What does the research say about the health effects of cannabis?

Due to its categorization as a Schedule 1, federally illegal substance, there is not as much research about cannabis use as anyone would like.  However, the National Academies of Science recently surveyed the research that is available (over 10,000 studies) to publish 100 conclusions on the Health Effects of Marijuana and Cannabis-Derived Products.

Here are some of the most interesting conclusions:

  1. Therapeutic Effects: the review found evidence to support the use of cannabis to treat chronic pain in adults, even “significant reduction in pain symptoms”.

  2. Not Cancer Inducing: smoking cannabis does not increase the risk for cancers often associated with tobacco use. There is insufficient evidence of an association between cannabis use the prostrate, cervical, bladder, or esophageal cancer.

  3. Not a “Gateway” Drug: there is limited evidence that cannabis use increases the use of other drugs. However, there is moderate evidence that there is a link between cannabis use and substance dependence on alcohol, tobacco, and other drugs.

  4. Psychological effects: cannabis use within 24 hours impairs performance in cognition, memory and attention. Cannabis use during adolescence is related to impairments in subsequent academic achievement and education, employment and income, and social relationships and roles.

  5. Respiratory Disease: there is substantial evidence of an association between long-tern cannabis smoking and worse respiratory symptoms and more frequent chronic bronchitis episodes. There is also moderate evidence that improvements in respiratory symptoms occur when cannabis smoking is stopped. There is insufficient evidence to support an association between cannabis smoking and asthma development or exacerbation.

  6. Driving: there is an increased risk of being in a motor accident when cannabis is used prior to driving.

  7. Heart attack: the evidence is unclear on any association between cannabis and heart attack, stroke, or diabetes.

  8. Immunity: there is insufficient data on the association between cannabis use and the immune system.

  9. Pregnancy: smoking cannabis is linked to lower birth weight in the infant, but other neonatal outcomes are unclear.

  10. Mental Health: there is substantial evidence of an association between cannabis use and the development of schizophrenia or other psychoses, especially among frequent users. Cannabis does not appear to increase the likelihood of developing depressions, anxiety, or PTSD. Heavy cannabis users are more likely to report thoughts of suicide than non-users.

The bottom line is that much more research is necessary, and the National Academy of the Sciences includes strong call for more and better research into the short and long term effects of cannabis use on health.

We are starting to see some action in this direction.  UCLA recently launched a Cannabis Research Initiative to properly lead public policy and public health decisions regarding cannabis.  Other universities have also gotten into the research game, including CSU Pueblo, UC San Diego, Humboldt State, and UC Irvine.  It will be exciting and important to learn as much as we can about this powerful plant.