Two recent studies shed light on the biological mechanisms behind the therapeutic effect of cannabis for those suffering from PTSD. PTSD, or post-traumatic stress disorder, is a debilitating condition that causes chronic symptoms such as nightmares, panic attacks, hypervigilance, detachment from others, overwhelming emotions, and even self-destructive behavior in some cases. Despite inconclusive research on the topic, many PTSD patients continue to report that cannabis helps with their condition.

One study, conducted by researchers at Wayne State University in Detroit, MI, looked at how cannabis affects the amygdala response of those dealing with trauma-related anxiety, such as PTSD. The amygdala is a part of the brain associated with fear responses to threats. The study took three groups of participants - healthy controls without trauma exposure, trauma-exposed adults without PTSD, and trauma-exposed adults with PTSD - and randomly assigned them a low dose of THC or a placebo. Then, they were exposed to threatening stimuli and their amygdala responses were recorded. The results showed that those who took low doses of THC had lowered threat-related amygdala reactivity, meaning that they showed measurable signs of reduced fear and anxiety in situations designed to trigger fear. The results were found in all three groups, indicating that even those with PTSD were able to experience less fear with THC in their system.

Another study from researchers at Brazil's Federal University of Parana explored the possibility of cannabis helping to extinguish the intensity associated with traumatic memories in those with PTSD. This mode of treatment was first hypothesized by Yale associate professor of psychiatry R. Andrew Sewell who believed that cannabis could help PTSD patients overwrite traumatic memories with new memories through a process called "extinction learning." For those with PTSD, the normal extinction learning process doesn't happen, and the trauma attached to the old memories continues to cause problems. But, Sewell believed that cannabis could help by stimulating CB1 - a receptor in the endocannabinoid system that has improved extinction learning in animal studies - as those with PTSD show impaired functioning of the endocannabinoid system.

The recent study from Brazil's Federal University of Parana conducted a thorough review of the cannabis literature from 1974 to 2020, searching for evidence from controlled human trials to support or refute the theory that cannabis helps with the extinction of traumatic memories. The researchers found that low doses of THC or THC combined with CBD were both able to enhance the extinction rate for challenging memories and reduce overall anxiety responses. They concluded that the evidence from both healthy humans and PTSD patients suggests that these forms of cannabis "suppress anxiety and aversive memory expression without producing significant adverse effects."

These studies provide new insight into why cannabis helps PTSD sufferers feel better, both in the short-term and in the long-run. However, more research is needed to fully understand the effects of cannabis on PTSD and to determine the best ways to use it for therapeutic purposes.