A longitudinal study published in Frontiers in Psychiatry investigated the effects of medicinal cannabis among clinically depressed and/or anxious patients. Those who were using medicinal cannabis at baseline had lower depression scores than non-users, and non-users who began taking cannabis during the follow-up period experienced a reduction in both anxiety and depression symptoms.
Anxiety and depression are of the most common mental health conditions around the world. While there are existing therapeutic and pharmacological treatments, evidence suggests that many sufferers fail to seek help and are wary of the side effects of taking medication.
Study authors Erin L. Martin and her colleagues note that many people with anxiety and depression are turning to medicinal cannabis as a way to manage their symptoms. These products can be made predominantly of tetrahydrocannabinol (THC), cannabidiol (CBD), or equal amounts of both. Studies investigating the therapeutic effects of these products have shown promise but have yielded mixed results, and the ideal dosage remains unclear.
“Anxiety and depressive disorders are highly prevalent. Traditional antidepressants may effectively treat these disorders in a lot of people, but they do not work for everyone and can have unpleasant side effects,” explained Martin, a PhD candidate at the Medical University of South Carolina.
“People are increasingly using medicinal cannabis products, especially products high in CBD, to try to treat symptoms of anxiety and depression, even though scientific research in this area is both limited and shows mixed results.”
“We conducted this study to determine if people that used medicinal cannabis products to treat symptoms of anxiety and depression reported improvement in these symptoms, as well as in other important areas like sleep and quality of life, relative to people that did not use medicinal cannabis.”
Martin and her team conducted a study among a sample of participants who reported having anxiety, depression, or both. Importantly, 368 participants were medicinal cannabis users, and 170 were considering using medicinal cannabis but had not yet begun using it. The majority of respondents were female (79%) and Caucasian (83%).
At a baseline assessment, the participants answered questions about their cannabis use and completed assessments of anxiety, depression, recent pain, quality of life, and sleep quality. Every three months over a period of roughly four years, the participants were invited to complete a follow-up assessment. On average, participants completed two assessments.
At baseline, 34% reported having anxiety, 15% reported having depression, and 51% reported having both. Additionally, 69% reported having a chronic pain disorder. About 36% said they were using serotonergic medication to manage their depression and/or anxiety. Among cannabis users, CBD-dominant products were by far the most commonly used cannabis product, with such products being used by 82% of users.
Just under one-quarter of respondents (23%) said they used THC-dominant products, 7% said they used products with an equal balance of THC and CBD, and 5% used products dominated by a minor cannabinoid.
At baseline, cannabis users reported lower levels of depression compared to nonusers, especially if they were using CBD-dominant products. Cannabis users also reported a higher quality of life, better sleep in the past month, less pain in the past month, and were more likely to demonstrate depression symptoms that were below clinical concern. Levels of anxiety did not differ between cannabis users and nonusers at baseline.
Interestingly, people who were not using medicinal cannabis at baseline but began using during the follow-up period demonstrated reductions in both anxiety and depression. They also showed improvements in the psychological domain scores on a shortened version of the World Health Organization Quality Of Life assessment. People who were using cannabis at baseline and continued to use also showed reductions in anxiety and depression, but to a lesser extent than new users.
“Medicinal cannabis products, especially products high in CBD, may help to treat symptoms of depression, improve sleep, and increase quality of life,” Martin told PsyPost. “There is also some evidence that medicinal cannabis may alleviate symptoms of anxiety, particularly if administered over an extended period of time, but this is less clear from our results and warrants further study.”
Martin and her colleagues offer a few reasons why CBD may have been associated with reductions in anxiety in the long-term, but not at baseline. It could be that those who reported using cannabis products at baseline had developed a tolerance to its anxiety-reducing effects. Alternatively, it could be that the clinical effects of CBD on anxiety are only observed after a certain time lag — speculation that could be explored with repeated sampling methods like ecological momentary assessment.
The study authors acknowledge their findings are limited since they relied on participant self-reports, and they cannot rule out expectancy effects. They say that future studies using a placebo-controlled design will be needed to further explore the potential anxiety-alleviating and antidepressant effects of CBD and to shed light on optimal dosages.
“This is an observational study in a convenience sample, so it is possible that the results we observed could be partially attributable to a placebo effect or to people being more likely to complete the study if they found medicinal cannabis products effectively treated their symptoms,” Martin explained.
“Randomized, placebo-controlled trials on the antidepressant and anxiolytic effects of medicinal cannabis are needed. Furthermore, it is still unknown how people should be dosing medicinal cannabis products in order to achieve the best effect (How much? How long? What cannabinoid content?) This should also be explored in future research.”
“We would like to thank the Realm of Caring Foundation and the National Institute on Drug Abuse (NIDA) for providing support for this research,” she added.
The study, “Antidepressant and Anxiolytic Effects of Medicinal Cannabis Use in an Observational Trial”, was authored by Erin L. Martin, Justin C. Strickland, Nicolas J. Schlienz, Joel Munson, Heather Jackson, Marcel O. Bonn-Miller, and Ryan Vandrey.
