The effects of cannabis use on emotion processing in depressed and non-depressed populations: an event related potential study

Background: The effects of Cannabis use on mood states, specifically emotion processing are unclear. Cannabis consumption has been related to self-medication for mood disorders such as depression, a growing trend in adolescent populations. The efficacy of this approach, both within a recreational or medical application is controversial, with negative and positive possible outcomes from cannabis exposure. Methods: Participants were scored as depressed using a cutoff of 16 on the CESD (Radloff,1977). A control group was compared to a self-reported cannabis users group. A total of 9 participants from 39 non users constituted a depressed sub-group, 11 from 27 a depressed sub-group of users. An Event related Potential Paradigm was then used to evaluate their ability to process female and male emotional facial expressions both explicitly and implicitly, as well as empathetically. Results: Cannabis users overall had decreased P1 and P3 compared to controls, with depressed users presenting the largest reduction in amplitude. Non-depressed controls presented increased P3 amplitude during empathic processing compared to the other tasks and to all users and depressed controls (F(6,372)=2.46; p<.05). In all users but not depressed controls this was accompanied by reduced P1 amplitude during empathetic processing most prevalent for angry faces (F(6,372)=2.76; p<.05). Conclusions: Cannabis use appears to modulate the processing of emotion in the brain. There are significant differences in the ERP’s of cannabis users compared to non-users for emotional stimuli. These effects are more marked in individual’s who are emotionally compromised. Further investigation is needed to clarify why these differences exist