Emotion processing differences in current and past users of cannabis

Cannabis abuse and addiction is associated with detrimental effects on cognition and behavior. Recent neuroimaging research suggests that casual users present morphological differences in brain areas associated with emotion processing; it is unclear whether these differences are reflected in cognitive, behavioral, and functional measures. We examined event-related brain potentials (ERPs) in current and past cannabis users and non-users during emotion processing. Electroencephalogram was recorded while participants viewed images of male and female faces depicting happy, angry, fearful, and neutral emotional expressions. Participants completed three tasks in which they identified the sex or the emotion for all faces, or empathized with the emotion depicted by each image (implicit, explicit, and empathic conditions, respectively). Current and past users presented differences in ERP components during emotion processing. Specifically, users presented with decreased ERPs overall, but especially in P1 amplitude over parietoccipital electrodes and to P3 amplitude overparietal and frontal medial sites. This P3 attenuation in current users was most noticeable during empathic processing, in which participants were instructed to empathize with the emotion depicted as they would for a close friend or relative. This data supports a relationship between cannabis use and changes of affective systems in the brain. Further study will assess a larger population of users that will allow us to examine in more detail the relationship between levels of use and altered emotion processing as measured by electrophysiological and behavioral measures.