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Mixed Results With THC Antidepressants

Cannabis seedsA new study has found that a synthetic form of THC, the active ingredient in cannabis, is an effective antidepressant at low doses.

However, at higher doses, the effect reverses itself and can actually worsen depression and other psychiatric conditions like psychosis.

The study is published in The Journal of Neuroscience.

Scientists have been known for many years that depletion of the brain neurotransmitter serotonin, leads to depression.

Common SSRI-class antidepressants like Prozac and Celexa work by enhancing the available concentration of serotonin in the brain. However, this study offers the first evidence that cannabis can also increase serotonin, at least at lower doses.

Laboratory animals were injected with the synthetic cannabinoid WIN55,212-2 and then tested with the Forced Swim test — a test to measure the equivalent of “depression” in animals. The researchers observed an antidepressant effect of cannabinoids paralleled by an increased activity in the neurons that produce serotonin. However, increasing the cannabinoid dose beyond a set point completely undid the benefits, said Dr. Gobbi.

“Low doses had a potent anti-depressant effect, but when we increased the dose, the serotonin in the rats’ brains actually dropped below the level of those in the control group. So we actually demonstrated a double effect: At low doses it increases serotonin, but at higher doses the effect is devastating, completely reversed.”

The anti-depressant and intoxicating effects of cannabis are due to its chemical similarity to natural substances in the brain known as “endo-cannabinoids,” which are released under conditions of high stress or pain, explained Dr. Gobbi.

They interact with the brain through structures called cannabinoid CB1 receptors. This study demonstrates for the first time that these receptors have a direct effect on the cells producing serotonin, which is a neurotransmitter that regulates the mood.

Dr. Gobbi and her colleagues were prompted to explore cannabis’ potential as an anti-depressant through anecdotal clinical evidence, she said.

“As a psychiatrist, I noticed that several of my patients suffering from depression used to smoke cannabis. And in the scientific literature, we had some evidence that people treated with cannabis for multiple sclerosis or AIDS showed a big improvement in mood disorders. But there were no laboratory studies demonstrating the anti-depressant mechanism of action of cannabis.”

Because controlling the dosage of natural cannabis is difficult – particularly when it is smoked in the form of marijuana joints – there are perils associated with using it directly as an anti-depressant.

“Excessive cannabis use in people with depression poses high risk of psychosis,” said Dr. Gobbi.

Instead, she and her colleagues are focusing their research on a new class of drugs which enhance the effects of the brain’s natural endo-cannabinoids.

“We know that it’s entirely possible to produce drugs which will enhance endo-cannabinoids for the treatment of pain, depression and anxiety,” she said.

Source: McGill University

Mixed Results With THC Antidepressants

Rick Nauert PhD

Rick Nauert, PhDDr. Rick Nauert has over 25 years experience in clinical, administrative and academic healthcare. He is currently an associate professor for Rocky Mountain University of Health Professionals doctoral program in health promotion and wellness. Dr. Nauert began his career as a clinical physical therapist and served as a regional manager for a publicly traded multidisciplinary rehabilitation agency for 12 years. He has masters degrees in health-fitness management and healthcare administration and a doctoral degree from The University of Texas at Austin focused on health care informatics, health administration, health education and health policy. His research efforts included the area of telehealth with a specialty in disease management.

APA Reference
Nauert PhD, R. (2015). Mixed Results With THC Antidepressants. Psych Central. Retrieved on August 20, 2018, from https://psychcentral.com/news/2007/10/24/mixed-results-with-thc-antidepressants/1447.html

 

Scientifically Reviewed
Last updated: 6 Oct 2015
Last reviewed: By John M. Grohol, Psy.D. on 6 Oct 2015
Published on PsychCentral.com. All rights reserved.