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Post-Traumatic Stress Disorder

Veterans, PTSD, and Cannabis

Cannabis is popular PTSD treatment among vets, but side effects can be harmful.

Key points

  • Conventional wisdom among many veterans with PTSD is that cannabis is the best treatment, but the VA cannot recommend or provide cannabis.
  • There is good evidence that THC reduces nightmares and intrusive re-experience of trauma reactions in combat veterans.
  • Continuous use of cannabis, even for its beneficial effect on PTSD, can have the side effect of addiction and reduction of its benefits.
  • More effective medications with fewer side effects are under development to increase the brain's natural cannabinoid chemistry.

The Mayo Clinic defines PTSD as a mental health condition triggered by either experiencing or witnessing a terrifying event.(1) While it is natural to have temporary difficulties as the result of such an event, PTSD exists when flashbacks, nightmares, severe anxiety, and intrusive thoughts about the event persist for months or even years.

As PTSD sufferers alternate between being overwhelmed and flooded with emotion or being numb and unfeeling, a variety of symptoms interfere with their lives, including depression, hyperarousal, memory and concentration impairment, sleep disturbances, digestive problems, headaches, and hypertension. Approximately 7-8% of American adults experience PTSD during their lifetime, with women suffering twice as often as men.

The prototypic PTSD sufferer is a combat veteran, although this does not do justice to the rate and severity of PTSD suffered by victims of domestic violence and sexual abuse. A focus on veterans is particularly relevant to any discussion about medical cannabis because of the popularity of cannabis use among veterans and the number of studies analyzing cannabis use for their PTSD. Because the federal government prohibits cannabis for any use, VA hospitals cannot recommend or provide cannabis, even in states that have legalized medical marijuana. As a result, several veteran organizations advocating medical cannabis have sprung up, including Weed for Warriors. Even as I write this paragraph, I have received an invitation to a cannabis information conference sponsored by the Veterans Cannabis Group.

Understanding the stress response

To understand why so many veterans with PTSD experience benefit from cannabis, and some of the limitations to this benefit, a few basic elements of the stress response must be understood.

When danger threatens, the amygdala sends signals to initiate our fight-or-flight response. A body in fight-or-flight mode directs maximum blood flow and energy to muscles and shuts down unnecessary functions such as digestion. The amygdala accomplishes all this by activating the sympathetic nervous system and initiating a cascade of stress hormones.

Although the steps in this process are complex, the outcome is plain. Heart rate increases and adrenal glands pump adrenalin into the bloodstream. This all occurs so fast that we can startle and develop clammy hands even before being conscious of the danger threatening us.

The adrenal glands also secrete the master stress hormone, cortisol. Cortisol raises blood sugar for maximum energy and prepares the body to heal any injuries.

The whole stress response is normally self-limiting. A sudden fear that we forgot to mail our income tax return on time can activate the fight-or-flight response, with all its hormonal consequences. But once we remember it was mailed yesterday, the neural and hormonal stress response quickly fades. However, when our stress response is as intense and continuous as it is in combat situations, it overwhelms normal self-limiting influences. Under these conditions, PTSD can develop. Once PTSD sets in, the full stress response continues to recur in reaction to even small reminders of the original trauma.

The effects of cannabis on PTSD

In a person suffering from PTSD, the amygdala remains hyperactive, ready to trigger fight or flight at a moment’s notice, even when momentary circumstances only vaguely resemble the original trauma. Scientific research has clearly shown a dose of THC quickly suppresses neural activity in the amygdala. As cannabis is experienced as an unmistakable benefit by most PTSD sufferers, it has become accepted wisdom that cannabis treats PTSD.

In addition, research also shows the process of forgetting painful memories is controlled by the brain’s natural cannabinoid chemistry. When rats are trained to seek shelter whenever a bell rings to signal an incoming electric shock to the floor of their cage, and then the shock stops following the bell, researchers measured how long it takes for rats to stop reacting to the bell. When given THC, the rats stop their fearful reaction to the bell sooner than those not given THC. When given a drug that blocks cannabinoid receptors, rats take much longer to stop fearing the bell.(2) Our natural cannabinoid chemistry reduces our reaction to reminders of painful events, converting painful experiences into memories rather than allowing them to be re-experienced over and over. Unsurprisingly, veterans experience fewer intrusive, painful re-enactments of past trauma when they use cannabis.

The Trauma and Stress Support Centres run by the Canadian Armed Forces Mental Health Services gave a synthetic cannabinoid similar to THC (nabilone) to veterans with PTSD who were still having nightmares after conventional drug treatment.(3) A remarkable 72% experienced less intense or complete cessation of nightmares. Unfortunately, the Centres did not control their study with a placebo, so the improvement could have been due to an infusion of hope brought by starting a new drug treatment. The power of a placebo to instill hope should never be underestimated. A similar study conducted 5 years later in New Mexico, also marred by the lack of a control group, found a 75% improvement in PTSD symptoms in veterans treated with medical marijuana.(4)

Potential side effects of cannabis use for PTSD

All medications have potential side effects and cannabis use for PTSD is no exception. Cannabis addiction is a potential side effect with real-life consequences (see previous posts "5 Signs of Using Cannabis Too Frequently" and "How Cannabis Defeats Itself When Used Too Frequently"). According to the National Center for PTSD, more than 40,000 veterans were seen by the Department of Veterans Affairs in 2014 with both PTSD and cannabis addiction.(5)

When people with cannabis addiction reduce or stop their cannabis use, amygdala activity rebounds above normal levels for a while, which increases PTSD symptoms. Fortunately, there are ways to quell the amygdala without using THC. For example, some drugs under development have been shown to reduce the breakdown of our natural cannabinoid chemistry, which reduces activity in the amygdala without THC’s side effects, including addiction.

Even with an effective, non-psychoactive alternative available, not all PTSD sufferers would be willing to abandon cannabis. The seductive high from cannabis, with its emotional numbing, is likely to continue making cannabis the drug of choice for many.



2. Marsicano, et al. The Endogenous Cannabinoid System Controls Extinction of Aversive Memories. Nature, 2002; 418: 530–4.

3. G. A. Fraser. The Use of a Synthetic Cannabinoid in the Management of Treatment-Resistant Nightmares in Posttraumatic Stress Disorder (PTSD). CNS Neurosci Ther, 2009; 15(1): 84–8.

4. G. R. Greer, et al. PTSD Symptom Reports of Patients Evaluated for the New Mexico Medical Cannabis Program. J Psychoactive Drugs, 2014; 46(1): 73–7.

5. M. O. Bonn-Miller and G. S. Rousseau. Marijuana Use and PTSD among Veterans. PTSD: National Center for PTSD, U.S. Department of Veterans Affairs. (Accessed March 26, 2019.)