Do reward-processing deficits in schizophreniaspectrum disorders promote cannabis use? An investigation of physiological response to natural rewards and drug cues

Background: dysfunctional reward processing is present in individuals with schizophrenia-spectrum disorders (ssd) and may confer vulnerability to addiction. our objective was to identify a deficit in patients with ssd on response to rewarding stimuli and determine whether this deficit predicts cannabis use. methods: we divided a group of patients with ssd and nonpsychotic controls into cannabis users and nonusers. response to emotional and cannabis-associated visual stimuli was assessed using self-report,event-related potentials (using the late positive potential [lpp]),facial electromyography and skin-conductance response. results: our sample comprised 35 patients with ssd and 35 nonpsychotic controls. compared with controls,the patients with ssd showed blunted lpp response to pleasant stimuli (p = 0.003). across measures,cannabis-using controls showed greater response to pleasant stimuli than to cannabis stimuli whereas cannabis-using patients showed little bias toward pleasant stimuli. reduced lpp response to pleasant stimuli was predictive of more frequent subsequent cannabis use (β = -0.24,p = 0.034). limitations: it is not clear if the deficit associated with cannabis use is specific to rewarding stimuli or nonspecific to any kind of emotionally salient stimuli. conclusion: the lpp captures a rewardprocessing deficit in patients with ssd and shows potential as a biomarker for identifying patients at risk of heavy cannabis use. © 2014 canadian medical association.