title: Do reward-processing deficits in schizophrenia-spectrum disorders promote cannabis use? An investigation of physiological response to natural rewards and drug cues.
abstract: 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).
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  The LPP captures a reward-processing deficit in patients with SSD and shows potential as a biomarker for identifying patients at risk of heavy cannabis use.
authors.affiliation: Department of Psychiatry, McGill University, Montreal, Que., Canada and the Department of Psychiatry, Columbia University, New York, NY, USA.
authors.forename: Clifford M
authors.initials: CM
authors.lastname: Cassidy
authors.affiliation: Department of Psychiatry, McGill University, Montreal, Que., Canada.
authors.forename: Mathieu B
authors.initials: MB
authors.lastname: Brodeur
authors.affiliation: Department of Psychiatry, McGill University, Montreal, Que., Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Lepage
authors.affiliation: Department of Psychiatry, McGill University, Montreal, Que., Canada.
authors.forename: Ashok
authors.initials: A
authors.lastname: Malla
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D002188:Cannabis; D003463:Cues; D004569:Electroencephalography; D004576:Electromyography; D005074:Evoked Potentials, Visual; D005152:Facial Muscles / Q000503:physiopathology; D005712:Galvanic Skin Response; D020010:Heterosexuality; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D011379:Prognosis; D011618:Psychotic Disorders / Q000150:complications / Q000503:physiopathology* / Q000523:psychology*; D012201:Reward; D012565:Schizophrenic Psychology; D014029:Tobacco Use Disorder / Q000150:complications / Q000503:physiopathology / Q000523:psychology; D014796:Visual Perception / Q000502:physiology*