Doctors studying marijuana use among patients who self-medicate with the drug as a way to battle depression and anxiety said that there could be a way to adjust an individual's brain function so that it no longer needs marijuana to feel good.

The research, conducted by psychiatry professor Sachin Patel at Vanderbilt University in Nashville, Tennessee, and published in scientific journal Cell Reports, suggests that some of the heaviest marijuana users may be self-medicating — without realizing it — in order to compensate for their brain's low production of THC-like chemicals called endocannabinoids.

"One of the main reasons people use marijuana is to reduce anxiety and cope with stress, and there is a theory out there that people who use marijuana might have a deficiency of their own marijuana-like chemicals in their brain," Patel told VICE News.

Patel and his co-researchers tested this theory on genetically modified mice, bred especially so that their bodies would create low levels of marijuana-like molecules called 2-AG.

"When we analyzed the animals they showed anxiety and depressive behaviors — as much as you can get from animals — and when we were able to give back those molecules, the mice returned to normal," he said.

Patel hypothesized that some anxiety-ridden or depressed marijuana users are likely not making enough of their own THC-like molecules, so are compensating by smoking weed.

"If we're able to normalize their molecules, we might be able to wean them off marijuana," he said of self-medicating users.

Patel explained that the active ingredient in marijuana, THC, binds to a receptor in the brain to create a mood-stabilizing effect, much like opioids — the chemical found in drugs such as heroin and oxycodone — do to create a euphoric effect. Most human brains create enough THC-like chemicals to bind to brain receptors and normalize a person's moods, just as many people can get a euphoric high from naturally produced endorphins.

"Essentially it's the same effect, but people can also use painkillers to [get high] and overwhelm their receptors," he said. "People have found plants to activate their [THC] receptors."

But as well as creating mood stabilizers, the brain also creates an enzyme to break down the 2-AG molecules. For people who have a molecule deficiency, doctors believe a drug to prevent that breakdown could help stabilize a user's mood and reduce their dependence on marijuana. Patel said the implications of his research could one day lead to the manufacture of a medicine that would help people produce more THC-like chemicals in their bodies, and potentially wean addicted users off marijuana.

"If you can prevent that breakdown, you can build up your own supply of natural chemical, that might help people wanting to use marijuana," he said.

The difference between traditional antidepressants and the medicine Patel is describing is that the latter could specifically address low production of THC-like molecules. Traditional medicines have not addressed that problem, which he says contributes to patients seeking relief from marijuana.

When asked why patients would prefer to medicate with a synthetic drug rather than with pot, he said that too much marijuana use is actually counteractive over time; it becomes less effective the more users become dependent on it.

"The problem is — and this has been shown by research groups recently in humans — when people overuse marijuana, THC binds very strongly to brain, and you can't get it to turn itself back down, so desensitization occurs," Patel said. "After people use marijuana chronically, they are shooting themselves in the foot because it leads them to use more drugs to get the same high."

Patel would like to see more research conducted, in order to solidify the connection between low molecule production and depression. The next step after that would be the development of a publicly available medicine, he said. But there's a long road ahead and another big hurdle would be funding.

"We'll have to convince pharmaceutical companies that are able to invest in getting a drug to market that this is something that would be useful," Patel said. "That's the roadblock for a lot of medications."

Patel's research is the latest in a growing body of conflicting studies about marijuana and depression, some of which point to the drug's helpfulness in treating depression, and others that link marijuana to brain changes, depression, other mental disorders, and even suicide.

Follow Colleen Curry on Twitter: @currycolleen