A PET study has revealed that emotional numbing symptoms of post-traumatic stress disorder (PTSD) are significantly linked to a receptor in the brain’s endocannabinoid system, a group at Yale University in New Haven, CT, has reported.
The finding is from a comparison of PET scans of the endocannabinoid system (ECS) among 62 individuals, including 46 trauma-exposed participants (19 with current PTSD) and 16 healthy controls, noted lead author Nachshon Korem, PhD, and colleagues.
“The ECS was linked to specific PTSD symptom expression, highlighting the potential for treatments targeting the ECS in mitigating these specific symptoms of this multi-faceted disorder,” the group wrote. The study was published August 22 in Translational Psychiatry.
PTSD is a debilitating psychiatric condition that arises following exposure to traumatic events. Evidence from animal studies suggests that the ECS plays a crucial role in the pathophysiology of PTSD partly through its cannabinoid receptors 1 (CB1R) and 2 (CB2R), the researchers explained. Specifically, CB1R are highly expressed in brain regions implicated in fear and stress responses, they noted.
To date, however, only a single study has investigated CB1R availability in humans exposed to trauma, and in this study, the researchers aimed to further explore potential connections.
The group analyzed data from 46 trauma-exposed participants and 16 healthy controls who had undergone PET scans at the U.S. Department of Veterans Affairs National Center for Posttraumatic Stress Disorder in West Haven, CT. Prior to the scans, patients received injections of carbon-11 (C-11) OMAR, a radiotracer developed in 2006 that binds with high affinity and selectivity to brain CB1 receptors.
According to the analysis, there were no differences in CB1R availability between the groups in either the whole brain or regions of interest. However, emotional numbing symptoms of PTSD were significantly linked to CB1R availability, the group noted.
“We found a robust association with the anhedonia symptom cluster of PTSD, where higher CB1R availability was associated with greater severity of anhedonia/emotional numbing (AN) symptoms,” the researchers wrote.
Further, the analysis found evidence for an interaction effect where women trauma controls showed higher C-11 OMAR levels compared to healthy men controls, although this finding requires replication in a larger sample, the group added.
The researchers noted that the only previous human study investigating the role of CB1R in trauma patients reported higher CB1R availability in PTSD subjects compared to healthy controls. Differences among the participants in the studies could account for the different findings, they wrote. For instance, the previous study’s participants included individuals who had experienced noncombat trauma, while the present sample predominantly consisted of veterans. Military-related trauma has been shown to uniquely impact symptom expression, cognitive functioning, and emotion regulation, all of which can influence outcomes and treatment responses, according to the group.
Ultimately, further research is warranted.
“Future research should aim to replicate these findings with greater female representation in the trauma-exposed control group, as well as a more detailed exploration of the interaction between trauma type and ECS function,” the researchers concluded.
The full study is available here.