New research helps explain why marijuana can provoke paranoia in some users.
Marijuana has an interesting effect on anxiety. Some report paranoia after using marijuana, while others report a reduction in anxiety. Now, scientists from Vanderbilt University have uncovered evidence that may explain marijuana’s complicated relationship with feeling anxious.
The findings, published March 5 in the journal Neuron, are the first to confirm that cannabinoid receptors are indeed present in the part of the brain that regulates anxiety and fear: the amygdala. Cannabinoid receptors are activated by chemicals in marijuana, called cannabinoids, and have been identified in many other brain regions as well.“We know where the receptors are, we know their function”Research by Canadian scientists first suggested that marijuana may enhance fear-based learning by acting on pathways in the amygdala. In 2011, a team at the University of Western Ontario found that THC intensified how rats reacted to certain smells that they were trained to fear. But up till now, no group has managed to characterize the amygdala’s cannabinoid pathways in such detail.
“We know where the receptors are, we know their function, we know how these neurons make their own cannabinoids,” explained study author Dr. Sachin Patel in a university release.
“Now can we see how that system is affected by… stress and chronic (marijuana) use? It might fundamentally change our understanding of cellular communication in the amygdala.”
Dr. Patel’s new study links marijuana directly to the area of the brain that regulates the fight-or-flight response. This response is part of the body’s overall process of reacting to factors of threat or stress.
But why certain people feel more anxious after using marijuana and others less is still unclear. The researchers used antibody-labeled imaging techniques to look at the activity of the body’s own cannabinoids, rather than those derived from the plant. Humans, and many animals, naturally produce a set of marijuana-like chemicals known as endocannabinoids.
The study, which was conducted on mice, also showed for the first time that endocannabinoids are produced by nerve cells within the amygdala. The team identified two separate mechanisms that could explain marijuana’s opposite effects on anxiety. Interestingly, endocannabinoids seem to primarily act to reduce anxiety and fear responses.“Marijuana users say they take the drug mainly to reduce anxiety”The researchers conclude that more studies are needed to explain why marijuana use sometimes results in increased paranoia.
At the same time, Dr. Patel notes, “the discovery may help explain why marijuana users say they take the drug mainly to reduce anxiety.” Indeed, marijuana has received significant interest as a potential treatment for post-traumatic stress disorder (PTSD) — a severe type of anxiety disorder.
The team also points out that regular marijuana use can desensitize the brain’s cannabinoid receptors over time. Perhaps this could explain why novice cannabis users are more prone to paranoid side effects than experienced users. But ultimately, more research is needed to say for sure.