Metabotropic Glutamate Receptor 5 as a Potential Biomarker of the Intersection of Trauma and Cannabis Use

Abstract

Background: Metabotropic glutamate receptor 5 (mGlu5) dysregulation has been implicated in the pathophysiology of trauma-related psychopathology, and there are direct interactions between the endocannabinoid and glutamatergic systems. However, relationships between cannabis use (CU) and mGlu5 have not been directly investigated in trauma-related psychopathology. Methods: Using positron emission tomography with [18F]FPEB, we examined relationships between CU status and mGlu5 availability in vivo in a cross-diagnostic sample of individuals with trauma-related psychopathology (n=55). Specifically, we tested whether mGlu5 availability in frontolimbic regions of interest (ROIs; dorsolateral prefrontal cortex, orbitofrontal cortex, ventromedial prefrontal cortex, amygdala, hippocampus) differed as a function of CU status. Results: Past-year CU (n=22) was associated with 18.62%–19.12% higher mGlu5 availability in frontal and 14.24%–16.55% higher mGlu5 in limbic ROIs relative to participants with no recent CU. Similarly, past-month or monthly CU (n=16) was associated with higher mGlu5 availability in frontal (18.05%–20.62%) and limbic (15.53%–16.83%) ROIs. mGlu5 availability in the orbitofrontal cortex and amygdala was negatively associated with depressive symptoms in the past-year CU group. In both CU groups, exploratory analyses showed negative correlations between mGlu5 availability and sadness across all ROIs and with perceptions of worthlessness and past failures (r’s=−.47 to .66, P’s=.006–.033) in the ventromedial prefrontal cortex. Participants with CU reported lower mean depressive symptoms (P’s=.006–.037) relative to those without CU. Conclusions: These findings have substantial implications for our understanding of interactions between CU and glutamatergic neurotransmission in trauma-related psychopathology, underscoring the need for treatment development efforts to consider the effects of CU in this population.