Background: Deficits in emotion processing may be one of the most pervasive disturbances in schizophrenia that may contribute to social isolation. In this report we focus on vocal emotion processing. This function bears upon two corner stones of social functioning, language and emotion, which have both been found to be impaired in schizophrenia.
Methods: We used meta-analysis to integrate findings of studies published between 1980 and June 2007 on perception of emotional prosody in schizophrenia. 17 studies provided sufficient information to be included. A mean weighted effect size was computed in the random effects model. Publication bias was tested using funnel plots and fail-safe number of studies. Seven studies were included in an analysis on the expression (i.e. production) of emotional prosody in schizophrenia.
Results: A significant and stable mean weighted effect size was found for the perception of emotional prosody, d=-1.24, 95% CI=-1.55 to -0.93. The effect was also found in the early stages of the illness. Expression of emotional prosody was also significantly impaired, d=-1.11, 95% CI=-1.78 to -0.43.
Conclusions: Results indicate that individuals with schizophrenia are impaired in the perception and expression of emotional prosody, with a large effect size. As a growing body of evidence shows that impaired social cognition in schizophrenia may be an important predictor of social outcome, training programs that aim at the recognition of emotional prosody should be developed.