As state lawmakers move to decriminalize marijuana for medical and recreational use, the cannabis economy is simultaneously gaining momentum. As it does, there's been much discussion — and research — focused on how marijuana affects the human body and mind. In particular, researchers and marijuana advocates have devoted a fair bit of attention to the relationship between cannabis use and depression.
Though regular marijuana users tend to be diagnosed with depression more frequently than those who don't use cannabis, marijuana does not cause depression, wrote Dr. Daniel K. Hall-Flavin for Mayo Clinic.
"It's likely that the genetic, environmental or other factors that trigger depression also lead to marijuana use," Hall-Flavin wrote for the Mayo Clinic. "Some people with depression may use marijuana as a way to detach from their depressive symptoms. Heavy users may appear depressed as a result of the dulling effects of the drug on feelings and emotions."
A recent study published in JAMA Psychiatry supports Hall-Flavin's statement. After a nationwide longitudinal study of nearly 35,000 Americans aged 18 and up, researchers concluded that marijuana users are no more likely to develop anxiety or mood disorders than those who don't use the drug.
And in fact, according to a separate study, marijuana may reduce the symptoms of depression. "Chronic stress is one of the major causes of depression," explained Samir Haj-Dahmane, a senior research scientist at the University at Buffalo's Research Institute on Addictions, in a Feb. 4 press release. "Using compounds derived from cannabis — marijuana — to restore normal endocannabinoid function could potentially help stabilize moods and ease depression."
Despite those findings, Haj-Dahmane was quick to point out that further research on the relationship between depression and marijuana use is necessary. "Our research thus far has used animal models; there is still a long way to go before we know whether this can be effective in humans," he said in the release. "However, we have seen that some people who suffer from post-traumatic stress disorder have reported relief using marijuana."
Yet another survey of more than 4,400 adults, organized by the Center for Epidemiological Studies, concluded that neither frequent nor infrequent cannabis use increased a person's likelihood of depression.
Though studies suggest that marijuana use may not increase the risk of depression, the drug has been linked to other psychological disorders, such as schizophrenia or psychosis for those who are already prone to psychosis. And according to Hall-Flavin, teenagers who've attempted suicide are also more likely to have either experimented with cannabis or are regular users of the drug.
In his statement to the Mayo Clinic, Hall-Flavin's conclusion is clear: "Marijuana use and depression accompany each other more often than you might expect by chance, but there's no clear evidence that marijuana directly causes depression."
So far, 23 states and Washington, D.C. have legalized marijuana in some form. And despite its controversial possible legality in some states, Leafly predicted that Nevada, California, Maine, Arizona, Connecticut, Michigan, Ohio, Rhode Island and Vermont are among the states that could move to decriminalize marijuana in 2016.