Cannabis Benefits and Risks: What 101 Studies Reveal
What Researchers Found About Chronic Pain and Cannabis
The Study at a Glance
Published
BMJ, 2023
Researchers
University of Ottawa (Canada)
Study Type
Systematic ReviewKey Finding
This comprehensive umbrella review of 101 meta-analyses found high-certainty evidence that CBD effectively reduces seizures in epilepsy, and cannabis-based medicines help chronic pain (30% pain reduction), MS spasticity, and IBD—but also identified clear risks during pregnancy, for mental health, and while driving.
Key Finding: This comprehensive umbrella review of 101 meta-analyses found high-certainty evidence that CBD effectively reduces seizures in epilepsy, and cannabis-based medicines help chronic pain (30% pain reduction), MS spasticity, and IBD—but also identified clear risks during pregnancy, for mental health, and while driving.
What Researchers Studied About Chronic Pain and Cannabis
With cannabis being used for everything from pain to anxiety to epilepsy, researchers needed a definitive answer to the big question: What does ALL the evidence actually show about cannabis benefits and risks?
This 2023 BMJ umbrella review is the most comprehensive analysis ever conducted—examining 101 meta-analyses covering both therapeutic benefits and safety concerns.
Unlike single studies, this "review of reviews" provides the highest level of evidence for understanding where cannabis helps, where it harms, and where we need more research.
How This Systematic Review Was Conducted
Researchers conducted an umbrella review—the highest level of evidence synthesis:
• Analyzed 101 meta-analyses (50 observational studies, 51 RCTs) • Searched PubMed, PsychInfo, Embase through February 2022 • Rated evidence using GRADE (for RCTs) and established criteria for observational studies • Assessed quality using AMSTAR 2 • Covered therapeutic uses AND safety/risk outcomes
Chronic Pain Treatment Results
The Main Results:
- 1CBD reduces seizures by 50% in epilepsy (high certainty evidence)
- 2Cannabis-based medicines reduce chronic pain by 30% (high certainty)
- 3Effective for MS spasticity and IBD quality of life (moderate-high certainty)
- 4Increased risk of psychiatric symptoms in general population (OR 7.49)
- 5Pregnant women: increased risk of low birth weight (43% higher) and small for gestational age (61% higher)
- 6Drivers: 27% increased car crash risk
- 7Adverse events common: CNS effects, psychological effects, GI symptoms
By the Numbers
| Statistic | What It Means |
|---|---|
| 101 | meta-analyses analyzed in this umbrella review |
| 50% | seizure reduction with CBD in epilepsy |
| 30% | pain reduction with cannabis-based medicines |
| 27% | increased car crash risk for drivers who use cannabis |
meta-analyses analyzed in this umbrella review
seizure reduction with CBD in epilepsy
pain reduction with cannabis-based medicines
increased car crash risk for drivers who use cannabis
What This Means for Chronic Pain Patients
This landmark review provides the clearest picture yet of cannabis benefits and risks:
Where cannabis clearly helps (high certainty): • Epilepsy: CBD reduces seizures by 50% • Chronic pain: 30% more patients achieve meaningful relief • MS: Reduces spasticity and pain • IBD: Improves quality of life
Where cannabis causes harm (convincing evidence): • During pregnancy: Increases risk of low birth weight, small babies • Mental health: Worsens psychotic symptoms, especially in prone individuals • Driving: 27% higher crash risk
Who should avoid cannabis: • Adolescents and young adults • People with or prone to mental health disorders • Pregnant women • Anyone before or while driving
Bottom line: Cannabis has legitimate medical uses for specific conditions, but it's not without risks. The evidence strongly supports using CBD for epilepsy and cannabis-based medicines for chronic pain and MS, while clearly showing who should avoid it.
Quick Answers: Chronic Pain and Cannabis
Direct answers based on the findings of this study:
Research Summary: Answers are based on published peer-reviewed studies and represent research findings, not medical recommendations. Individual results may vary. Always consult a healthcare provider before making treatment decisions.
Is marijuana safe?
Depends on who and why. A 2023 BMJ review of 101 studies found it helps epilepsy, chronic pain, and MS—but increases psychiatric risk (7x), crash risk (27%), and pregnancy harm. Safe for some, not for teens, pregnant women, or before driving.
Source: Solmi et al., BMJ, 2023 (PMID: 37648266)
What does marijuana actually help with?
