Although Colorado recently declined to approve medical marijuana for the treatment of post-traumatic stress disorder (PTSD), a growing body of research shows a strong connection between the endocannabinoid system and PTSD.
PTSD involves a series of conditioned fear responses. In the words of Dr. Alexander Neumeister of the NYU School of Medicine, "\[PTSD\] is an illness where people cannot forget what they have experienced." Increasingly, it appears that the endocannabinoid system may play a large role in protecting against it. This may be due to both the number of cannabinoid receptors in the brain and the levels of cannabinoids present. PTSD sufferers tend to have more cannabinoid receptors than others, along with lower levels of at least one endocannabinoid.
A 2013 study published in the journal Psychoneuroendocrinology suggests that the role of the endocannabinoid system in protecting against PTSD may be critical. A joint effort between U.S. and Canadian researchers, the study examined 46 subjects who were in the vicinity of the World Trade Center during the 9/11 attacks. Of the participants, 24 suffered from PTSD while 22 did not. Researchers discovered that those who experienced PTSD symptoms also had lower concentrations of anandamide -- one of the body's naturally-occurring cannabinoids -- than those without PTSD.
The cannabinoid receptors concentrated in the brain and nervous system that mediate many functions, including emotional learning and adaptation to stress, are called CB1 receptors. They're also involved in fear extinction, which is defined as a decline in conditioned fear responses. When the brain experiences deficits in cannabinoids, this can interfere with CB1 signaling. Improper CB1 signaling can result in the hallmark symptoms of PTSD, including impaired fear extinction, poor memory consolidation, and chronic anxiety.
Further research, including a 2013 study conducted at the NYU Langone Medical Center, supports this idea. The study, published in Molecular Psychiatry, used positron emission tomography to look at the brains of subjects with PTSD and without. The study included 60 people, and found that not only did subjects with PTSD have lower anandamide, they also had more CB1 receptors in the areas of the brain associated with fear and anxiety. This suggests that using cannabis to increase cannabinoid levels may be an effective tool for the treatment of PTSD.