Does cannabidiol reduce worry severity or anxiety symptoms? New placebo-controlled study says no

A study focusing on individuals highly prone to worrying revealed that a 300-milligram dose of cannabidiol (CBD) did not reduce the severity of their worry —  the cognitive symptoms of anxiety. This outcome was consistent with that of a placebo treatment, both after a single dose and following a two-week administration period. The study was published in Psychopharmacology.

Symptoms of anxiety can be classified into emotional, cognitive, physical, and behavioral manifestations. Emotionally, individuals with anxiety may experience feelings of unease, apprehension, or dread. On a cognitive level, persistent worry, racing thoughts, and difficulty concentrating are common symptoms. Physical symptoms include restlessness, muscle tension, fatigue, and disturbances in sleep patterns. Behaviorally, anxiety can lead to avoidance of certain situations, nervous habits, or seeking reassurance from others.

Standard treatments for anxiety include psychotherapy and medications. However, psychotherapy is expensive and not always easy to access, while existing medications have negative side effects such as sedation and weight gain. That is why researchers are looking for new convenient treatments for anxiety symptoms that are both accessible and free from negative side effects.

One promising candidate substance in this regard is cannabidiol. Cannabidiol is a chemical compound derived from the Cannabis sativa plant. Unlike tetrahydrocannabinol (THC), its counterpart, cannabidiol does not induce a psychoactive “high.” This has led to increased research interest in its potential therapeutic properties, including its anti-inflammatory, analgesic, and anxiolytic effects.

Study author L. Riley Gournay and colleagues aimed to investigate the effects of cannabidiol on symptoms of worry in individuals with a high tendency to worry. They compared the effects of a 300-milligram oral dose of cannabidiol, a 50-milligram dose of the same substance, and a placebo treatment, both immediately after the first dose and following two weeks of daily administration. They hypothesized that cannabidiol would reduce worry symptoms immediately after the first dose and that, after two weeks, participants taking cannabidiol would report lower worry levels compared to those receiving the placebo.

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The study included 63 participants with a high propensity for worry, as assessed using the Penn State Worry Questionnaire. The average age of the participants was 29 years, comprising 32 women, 30 men, and one individual identifying as gender non-conforming. The researchers specifically selected individuals with a high tendency to worry to avoid the ‘floor effect,’ where treatments cannot reduce worry in those who are not initially worried.

Participants were randomly assigned to one of three groups. Each group received either 150 milligrams of cannabidiol, 25 milligrams of cannabidiol, or a placebo, administered twice daily. This resulted in total daily doses of 300 mg of cannabidiol, 50 milligrams of cannabidiol, or a placebo, respectively. The treatments were administered in the form of six soft gel capsules, each containing either 25 milligrams of cannabidiol or inactive substances, to ensure uniformity in the number of capsules taken by each participant.

To verify adherence to the treatment protocol, participants recorded time-stamped videos of themselves consuming the capsules each time. Researchers advised them to eat a high-fat snack before taking the capsules to enhance absorption. The study was conducted in a double-blind manner, meaning neither the participants nor the researchers directly involved knew which treatment each participant was receiving.

Before the study, after the first day of the study and at the end of the study period, participants completed assessments of worry severity (the Brief Measure of Worry Severity) and anxiety symptoms (the anxiety scale of the Depression, Anxiety, and Stress Scales-21, DASS-21). After the study, they also completed a brief standardized interview about possible side effects of the treatment.

Results showed that levels of worry decreased during the study period on average. However, there were no significant differences between the three treatments. The average reductions in worry were similar for the 300 mg and 50 mg cannabidiol doses, and the placebo. The effects of the treatments were consistent both after the first day and after the entire two-week study period.

When examining overall anxiety symptoms, no differences were found between the three treatments after the first day. Yet, a comparison of anxiety symptoms at the end of the study revealed a decrease in physical symptoms in the cannabidiol groups, but not in the placebo group. This decrease was most pronounced in the group taking 300 milligrams of cannabidiol per day, and it was statistically significant, making the results generalizable beyond the sample.

“Taken together, these findings suggest 300mg of oral cannabidiol does not attenuate cognitive symptoms of anxiety (i.e., worry), following both acute and repeated administration. Some evidence for repeated administration of 300mg on physical symptoms of anxiety was obtained. These findings fit with accumulating evidence suggesting cannabidiols anxiolytic effects may be relevant to specific symptom domains,” the study authors concluded.

The study sheds light on the effects of cannabidiol on symptoms of anxiety. However, it should be noted that the study groups were very small. Because of this, effects had to be very substantial to be detected. If weak effects of the treatments were present, they could have remained undetected.

The paper, “The effects of cannabidiol on worry and anxiety among high trait worriers: a double‑blind, randomized placebo controlled trial”, was authored by L. Riley Gournay, Morgan L. Ferretti, Sarah Bilsky, Emily Vance, Anna Marie Nguyen, Eric Mann, Parker Williams, and Ellen W. Leen‑Feldner.