Reduced Electrophysiological Response To Pleasant Images In Young Schizophrenia-Spectrum Patients: Association With Future Cannabis Use

Presentation First Author: 
Clifford Cassidy

Background: multiple lines of evidence point to reward system dysfunction in schizophrenia-spectrum disorders (SSD) and substance-use disorders but there has been a lack of neurobiological research to test if blunted response to naturally reinforcing stimuli promotes substance use in SSD. Method: Response to emotional images and to visual cannabis cues was assessed in young SSD patients with (n = 20) and without (n = 12) cannabis use and controls with (n = 19) and without (n = 11) cannabis use. Event-related electroencephalography (ERP, using the late positive potential, LPP) and facial electromyography measured attentional allocation and facial expressivity in response to stimuli. Frequency of cannabis use 1 month post-testing was also assessed. Results: Compared to controls, SSD patients showed decreased LPP response to pleasant images (p = .018, Bonferroni corrected) but not cannabis images (p = .65). The zygomatic and corrugator facial muscles showed blunted response to positive stimuli in cannabis-using patients and controls but the effect did not survive Bonferroni correction. Higher cannabis use 1 month post-testing was predicted by lower response to positive images compared to cannabis images as measured by ERP (beta = -.40, p = .030). Conclusion: Unlike controls, SSD patients did not show an attentional bias favouring pleasant stimuli over cannabis stimuli. This characteristic of SSD patients was predictive of higher future cannabis consumption. These results provide evidence in favour of the theory that drug abuse in schizophrenia-spectrum disorders may be driven, in part, by reward system dysfunction in these disorders.

Conference Name: 
Presentation Date: 
January, 2013
Additional Authors: 
Clifford Cassidy, Mathieu Brodeur, Martin Lepage, Ashok Malla
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