gastrointestinal adverse events | Somnolence

For Chronic Pain

• High certainty: Cannabis-based medicines or cannabinoids
  • Reduced pain by 30%
    • eqOR 0.59 (95% CI, 0.37 to 0.93)
  • Increased psychological distress
    • eqOR 1.76 (95% CI, 1.03 to 3.05)
• Moderate certainty: Cannabis-based medicines or cannabinoids
  • Increased analgesic efficacy | Pain reduction | Change in pain scores

For Epilepsy

• High certainty: Cannabidiol
  • Increased the odds of diarrhoea
    • eqOR 2.25 (95% CI, 1.33 to 3.81)
  • Had no effect on sleep disruption
• Moderate certainty: Cannabidiol
  • Reduced seizures across different populations and measures
  • Improved global impression | Quality of life
  • Increased risk of somnolence

In the General Population

• High certainty: Cannabis
  • Worsened positive psychotic symptoms
    • eqOR 5.21 (95% CI, 3.36 to 8.01)
  • Worsened total psychiatric symptoms
    • eqOR 7.49 (95% CI, 5.32 to 10.42)
• Moderate certainty: Cannabis
  • Worsened negative psychotic symptoms | Cognition
• Similar findings were seen in observational studies

In Healthy People

• High certainty: Cannabinoids
  • Improved pain threshold
    • eqOR 0.74 (95% CI, 0.59 to 0.91)
  • Improved unpleasantness
    • eqOR 0.60 (95% CI, 0.41 to 0.88)

For Inflammatory Bowel Disease

• High certainty: Cannabinoids improved quality of life
  • eqOR 0.34 (95% CI, 0.22 to 0.53)

For Multiple Sclerosis

• Moderate certainty: Cannabinoids
  • Improved spasticity | Pain
  • Increased risk of dizziness | Dry mouth | Nausea | Somnolence

For Cancer

• Moderate certainty: Cannabinoids
  • Improved sleep disruption
  • Increased the risk of gastrointestinal adverse events

Pregnancy (observational studies)

• Convincing evidence that cannabinoids
  • Increase the odds of SGA
    • eqOR 1.61 (95% CI, 1.41 to 1.83)
  • Increase the odds of low birth weight
    • eqOR 1.43 (95% CI, 1.27 to 1.62)

CONCLUSION:

• Cannabis-based medicines have benefits including reducing pain for those with chronic pain conditions, although there is also evidence to support an association with poor mental health  
• There is evidence to support the avoidance of cannabis during pregnancy  
• The authors state

Convincing or converging evidence supports that cannabis use is associated with poor mental health and cognition, increased the risk of car crashes, and can have detrimental effects on offspring if used during pregnancy

Cannabis use should be avoided in adolescents and young adults (when neurodevelopment is still occurring), when most mental health disorders have onset and cognition is paramount for optimising academic performance and learning, as well as in pregnant women and drivers. Conversely, cannabidiol could be considered a potential beneficial treatment option in epilepsy across age groups to reduce seizures

Learn More – Primary Sources:

Balancing risks and benefits of cannabis use: umbrella review of meta-analyses of randomised controlled trials and observational studies

Related ObG Topics:

Is Daily Cannabis Use Linked to Depression and Suicidal Behaviors?

ABCD Study Results: Is There a Link Between Prenatal Cannabis Use and Adverse Psychopathological Effects in Children?

Does Cannabis Use During Pregnancy Increase Risk of Preterm Birth?