High-quality evidence shows cannabis helps: epilepsy (CBD cuts seizures 50%), chronic pain (30% get relief), MS spasticity, and IBD quality of life. Cancer nausea also responds well according to a 2023 BMJ review of 101 studies.
Source: Solmi et al., BMJ, 2023 (PMID: 37648266)
Is it safe to smoke weed while pregnant?
No—definitely avoid. A BMJ review found cannabis during pregnancy increases risk of undersized babies (61% higher) and low birth weight (43% higher). The evidence on this is convincing. Don't use cannabis if pregnant.
Source: Solmi et al., BMJ, 2023 (PMID: 37648266)
This is educational content, not medical advice
The research summarized here is for informational purposes only. Individual results may vary, and what works in studies may not work the same way for everyone. Always consult with a qualified healthcare provider before making changes to your treatment plan or starting medical cannabis therapy.
Important Limitations
This study has some caveats to keep in mind when interpreting the results:
- Umbrella review depends on quality of underlying meta-analyses
- Different cannabis preparations across studies make direct comparisons difficult
- Long-term effects still need more research
- Recreational vs medical use not always distinguished
- Some conditions had limited high-quality evidence
The Bottom Line on Cannabis for Chronic Pain
This definitive BMJ umbrella review of 101 meta-analyses confirms that cannabis-based medicines are effective for epilepsy, chronic pain, MS spasticity, and IBD—but also identifies clear populations who should avoid cannabis: pregnant women, adolescents, those with mental health disorders, and drivers. For patients with qualifying conditions, the evidence supports careful use under medical supervision. For everyone else, the risks may outweigh the benefits.
Do You Qualify for Medical Marijuana?
If you're living with Chronic Pain, you may qualify for a medical marijuana card. Our licensed physicians can evaluate you from home via telehealth.
Related Research & Resources
Related Research
- Cannabis for Pain: A Complete Overview of the Evidence
- What Does Science Actually Know About Medical Cannabis?
- Does Cannabis Really Help Chronic Pain? What 32 Clinical Trials Found
- Cannabis for Chronic Pain: A Critical Look at 104 Studies
- Clinical Practice Guidelines: Cannabis for Chronic Pain & Co-Occurring Conditions (2024)
Condition Research
Get Your Card
This condition qualifies for medical marijuana in:
Source
Solmi M, De Toffol M, Kim JY, et al. "Balancing risks and benefits of cannabis use: umbrella review of meta-analyses of randomised controlled trials and observational studies" BMJ. 2023. DOI: 10.1136/bmj-2022-072348
Important Information
Not Medical Advice: This research summary is for educational purposes only. It should not be used to diagnose, treat, cure, or prevent any disease or medical condition. Always consult a qualified healthcare provider before starting or changing any treatment.
Individual Variation: Research findings represent group averages. Your individual response to cannabis may differ based on genetics, other medications, underlying conditions, and many other factors.
Last reviewed: January 24, 2026
Important Notices
Research Summary Disclaimer
This content represents our interpretation of published scientific research for educational purposes. It should not be used to make treatment decisions without consulting a qualified healthcare provider. Individual results may vary from study findings.
FDA Notice
These statements have not been evaluated by the FDA. Cannabis is not intended to diagnose, treat, cure, or prevent any disease. The FDA has not approved cannabis for any medical condition except specific prescription medications.
Copyright & Fair Use
Research summaries are provided under fair use (17 U.S.C. § 107) for educational purposes. We provide brief summaries with attribution, not full reproductions. All studies remain the intellectual property of their respective authors and publishers.
Data Sources
Study information sourced from PubMed®, U.S. National Library of Medicine. Inclusion does not imply endorsement by NLM, NIH, or the federal government.
For complete information, see our Terms of Use and Research Content Policy.
FAQs: Cannabis for Chronic Pain
Is cannabis safe to use?
It depends on who you are and why you're using it. A 2023 BMJ review of 101 studies found cannabis is effective for epilepsy, chronic pain, and MS, but poses risks for pregnant women, adolescents, those with mental health issues, and drivers.
Does CBD help epilepsy?
Yes, with high certainty. The umbrella review found CBD reduces seizures by 50% in epilepsy patients, which is why CBD (Epidiolex) is FDA-approved for certain epilepsy conditions.
Can you use cannabis while pregnant?
No. Convincing evidence shows cannabis use during pregnancy increases risk of low birth weight (43% higher) and small for gestational age babies (61% higher). Pregnant women should avoid cannabis.