After a deep review of studies it has been found that medical marijuana is effective to help treat chronic pain, but was less effective in preventing nausea or helping ill patients gain weight.

Medical marijuana’s effectiveness has long been a matter of debate, and 23 US states and the US capital, Washington, have laws that allow medical use of cannabis, along with a number of countries around the world.

The findings presented in the Journal of the American Medical Association were based on a meta-analysis of 79 randomized controlled studies that included a total of nearly 6,500 patients.

Lead researcher Penny Whiting of the University of Bristol, said, “There was moderate-quality evidence to suggest that cannabinoids may be beneficial for the treatment of chronic neuropathic or cancer pain and spasticity due to multiple sclerosis”.

The study showed that the evidence suggesting that cannabinoids were associated with improvements in nausea and vomiting due to chemotherapy, weight gain in HIV, sleep disorders, and Tourette syndrome appeared to be less convincing.

Also marijuana was also found less effective in reducing anxiety, psychosis or depression. Medical marijuana is also linked with a long-list of side effects, including dizziness, dry mouth, nausea, fatigue, euphoria, vomiting, disorientation, drowsiness, confusion, loss of balance and hallucination.

An additional editorial in JAMA by Deepak Cyril D’Souza and Mohini Ranganathan of the Yale University School of Medicine called for more rigorous study of marijuana if used for medical purposes.

They affirmed that if the states’ initiative to legalize medical marijuana is merely an indirect step toward allowing access to recreational marijuana, then the medical community should be left out of the process, and instead marijuana should be decriminalized.