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Research shows use of medical marijuana not always beneficial

July 09, 2015

Excerpted from Medical marijuana: good evidence for some diseases, weak for others,” Reuters. June 23, 2015 — Moderate- or high-quality evidence supports the use of marijuana for some medical conditions, but not for others, according to a fresh review of past research. After reviewing 80 randomized trials that included nearly 6,500 people, researchers found moderate support for using marijuana to treat chronic pain and muscle spasms and involuntary movements.

The evidence wasn't as strong to support marijuana's use for nausea and vomiting due to chemotherapy, sleep disorders, HIV-related weight loss and Tourette syndrome. Also, any benefits of marijuana or cannabis use must be weighed against the risk of side effects, which include dizziness, dry mouth, nausea, sleepiness and euphoria, according to the study's lead author.

The new review, which is published in the Journal of the American Medical Association (JAMA), was commissioned by the Swiss Federal Office of Public Health. The researchers searched medical databases for past randomized controlled trials, which are considered the "gold standard" of medical research. While the researchers found that most trials suggested some improvements in symptoms for the various conditions, not all could suggest the improvement wasn't just due to chance.

A second review published in the same journal by Dr. Kevin Hill of McLean Hospital in Belmont, Massachusetts, found similar results. In that review, Hill found high-quality evidence to support the use of marijuana in people with chronic or neuropathic (nerve) pain, and muscle problems related to multiple sclerosis.


Dr. Munachim UyanwuneAdult Clinical Psychiatrist Munachim Uyanwune, MD: “This article sheds light on the discrepancies in the quality of clinical research regarding medical marijuana use. In addition to this critical issue, it is important to educate clinicians and patients about the risks when using marijuana medically.

“With the use of marijuana to treat various medical symptoms such as nausea, vomiting, weight loss, chronic pain, muscle spasms or others, it is essential that we are informed about its potential negative effects. A common side effect that has been supported by robust research is the association between marijuana use and the onset of psychosis. In a 2012 meta-analysis study by Myles, results noted that the age of onset of psychosis in cannabis users was 32 months earlier than in cannabis non-users. These results showed reliable statistical significance (SMD = -0.399, 95% CI of -0.493 and -0.306, z = -8.34 and p<0.001). They also suggest that cannabis use plays a causal role in the development of schizophrenia. This study was performed to confirm a prior study in the 2011 Journal of American Medical Association (JAMA Psychiatry), which showed the onset of psychosis for cannabis users was 2.7 years younger than for non-users.

“Another risk of marijuana use is the adverse effect it can have on mood symptoms. A 2015 study by Gibbs et. al. in the Journal of Affective Disorders showed a causal risk factor between marijuana use and mania. This study showed marijuana played a role in the occurrence and worsening of manic symptoms. In addition to this, multiple studies have been performed showing effects of marijuana use on neurocognitive functioning. More specifically, they show that acute marijuana use impairs inhibition, promotes impulsivity and affects working memory while long-term use affects executive function.

A more balanced education to clinicians and patients about the risks of medical marijuana should be provided, including its effects on physical and mental health. If we do not, patients could be endangered in cases where the harm and risks of marijuana treatment outweighs its benefits.”


A five-part series on marijuana from Dr. Walt Larimore
The Effects of Marijuana by Donal O'Mathuna
University of Notre Dame Myths and Current Research
The Effects of Marijuana on the Body Infographic

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