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Medical Cannabis Use May Reduce Anxiety and Depressive Symptoms, Study Finds

By Alexander Beadle

Published: Oct 26, 2021   
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Medical cannabis can reduce anxiety and depression, according to a new study from Johns Hopkins University and the non-profit Realm of Caring Foundation.

Longer-term medical cannabis users reported lower levels of depressive symptoms, as well as superior sleep, quality of life, and less pain on average compared to a control group of non-cannabis users with similar health conditions.

In light of these findings, the researchers believe that future placebo-controlled trials are needed in order to determine the ideal dosages and product formulations of medical cannabis that would optimize clinical outcomes for patients with depression and anxiety.

Medical cannabis use associated with reduced depressive symptoms

Participants were recruited for the study via social media and directly from the Realm of Caring Foundation’s patient registry between April 2016 and July 2020. In total, 368 cannabis consumers were registered at the baseline of the study along with 170 non-cannabis users (but who were considering future use).

Each of the study participants was asked to fill in an online questionnaire to assess their general health and their cannabis usage. This questionnaire included an evaluation of current anxiety and depressive symptoms using the Hospital Anxiety and Depression Scale (HADS), which categorizes clinical depression with a score of more than eight. An abbreviated version of the World Health Organization Quality of Life assessment (WHOQOL-BREF) was also included, as well as other standardized assessments to measure sleep quality and past-month pain.

At baseline, the cannabis consumers reported lower levels of depression according to the HADS assessment and were more likely to present below the HADS cut-off for clinical concern. However, there were no significant differences in self-reported anxiety levels between the cannabis-using and control groups.

The cannabis users at baseline also reported better past-month sleep quality, higher quality of life, greater health satisfaction, and had higher psychological domain scores on the WHOQOL-BREF compared to the non-users. Given the higher incidence of participants with co-occurring chronic pain, it is also interesting to note that the medical cannabis users reported lower past-month average pain levels – consistent with other real-world research and expert recommendations suggesting medical cannabis can relieve chronic pain.

Anxiety and depression reduced after beginning medical cannabis use

The study participants also had the option to take part in follow-up assessments which were offered every three months for longitudinal analysis. During the course of these follow-up assessments, 36 of the control group participants followed through on their intention to initiate medical cannabis use. The data recorded from these patients during the follow-up allowed the researchers to also examine the initial effects of beginning medical cannabis use.

This group reported significant reductions in both their depression and anxiety symptoms after initiating cannabis use. A similar, but smaller effect was also seen in participants from the original cannabis user group who sustained their cannabis use throughout the entire course of the trial, suggesting that both the onset of cannabis use and extended use can provide some benefit to anxiety and depression.

The researchers note several limitations on this study. Firstly, the fact that it relied on participant self-reporting meant that there was a possibility of an expectancy effect leading cannabis users to attribute symptom improvement to their use of cannabis, rather than other factors. This might have also affected the members of the control group who later began using cannabis.

Additionally, dosing data could only be calculated for around half of the study participants due to the poor labeling of some retail and all black market cannabis products. While the majority of participants reported using CBD-dominant products, the exact makeup of many products could not be confirmed. Dosing information is important as high-potency cannabis products have been previously linked to poor mental health outcomes, so assessing the THC content of the products being used by persons with anxiety and depression would provide an interesting extra dimension for further study.

Notably, the documented CBD doses used in this study did appear to be significantly lower on average than the doses used in trials investigating CBD and mental health, suggesting that CBD may be effective in much lower doses than previously thought.

“The biggest misconception this study addresses is that CBD doses need to be between 400-600 mg before positive psychiatric effects can be achieved,” Dr Nicolas Schlienz, research director for Realm of Caring, said in a statement. “We observed positive effects in people taking an average of only about 60 mg per day, 1/10th of that dose.”

In light of these findings, the researchers feel that placebo-controlled trials are needed in order to properly confirm the effectiveness of low-dose CBD for improving mental health and to gauge whether the effectiveness of medical cannabis products may be gated by their duration of use.


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