Working memory and depressive symptoms in patients with schizophrenia and substance use disorders.

Background: Substance abuse is highly prevalent in schizophrenia and it has been associated with negative consequences on the course of the pathology. Regarding cognition, the prevailing literature has produced mixed results. Some groups have reported greater cognitive impairments in dual diagnosis schizophrenia, while other groups have described the reverse.
Objective: The current cross-sectional study sought to investigate the potential differences in psychiatric symptoms and cognition between schizophrenia patients with and without substance use disorders.
Methods: Fifty-three schizophrenia patients were divided into two groups: with (n=30) and without (n=23) a substance use disorder (DSM-IV criteria). Psychiatric symptoms were measured with the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS). Psychomotor speed and spatial working memory were measured using Cambridge Neuropsychological Tests Automated Battery (CANTAB).
Results: Patients in the dual diagnosis group displayed more severe depressive symptoms and poorer strategy during the working memory task.
Conclusions: These results are in keeping with the prevailing literature describing negative consequences of substance abuse in schizophrenia. Substance abuse may exacerbate depressive symptoms and interfere with metacognition in schizophrenia.