For most conditions that qualify for medical marijuana, there isn't enough evidence to support it yet | Research

The takeaway

A review of evidence across 13 state-approved medical marijuana conditions found insufficient evidence for most, with the strongest support limited to chronic pain and muscle spasticity.

Read this if you're considering medical marijuana and want to know what the evidence actually supports.

Insufficient evidence for most of the 13 state-approved conditions

What the researchers found

Researchers reviewed the scientific evidence for cannabis treatment across the conditions most commonly approved by state medical marijuana programs. They identified 13 conditions shared by at least 80% of medical marijuana states: Alzheimer's disease, ALS, cachexia, cancer, Crohn's disease, epilepsy, glaucoma, hepatitis C, HIV/AIDS, MS/spasticity, severe pain, severe nausea, and PTSD.

For the majority of these conditions, the reviewers found insufficient evidence to support recommending medical marijuana. The strongest evidence existed for chronic pain and muscle spasticity. For other conditions, the available data consisted largely of anecdotal reports, small uncontrolled studies, or preclinical research.

The authors stressed the need for rigorous research comparing smoked marijuana to existing treatments, examining safety, tolerability, and efficacy across different formulations.

Why it matters

State medical marijuana programs approve conditions based on political and social factors as much as scientific evidence. This review highlights the gap between what is legally approved and what is scientifically supported, emphasizing the need for more research.

The numbers in context

13 conditions reviewed across state medical marijuana programs. Shared by at least 80% of medical marijuana states. PTSD was the only psychological condition approved. Insufficient evidence found for the majority of conditions.

How the study worked

Narrative review using literature searches in PsycINFO, MEDLINE, and Google Scholar. Included studies relevant to the 13 most commonly state-approved conditions for medical marijuana, plus PTSD as the sole approved psychological condition.

What this study cannot tell us

Narrative review methodology means study selection was not exhaustive. Publication date (2015) means newer evidence was not included. The review focused on smoked marijuana and may have underrepresented pharmaceutical cannabinoid research.

How to read the evidence

Narrative review synthesizing evidence across multiple conditions. Quality of underlying evidence varied widely.

When this study was published

Published in 2015. Evidence for several conditions has been updated since.

The bigger picture

Medical marijuana legalization has outpaced the scientific evidence supporting it for most approved conditions. This does not mean cannabis is ineffective for these conditions, but rather that the research has not been done to confirm or deny it with confidence.

Questions still open

Should state-approved conditions require a minimum evidence threshold? Has the evidence improved for any of these conditions since 2015? Are there conditions where cannabis is actively harmful rather than just unproven?

Common questions

Does medical marijuana work for all the conditions it's approved for?

As of this 2015 review, the evidence was insufficient for most state-approved conditions. The strongest support existed for chronic pain and muscle spasticity. For conditions like Alzheimer's, glaucoma, and PTSD, rigorous evidence was largely lacking.

Why is marijuana approved for conditions without strong evidence?

State approval processes are influenced by political, social, and patient advocacy factors alongside scientific evidence. The authors noted that many conditions were approved based on anecdotal or preclinical evidence rather than controlled clinical trials.

Read the original research

Narrative review of the safety and efficacy of marijuana for the treatment of commonly state-approved medical and psychiatric disorders.

Addiction science & clinical practice, 10, 10

View on PubMed ↗Publisher’s paper ↗

Citation

Belendiuk, Katherine A; Baldini, Lisa L; Bonn-Miller, Marcel O. (2015). Narrative review of the safety and efficacy of marijuana for the treatment of commonly state-approved medical and psychiatric disorders.. Addiction science & clinical practice, 10, 10. https://doi.org/10.1186/s13722-015-0032-7