In the US, the state of New Mexico was the first to legalize the use of medical cannabis for people with PTSD. The requirement is that a psychiatrist certified that the benefits would outweigh the health risks. This paper covers both a study on humans and some supplementary evidence covering animal model studies.
In the trials, there was a 75% reduction in PTSD symptoms. This response was specifically in the areas reexperiencing, avoidance, and hyperarousal. Reexperiencing is the term used to cover things such as flashbacks, where the past trauma comes back to the present. Avoidance can be both avoiding specific behaviors, or avoiding emotions. Hyperarousal is the increase in anxiety and altered emotional responses.
Here is the full scientific article if you wish to download it.
The authors warn that because a lot of the participants in the study were those that already found that cannabis reduced their PTSD symptoms. This means the results don’t represent the real population of people with PTSD. For some people, medical cannabis may have no effect. Additionally, some participants may have joined the program to escape criminal penalties, and therefore may be inclined to overstate the effectiveness. For these reasons, a more comparative study that would provide more reliable results is needed.
In animal models of PTSD, medical cannabis was found to produce positive results. Animal models are chosen for their close similarity to human cases of PTSD, in which medicines would usually produce the same results in humans. These trials are strictly controlled by ethics boards. In these studies, cannabinoids from medical cannabis reduced symptoms of PTSD, including a reduction in conditioned fear.