Marijuana (Cannabinoids)

Medical marijuana: Clinical limitations and safety concerns

Dr. Matthew Seamon from Nova Southeastern University College of Pharmacy, in Fort Lauderdale, Florida has reviewed the evidence.

Here’s what you need to know.

Evidence supporting its use

  • Much of the available data is marginal, with mixed results.
  • Thus, much of the “effectiveness” of medical marijuana is anecdotal.
  • This is not to say that marijuana is ineffective or the data are strictly lacking.

Cautious endorsements

  • American Cancer Society
    • Research results are mixed, although they support the rights of individuals to decide treatment.
  • The National Multiple Sclerosis Society
    • Acknowledges a clear potential role.
    • Does not support widespread availability, based on the available data and known risks.
  • The American Medical Association
    • Supports regulating marijuana as a Schedule I drug.
    • There is a need for further research.


  • Most risks are mild and involve central nervous system and gastrointestinal effects.
  • Dizziness is the most common adverse effect.
  • Nausea, feelings of euphoria, and irritability are also reported.
  • Also associated with…
    • Memory and learning defects
    • Psychiatric disturbances
    • Respiratory problems
    • Cancer
    • Cardiovascular complications
    • Male infertility
    • Periodontal disease
    • Bone loss
    • Sleep disturbance
    • Aluminum and other heavy metal accumulation
    • Addiction, dependence, and withdrawal
  • Marijuana interacts with warfarin to increase the bleeding risk.
  • It may potentiate the effects of opioids and CNS depressants like benzodiazepines, muscle relaxants, and alcohol.
  • Marijuana also reportedly interacts with a number of antidepressants and neuroleptics.

The bottom line?

Medical marijuana is a politically charged topic within healthcare organizations, and their official positions reflect this.

Proponents always tell us the benefits are well documented. But don’t be fooled.

Considering the discrepancy between what we know about the effectiveness of medical marijuana and what we know about its safety, it would be (at the very least) shortsighted to trust your health needs to any form of marijuana.

3/2/10 20:12 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.