PULLMAN, Wash. — Cannabis is often used as a stress reliever, but a new study suggests that some of the body’s stress response systems don’t get the message.
A human trial of regular cannabis users found that cannabis use lowered some physiological stress measures, such as cortisol levels, but others remained unaffected or increased after vaping cannabis. Notably, cannabis use corresponded with a faster heart rate and had no effect on heart rate variability, a key measure of stress response. The study, published in the journal Neuropsychopharmacology, was led by Washington State University researchers.
Across all measures, the strongest evidence of stress relief came from the subjective reports of participants, who consistently reported feeling less stress — whether they vaped a little THC, a lot of THC or a placebo.
“One measure of stress is just to ask people: How stressed do you feel right now? Interestingly, that often doesn’t actually map onto physiological indicators of stress that we measure,” said study lead author Carrie Cuttler, an associate professor of psychology who directs The Health and Cognition (THC) Lab at WSU.
“Consumers should understand that while they feel like cannabis is reducing their stress, that could largely be a kind of placebo effect, due to their expectations of what they think cannabis is going to do.”
Stress takes many forms — emotional, physical and behavioral. It shows up as a feeling or subjective response. It produces higher levels of some hormones, speeds up the heart, reduces heart rate variability, and raises blood pressure. When the nervous system is aroused, sweat glands in the skin are activated, raising the electrical conductivity of the skin.
Cannabis users consistently report using the drug to reduce stress, but there has been little research into whether their beliefs are borne out across multiple physiological responses.
The WSU researchers conducted a randomized, double-blind, placebo-controlled trial in which 120 regular cannabis users inhaled a placebo, a 20-milligram dose of THC or a 40-milligram dose of THC. They were evaluated on several stress measures five minutes after vaping and again an hour after vaping.
Participants in all groups reported significantly less stress at both time points, which suggests the effects were based on their expectations rather than the drug. The researchers concluded there was no evidence that cannabis reduced subjective stress more than the placebo. The placebo effect was so pronounced that in one case, a study subject in the placebo group “tapped out” – stopped inhaling because they felt the effects were too strong.
“Placebo effects are really, really powerful,” Cuttler said. “That’s why it was so important to have a placebo control condition in this study.”
In addition, researchers measured four physiological responses: cortisol levels, heart rate, heart rate variability and the electrical conductivity of the skin.
Cortisol levels dropped significantly among those who vaped THC versus the placebo, though those levels rebounded relatively quickly. The magnitude of the skin conductance response was also lowered among THC users, which reflects a lower nervous system arousal.
On the other hand, subjects who vaped THC showed an increased heart rate, with a significant increase in the high-dose THC group versus the placebo. The researchers found no significant difference in heart rate variability.
“Finally, we found that these different indicators of stress didn’t correlate with each other,” Cuttler said. “Changes in cortisol were completely unrelated to changes in subjective stress. Changes in cortisol were completely unrelated to heart rate. It was completely unrelated to electrodermal activity. Changes in electrodermal activity were not related to changes in heart rate, heart rate variability, or subjective stress, suggesting that these things are affected differently by cannabis.
“It’s not a consistent story. Cannabis has different effects depending on the outcome that you’re looking at.”
Co-authors of the study included Ryan J. McLaughlin, an associate professor in the WSU Department of Integrative Physiology and Neuroscience and Cuttler’s co-principal investigator; Matteya A. Proctor, a PhD student in neuroscience; Zachary D. G. Fisher, a research technician; Nicholas C. Glodosky, a graduate research assistant; and researchers from Arizona State University.
Media Contacts
- Carrie Cuttler, WSU Department of Psychology, 509-335-0681, carrie.cuttler@wsu.edu
- Shawn Vestal, WSU News & Media Relations, shawn.vestal@wsu.edu
