A study in Canada found that a single oral dose of cannabidiol has no effect on fear and panic symptoms experienced during a 5-minute exposure to air with 10% carbon dioxide (CO2). There was no effect on heart rate either. The research was published in Psychopharmacology.
Cannabidiol is a naturally occurring chemical compound found in the cannabis plant. Unlike tetrahydrocannabinol (THC), the other major component of cannabis, cannabidiol is not psychoactive, meaning it does not cause a “high.” It is typically extracted from hemp, a variety of cannabis that contains very low levels of THC.
Cannabidiol interacts with the body’s endocannabinoid system, which helps regulate functions such as mood, sleep, pain, and appetite. Research suggests cannabidiol can help reduce anxiety, improve sleep, and alleviate certain types of chronic pain. In medical contexts, cannabidiol has been approved in some countries as a treatment for rare forms of epilepsy. It is distributed in the form of oil, capsules, edibles, or topical cream. Cannabidiol is generally not considered an illicit substance if derived from hemp with very low THC, but its legality varies by country and local regulations.
Study author Ellen W. Leen-Feldner and her colleagues note that previous studies showed that a single administration of cannabidiol can reduce anxiety in situations that induce social anxiety. They wanted to see whether cannabidiol administration could also reduce fear.
To do this, they designed a study in which they induced fear by exposing participants to air enriched with 10% carbon dioxide, a situation known to cause fear and even panic. This concentration of carbon dioxide in the air induces a feeling of suffocation and being unable to breathe. That feeling triggers strong fear and an innate panic response. This is a survival reflex that bypasses rational thought.
Study participants were 84 adults with an average age of 26 years. They were required to be in good physical and mental health, to not have recently used anxiolytic medication, cannabidiol, or THC, and to have no prior experience with carbon dioxide–enriched air administration.
Participants were divided into four groups. Three groups differed in the dose of cannabidiol they received: 150 mg, 300 mg, or 600 mg. The fourth group was a placebo group that did not receive cannabidiol (but believed it did). Participants received softgel capsules that either contained 50 mg of cannabidiol in medium-chain triglyceride oil each (active treatment capsules) or just the oil with no cannabidiol (placebo capsules).
Each participant received 12 capsules, but groups differed in how many of the capsules contained cannabidiol. For participants in the 600 mg group, all 12 capsules were active capsules. For the 300 mg group, 6 capsules contained cannabidiol and 6 did not. The placebo group received only capsules with no cannabidiol. Participants were not aware of the group they were in.
After taking their assigned capsules, participants breathed air enriched with 10% carbon dioxide through a breathing mask with continuous positive airway pressure for 5 minutes. Before and during the procedure, the researchers monitored participants’ heart rate. Participants continuously rated their own sensations of fear starting 30 seconds before breathing carbon dioxide–enriched air and continuing until 60 minutes after they stopped. They also completed an assessment of panic experiences by rating how strongly they felt 13 different panic symptoms (the Diagnostic Sensations Questionnaire).
As expected, results showed that breathing carbon dioxide–enriched air induced fear. However, none of the cannabidiol groups differed from the placebo group in the level of fear or panic they experienced. Heart rate changes also did not differ between groups.
“Taken together, the current study provides the first evidence suggesting CBD [cannabidiol] does not meaningfully reduce fear in humans,” the study authors concluded.
The study demonstrated that cannabidiol has no effect on fear. This does not contradict the previous findings about cannabidiol reducing anxiety because anxiety and fear are physiologically distinct emotions. Previous studies clearly demonstrated that they are affected by different emotions.
However, it should be noted that the number of participants per treatment group in this study was very small. This means that fear reducing effects needed to be very strong to be detectable using the statistical procedures study authors employed. Results of studies on larger groups might differ in that they might be able to detect weaker effects.
The paper, “A double‑blind, randomized, placebo‑controlled test of the effects of cannabidiol on fear elicited by a 10% carbon dioxide‑enriched air breathing challenge,” was authored by Ellen W. Leen‑Feldner, Teah‑Marie Bynion, Graham M. L. Eglit, Marcel O. Bonn‑Miller, L. Riley Gournay, and Matthew T. Feldner.
