Preventing PTSD-like symptoms (post-traumatic stress disorder) in rats caused by trauma or trauma reminders has been possible when rats took marijuana soon after a traumatic event.
The importance of this study is that it contributes to the understanding of the brain basis of the positive effect cannabis has on PTSD and thus supports the necessity to perform human trials to examine potential ways to prevent the development of PTSD and anxiety disorders in response to a traumatic event.
The study by Nachshon Korem and Irit Akirav of the Department of Psychology at the University of Haifa suggests that approximately nine percent of the population suffers from post-traumatic stress disorder, whereas among at-risk populations such as combat soldiers, prisoners, victims of assault, citizens in lines of confrontation, etc., the percentages are even higher.
A common phenomenon among those who suffer from trauma is that exposure to a "trauma reminder" - an event that is not traumatic in essence but that evokes the memory of the experience of the traumatic event - can further heighten the negative effects of the trauma. For example, for a person who has developed post-traumatic syndromes as a result of "Color Red" sirens (air raid sirens), a trauma reminder can occur following a loud car alarm.
From the findings it became clear that the rats that were injected with the cannabinoid substance showed no PTSD symptoms such as impaired extinction learning, increased startle response, changes in sensitivity to pain and impaired plasticity in the brain's reward center (the nucleus accumbens), compared to those not injected with the drug. The researchers added that the rats that were injected with the drug showed better results compared to rats who received sertraline (an antidepressant of the SSRI group) a substance that is used in the treatment of PTSD with limited success in reducing symptoms.
In fact, for some of the symptoms, the rats that were injected with the drug showed similar behavior to rats exposed to trauma but that were not exposed to trauma reminders. In other words - cannabis made the effects of trauma reminders "disappear".
The study aimed to examine the neurobiological basis for the improvement caused by the drug. It was found that rats who were exposed to trauma and to trauma reminders showed an increase in the expression of two receptors in the brain associated with emotional processing: the CB1 receptor, a receptor in the brain that cannabinoids are known to bind to, and receptor GR, the receptor associated with exposure to stress. On the other hand, in rats that received cannabinoids, the increase in the expression of these two receptors was prevented in the hippocampus and prefrontal cortex, areas involved in forming and saving traumatic memories.
The study was published in the journal Neuropsychopharmacology.