Overview of Why cannabis’s health effects are so hard to study
This Science Friday conversation explores why cannabis research is unusually difficult: the market is full of products with different compounds, doses, and delivery methods, while laws and regulations have changed faster than the science. Guests Ryan Vandre of Johns Hopkins and Natasha Wade of UCSD discuss what researchers know so far about cannabis’s potential benefits, its risks for teens, and why better evidence is still urgently needed.
Why cannabis is difficult to study
A rapidly changing market
- Cannabis is no longer just smoked flower; it now includes:
- inhaled products
- edibles/oral doses
- topicals
- suppositories
- numerous formulations and devices
- Researchers have to study not just “cannabis,” but:
- dose
- route of administration
- product composition
- user age and experience
- whether it’s used medically or recreationally
Many compounds, many variables
- Unlike alcohol, which is a single molecule, cannabis contains many active compounds, including:
- THC
- CBD
- CBN
- CBG
- other cannabinoids and chemicals
- That complexity makes it hard to generalize findings from one product to another.
Regulation and product claims outpace science
- The guests argue the cannabis market has had few guardrails around product claims.
- Scientists are often “playing catch-up” as new products appear before their effects are well understood.
What the research says so far
Findings on teens and brain development
Natasha Wade described a long-running study of about 11,000 children followed from childhood into adolescence.
Key findings:
- Teens who started using cannabis did not show the same improvements in thinking ability as peers who did not use it.
- The effect remained even after controlling for many factors, including:
- alcohol and nicotine use
- prenatal exposure
- early childhood factors
- mental health concerns
- family and demographic variables
- This does not prove causation, but it suggests a meaningful association between cannabis use and reduced cognitive gains during a critical developmental period.
Co-use is becoming more common
- Teens are increasingly using cannabis alongside nicotine products.
- That mix may change both the experience and long-term effects, but the science is still unsettled.
Where cannabis shows medical promise
Conditions with the strongest evidence or promise
Ryan Vandre said cannabis and cannabinoids show promise for:
- pain
- chemotherapy side effects
- rare forms of epilepsy involving CBD
- possibly:
- PTSD
- autism
- Parkinson’s disease
- agitation in dementia
Why “getting high” may not be necessary
- Some medical benefits may occur at very low THC doses that do not produce intoxication.
- He cited research suggesting even sub-milligram THC doses may help with chronic pain in some settings.
- This supports the idea that future cannabinoid medicine may focus on isolating specific compounds rather than using the whole plant as a “blunt tool.”
How policy affects research
Federal classification creates barriers
- Cannabis’s legal status limits access to standardized, regulated products for research.
- Patients may not disclose cannabis use to doctors, and use often isn’t captured clearly in medical records.
- That makes it hard to study real-world outcomes across conditions like:
- epilepsy
- autism
- Parkinson’s
- insomnia
Rescheduling could help, but only partly
- Moving some cannabis products to a less restrictive schedule could make research easier.
- It may allow researchers to buy dispensary products for lab studies and improve access to information about patient use.
- But it would not solve all issues, since the market still contains many different products with inconsistent formulations.
Practical advice for consumers and teens
For adults shopping for cannabis products
The guests emphasize:
- learn the differences between product types
- understand how delivery method changes effects
- talk to your doctor, especially if using cannabis for health reasons
- start low and go slow
- remember that therapeutic benefit does not always require intoxication
For teens
Natasha Wade’s advice is simple:
- wait as long as possible
- the adolescent brain is still developing
- if someone is looking for a “high,” other activities can provide that feeling without the same risks
- she sees little evidence of clear benefit for generally healthy teens and some evidence of harm
Main takeaways
- Cannabis is hard to study because it is chemically complex, highly variable, and rapidly evolving.
- The strongest concerns involve teen brain development and the possibility that cannabis may slow normal cognitive gains.
- Cannabis has real therapeutic promise, especially for pain and certain medical conditions, but the field still lacks enough standardized evidence to make broad recommendations.
- Researchers see the field as both challenging and exciting because it has major public health and policy implications.