Study Questions Effectiveness of Medical Marijuana for Many Conditions

A review of 80 studies of medical marijuana concludes it may be useful for treating certain conditions, but the evidence is weak in supporting the drug’s use for many others. The researchers said any benefits of medical marijuana must be weighed against side effects including nausea, dizziness, dry mouth, sleepiness and euphoria.

The study found moderate-quality evidence to support medical marijuana’s use for chronic pain and muscle spasms, Reuters reports. The researchers said there was only low-quality evidence supporting medical marijuana’s use in treating nausea and vomiting due to chemotherapy, sleep disorders, HIV-related weight loss and Tourette’s syndrome.

“Individuals considering cannabinoids as a possible treatment for their symptoms should discuss the potential benefits and harms with their doctor,” lead researcher Penny Whiting of University Hospitals Bristol NHS Foundation Trust in the United Kingdom told Reuters.

The review appears in JAMA.

A second review published in the same journal concluded there is high-quality evidence supporting the use of marijuana in people with chronic pain, nerve pain and muscle problems related to multiple sclerosis.

“If the primary process by which medications are approved for ‘medical’ use in the U.S. is the (Food and Drug Administration) approval process, then the evidence for many conditions does not meet the existing threshold of evidence,” said Dr. Deepak Cyril D’Souza of Yale University School of Medicine, who co-authored an editorial accompanying the new reviews.

“Both patients and doctors should demand that the government support high-quality research to conclusively determine whether marijuana has therapeutic effects in the various conditions for which it has been currently approved,” D’Souza said.

In the editorial, he noted there is a small but definite risk of psychotic disorder associated with marijuana use, as well as a significant risk of worsening symptoms and relapse in patients with an established psychotic disorder.