The US Government's Official Assessment of What Cannabis Can and Cannot Do

What This Report Is (and Isn't)

This is not a single study. It's a consensus report — the closest thing the American scientific establishment has to an official verdict on a question. NASEM committees are convened by the National Academies at the request of government agencies (in this case, prompted by changing state laws and the need for federal guidance). The committee members are chosen for expertise, screened for conflicts of interest, and their conclusions require majority agreement.

The report covers every major health question about cannabis: therapeutic benefits, cancer risk, cardiovascular effects, respiratory effects, immune function, prenatal exposure, psychosocial effects, mental health, addiction, and more. For each, the committee assigned one of four evidence categories based on the strength and consistency of available research.

The Evidence Map

The Three Big Surprises

1. Chronic pain was the strongest therapeutic finding. Not epilepsy, not PTSD, not anxiety. Chronic pain — the condition that affects the most people and intersects most directly with the opioid crisis. This finding became a key argument for medical cannabis advocates and influenced the opioid-cannabis substitution discussion.

2. Epilepsy was rated "insufficient." This seems jarring now, given Epidiolex's FDA approval just 18 months later. But the NASEM committee was reviewing evidence available through 2016, before the definitive Dravet syndrome trials were published. It's a reminder that evidence categories change as research advances.

3. Most claimed benefits had insufficient evidence. For all the conditions people use cannabis to treat — PTSD, depression, IBS, Parkinson's, dementia, glaucoma, opioid dependence — the evidence was rated as limited or insufficient. Not because cannabis doesn't work for these conditions. Because nobody had run the trials to find out.

The Research Barrier Problem

The report's most impactful recommendation may have been its simplest: remove the barriers to cannabis research.

The committee was explicit: the evidence base was thin not because cannabis was understudied relative to its scientific interest, but because regulatory barriers made rigorous research nearly impossible. The Schedule I classification — which assumes no medical value and high abuse potential — was itself preventing the research that could determine whether cannabis has medical value.

This recommendation has been only partially implemented. The DEA expanded research cannabis suppliers in 2021. Rescheduling to Schedule III was proposed in 2024. But as of 2026, the regulatory environment remains substantially more restrictive for cannabis research than for most other substances.

What's Changed Since

The NASEM report was a snapshot of evidence through 2016. Since then:

• Epilepsy has moved from "insufficient" to proven, with Epidiolex FDA approval
• Chronic pain evidence has grown but remains complex — whole-plant cannabis trials still lag behind
• Psychosis risk has been further strengthened by Di Forti's 2019 EU-GEI study
• The opioid relationship has become more nuanced, with population-level data and individual-level studies both supporting cannabis-as-substitute effects
• Sleep remains complicated — the evidence is still mixed

The core finding hasn't changed: for most conditions, the evidence base is thinner than the public assumes. Cannabis research has expanded since 2017, but the gap between what millions of users believe and what controlled trials have demonstrated remains enormous.

Frequently Asked Questions

Does this report prove cannabis works for chronic pain?

The committee found "conclusive or substantial evidence" that cannabis is effective for chronic pain — their strongest therapeutic rating. This doesn't mean cannabis works for all pain types or all people, but the overall evidence was strong enough for scientific consensus. The evidence has continued to grow since 2017.

Why was so much rated 'insufficient'?

Primarily because of research barriers. Cannabis's Schedule I classification made rigorous clinical trials extremely difficult to conduct. The committee wasn't saying cannabis doesn't work for these conditions — it was saying nobody had done the research to find out. The report explicitly called for removing these barriers.

Is this report still relevant?

The evidence categories for some conditions have shifted (epilepsy most dramatically), but the report's core framework remains the reference standard. No comparable comprehensive review has been published since. Many of its "insufficient" ratings remain accurate because the research still hasn't been done.

Can I use this report to justify medical cannabis use?

For chronic pain, chemotherapy nausea, and MS spasticity — yes, the evidence is strong. For most other conditions, the evidence is weaker than many people assume. This report is useful precisely because it's honest about what we know and don't know.