Medical cannabis products are increasingly being used to treat conditions such as chronic pain and sleep disorders, yet evidence for the anti-depressant effects of weed remains somewhat patchy. However, a new small study in the journal Frontiers in Psychiatry has added some weight to the theory that the drug may help to treat depression, by revealing that users tend to display less severe symptoms than non-users.
Despite a lack of solid data regarding the impact of cannabis on depression, the study authors say that an increasing number of patients are now turning to the drug after failing to respond to conventional anti-depressants. To determine whether or not there is any benefit to doing so, the researchers recruited 538 participants who suffered from depression, anxiety or both.
Of these, 368 were already using medical cannabis to manage their symptoms, while the remaining 170 were considering doing so but had not yet begun self-treating with cannabis products. Participants were asked to complete an online survey that was designed to measure their levels of depression and anxiety, as well as their quality of life, chronic pain levels, and sleep issues.
Initial results revealed that medical cannabis users experienced less severe depressive symptoms than non-users, while also benefiting from greater quality of life, better sleep, and less pain. This was particularly true of participants using cannabis products that predominantly contained the non-psychoactive cannabinoid cannabidiol (CBD). Products dominated by tetrahydrocannabinol (THC), cannabis's psychoactive component, were not associated with improvements in depression.
“We found that use of THC-dominant products was not superior to use of non-THC-dominant products in alleviating depression symptoms,” write the authors. “In contrast, participants that reported use of CBD-dominant products provided significantly lower depression scores relative to those that did not.” They also note that no relationship was found between medical cannabis use and changes in anxiety levels.
Participants were invited to complete follow-up assessments every three months over the next four years, enabling the researchers to track their progress. During this period, a number of those who had been non-users at baseline began using medical cannabis, often leading to a noticeable improvement in their symptoms.
“We found that initiation of medicinal cannabis use was associated with a significant reduction in depressive symptoms, sustained use was associated with a modest reduction, and participants that did not use cannabis at all showed no difference in symptom expression between baseline and follow-up,” explain the researchers.
“These combined cross-sectional and longitudinal findings show a consistent antidepressant effect of medicinal cannabis.”
While these findings are highly encouraging, the authors point out that their study has numerous limitations. They acknowledge it is a very small study. The fact that it is merely an observational study and relies on self-reported questionnaires also makes it impossible to determine any causal relationship between cannabis use and reductions in depression.
The researchers therefore conclude that “future placebo-controlled studies are necessary to replicate these findings and to determine the route of administration, dose, and product formulation characteristics to optimize clinical outcomes.”