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More study needed on possible role of pot in psychotherapy

The jury is still out on use of cannabis to treat PTSD and anxiety disorders.

by David Valentiner, Ph.D., and Sara Wyman, guest contributors

In many states, pot use is being legalized for medical purposes, but the jury is still out on the case for or against the use of cannabis in the treatment of anxiety and post-traumatic stress disorders.

Those disorders are experienced by more than one in six people in the United States (Kessler, Chiu, Demler, & Walters, 2005).

The immediate effects of marijuana differ from person to person and situation to situation. Many people report feeling less anxious after smoking marijuana, but others actually report feeling more anxious. Apart from the immediate effects, we might ask whether marijuana has any long-term impact on anxiety.

A few scientists have suggested that marijuana use leads to lasting reductions in anxiety symptoms (Greer, Grob, & Halberstadt, 2014). If this were the case, you’d expect to see a low percentage of marijuana users suffering from anxiety disorders or PTSD -- why would their problems persist if they smoke regularly?

However, rates of cannabis use are not lower among individuals with anxiety disorders, and are, in fact, higher among individuals with PTSD (Kessler et al., 2005). So cannabis use alone does not appear to lead to long-term recovery from anxiety disorders or PTSD. Still, a variety of studies, mostly with mice, suggests that cannabis might play some treatment role.

Let’s first consider how cannabis affects the brain, and what happens in the brain during treatment for anxiety disorders and PTSD.

Healthy brains produce cannabinoid molecules as part of normal functioning. These cannabinoids are a type of neurotransmitter, which are chemicals needed for communication between brain cells, called neurons. Introducing externally produced cannabinoids into the brain through smoking marijuana stimulates neuronal action in those parts of the brain where cannabinoid receptors, or detectors, are located.

Marijuana has effects on many areas of the brain because these receptors are found throughout. One area is the hippocampus, which is particularly important to anxiety disorders and PTSD because of the role it plays in learning and memory. The way that cannabinoids affect the hippocampus has led some researchers to speculate that, under some conditions, cannabis might promote learning processes related to danger and safety (Wilson & Nicoll, 2002).

Psychotherapy for anxiety disorders and PTSD is highly effective (Hofmann & Smits, 2008). It involves something known as safety learning, which helps people overcome unreasonable fears or anxiety and, like marijuana use, also involves the hippocampus.

Safety learning requires, among other things, a person to confront the objects or situations that he or she fears, but these confrontations must be carefully controlled to avoid further “danger learning” and a worsening of symptoms. Psychotherapy for anxiety disorders and PTSD works best when the therapist creates conditions that help clients to reevaluate their feared objects and situations in ways that lead to safety learning.

So could cannabis help amplify the safety-learning process? Some other chemicals have been found to amplify the effectiveness of therapy sessions. For example, d-Cycloserine and Methylene Blue have been shown to make exposure therapy for anxiety disorders more effective (Hofmann, Smits, Asnaani, Gutner, & Otto, 2011). The fact that other chemicals can promote safety learning suggests that there may be a role for cannabis.

But as we have learned, cannabis can be a double-edged sword. If cannabis is found to promote safety learning, it would also be expected to promote danger learning. Cannabis, like d-Cycloserine and Methylene Blue, might act synergistically to make good therapy better, but it might also make bad therapy worse.

OK, now back to the mice. To date, several studies have found that cannabinoids increase safety learning in animals. One similar study with humans examined safety learning, but the test subjects were not experiencing anxiety disorder or PTSD. There have not been any of the controlled clinical trials that would be needed for scientific certainty.

As scientists move forward with studies to determine whether or how cannabis can help therapy for anxiety disorders and PTSD, other questions must to be addressed.

Both animal studies and studies with other chemicals suggest that regular use of cannabis will likely interfere with any beneficial effects, so people who use marijuana regularly will probably not experience any additional benefit. And it is still not known what may be the optimal dose or way to administer cannabis to help psychotherapy.

Finally, little is known about the effect of marijuana use on the natural course of anxiety disorders and PTSD. Scientists do not yet understand how smoking pot is related to natural recovery and persistence of these conditions.

The apparent role of cannabinoids in danger and safety learning points to new and exciting questions for researchers. But the complexity of human-learning processes suggests that a good deal more research is needed to clarify the potential role of cannabis in treating anxiety disorders and PTSD.

David Valentiner, Ph.D., is a professor of psychology at Northern Illinois University. His research focuses on cognitive, emotional, and interpersonal processes related to anxiety and anxiety disorders, including social anxiety, posttraumatic stress disorders, and panic disorder.

Sara Wyman is a graduate student in the clinical psychology program at Northern Illinois University. She researches personality, and the role of beliefs and cognitions in the development, maintenance, and treatment of obsessive-compulsive disorder.


Greer, G. R., Grob, C. S., & Halberstadt, A. L. (2014). PTSD Symptom Reports of Patients Evaluated for the New Mexico Medical Cannabis Program. Journal of Psychoactive Drugs, 46(1), 73-77.

Hofmann, S. G., & Smits, J. A. (2008). Cognitive-behavioral therapy for adult anxiety disorders: a meta-analysis of randomized placebo-controlled trials. The Journal of clinical psychiatry, 69(4), 621.

Hofmann, S. G., Smits, J. A., Asnaani, A., Gutner, C. A., & Otto, M. W. (2011). Cognitive enhancers for anxiety disorders. Pharmacology Biochemistry and Behavior, 99(2), 275-284.

Kessler, R.C., Chiu, W.T., Demler, O., & Walters, E.E. (2005). Prevalence, severity, and comorbidity of twelve-month DSM-IV disorders in the National Comorbidity Survey Replication (NCS-R). Archives of General Psychiatry, 62, 617-27.

Wilson, R. L., & Nicoll, R. A. (2002). Endocannabinoid signaling in the brain. Science, 296, 678-682.