With the increasing use and the legalization of marijuana in several states of USA, there is a need to evaluate its impact on the health. To explore this, a systematic review was recently published in Annals of Internal Medicine by Ravi et al. In the study, the investigators studied the association between marijuana use and cardiovascular outcomes. The authors concluded, “Evidence examining the effect of marijuana on cardiovascular risk factors and outcomes, including stroke and myocardial infarction, is insufficient”.
Ravi and her colleagues summarized evidence from all the studies, since 1975, that enrolled adults who used any form of marijuana, reported cardiovascular risk factors such as hyperglycemia, diabetes, dyslipidemia, and obesity or outcomes such as stroke, myocardial infarction, cardiovascular mortality, and all-cause mortality.
Two studies have associated marijuana use with adverse cardiovascular events. And despite being well designed, the presence of recall bias have limited the generalizability of their results. The metabolic effect of marijuana was a matter of controversy. While some studies showed some benefit, others have shown no or even adverse effect of marijuana on the body metabolism. The authors conclude that there is insufficient evidence to support any of these results. Also, marijuana was not proved to have an association with weight gain.
The authors also address the ethical dilemma of doing randomized clinical trials on marijuana use as the biggest limitation for a better understanding of the impact of marijuana on the health. Most of the currently-available data are from observational studies.
The authors add that most of the studies did not report the timeline of marijuana exposure properly whether it was acute or chronic. Also, the route of administration of marijuana was not standardized in many of the studies.