Marijuana and Dopamine: A Study in Complexity

One of the problems created by the war on drugs is how it constrains the ability of researchers to study illicit substances to better understand both their promise for medicine, therapy, and recreation, as well as their potential dangers. While many millions of people find marijuana effective at treating a wide variety of disorders, we still have a fairly poor understanding of which medical conditions it helps with and how, along with what kinds of problems it might create or exacerbate, especially with chronic use.

A paper recently published in Nature suggests that habitual use of marijuana may adversely perturb the brain’s dopamine system (dopamine is a neurotransmitter involved in reward-motivated behavior). Our understanding of the interactions between cannabinoids and dopamine is poor, due to their great complexity. For example, short-term marijuana administration increases dopamine release and neuron activity, though long-term use seems to blunt the dopamine system. And while causal links have not been conclusively established, heavy marijuana use may make it more likely that the consumer develops “mental disorders including psychosis, addition, depression, suicidality, cognitive impairment, and amotivation”.

Unsurprisingly, most of the reporting on the Nature article would leave you with the impression that marijuana use results in negative mental health outcomes. Yet if you read the paper, it is clear that the researchers are aware that the systems they are studying are quite complex and that there are many difficulties in translating animal models into human ones. For example, a common problem with research of this type is the effects from other drugs that are frequently co-administered with marijuana, such as alcohol and nicotine. In addition, people consume a wider variety of cannabinoids (such as CBD, CBN, CBG, etc.), rather than just THC.

This is not to discount the likelihood that overconsumption of marijuana may result in health problems (as is the case with the overconsumption of any substance). One hopes that as the legalization debate thunders on, nuance of what we do and don’t actually know about marijuana isn’t completely lost in favor of cherrypicking whatever findings support your position (as is usually the case). Fortunately, you can read the Nature article for yourself here.


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