Processing of social emotion in patients with schizophrenia and substance use disorder: an fMRI study

The lifetime prevalence of substance use disorders among schizophrenia patients is close to 50%. The negative consequences of substance abuse in schizophrenia are well documented, but the aetiology of this comorbid condition remains unknown. Mounting evidence suggests that dual-diagnosis patients have fewer negative symptoms and better social skills, compared to non-abusing patients. We hypothesized that schizophrenia patients with substance use disorder (SCZ-SUD) would display increased cerebral activations in response to socioemotional stimuli, relative to patients with no SUD (SCZ). Schizophrenia patients (DSM-IV criteria) were divided into two groups: patients with (n=12) and without (n=11) substance use (alcohol and/or cannabis). Using functional magnetic resonance imaging (fMRI), patients were scanned during passive viewing of an emotional film excerpt with social content. Loci of activation were identified in the right mPFC (BA 10) and the right supramarginal gyrus (BA 40) in SCZ-SUD patients, and in the left pons in SCZ patients. Relative to SCZ patients, increased loci of activation were found in the right superior parietal cortex (BA 7) and the left medial prefrontal cortex (BA 10) in SCZ-SUD patients, who reported higher subjective emotional experience on a self-report scale. To our knowledge, this is the first fMRI study to assess social emotions in dual-diagnosis schizophrenia. Our results suggest that socioemotional processing may be less impaired in dual diagnosis, which recruited brain regions seemingly involved in "social cognition." Further studies on the topic are warranted.