Health Effects of Marijuana According to the Institute of Medicine

During the past two decades, a growing number of states have legalized cannabis and/or cannabidiol (a cannabis component) for medical and/or recreational use, yet evidence about both the short- and long-term health impact of their use remains unclear. In an attempt to bring some clarity to the situation, a team of researchers from the Institute of Medicine sifted through 24,000 sources of information on marijuana. The end result was a 468-page document entitled “The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research.”

The report does not come to any conclusions about whether marijuana should be legalized. Rather, the authors noted that a “lack of evidence-based information…,poses a public health risk” and fall back on stating that there is a “need for definitive clinical research” before any final decisions can be made.

However, the team did reach numerous conclusions on the therapeutic effects of cannabis and cannabinoids for a wide variety of health conditions. These conclusions may be comforting and reassuring for some while disappointing or confusing for others. The promising news is that research is definitely continuing in this arena, and interest remains very strong.

How effective is marijuana for medical conditions

Here is an overview of the conditions for which there is varying degrees of evidence of effectiveness for cannabis or cannabinoids.

  • Conclusive or substantial evidence of effectiveness for treatment of chronic pain in adults, chemotherapy-induced nausea and vomiting, and patient-reported spasticity symptoms associated with multiple sclerosis
  • Moderate evidence of effectiveness for improving sleep in people with sleep problems associated with fibromyalgia, chronic pain, multiple sclerosis, and obstructive sleep apnea syndrome
  • Limited evidence of effectiveness for improving symptoms of Tourette syndrome, improving anxiety in people with social anxiety disorders, increasing appetite and reducing weight loss in HIV/AIDS patients, improving spasticity symptoms in multiple sclerosis as measured by clinicians, and improving symptoms of posttraumatic stress disorder

In addition, the researchers concluded there is limited evidence that marijuana is not effective for improving symptoms of dementia, reducing depressive symptoms in people with multiple sclerosis or chronic pain, or improving intraocular pressure associated with glaucoma.

Finally, the authors reported there was no or insufficient evidence to support or refute effectiveness for the following conditions: cancers (including glioma), anorexia nervosa, cancer-associated anorexia cachexia syndrome, irritable bowel syndrome symptoms, epilepsy, ALS symptoms, Huntington’s disease symptoms, or motor system symptoms associated with Parkinson’s disease.

What are the health impacts of marijuana use

The authors reached dozens of conclusions about associations between cannabis and cannabinoid use and their health impacts in the areas of respiratory health, cancer, cardiovascular health, prenatal health, immune system, mental health, and injury and death. Some of the highlights include the following:

  • There is moderate evidence of no statistical association between use of marijuana and the incidence of cancer of the lung, head, or neck
  • No or insufficient evidence to support or refute a statistical relationship between marijuana use and the incidence of prostate cancer, penile cancer, anal cancer, bladder cancer, esophageal cancer, or non-Hodgkin lymphoma
  • However, there is substantial evidence of a statistical association between marijuana use and (1) more frequent episodes of chronic bronchitis (with long-term smoking); (2) risk of motor vehicle accidents; (3) low-birth weight infants among mothers who smoke; and (4) development of schizophrenia or other psychoses, especially with frequent use.

Please see a complete list of the conclusions for more information.

Study recommendations

The authors also set forth an extensive list of research recommendations that addresses the significant gaps in research, how to improve the quality of research and surveillance of cannabis use, and the many barriers to research. They acknowledge the numerous challenges that face them, including regulatory barriers, access to the type of cannabis necessary to conduct the research they want to do, availability of funding for research, and the need for improvements and standardization in research methods.


National Academies of Sciences, Engineering, and Medicine et al. The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Washington (DC): National Academies Press (US): 2017 Jan 12.