Patients with schizophrenia show deficits in many cognitive domains and social functioning, social skills, and self management skills in their daily life activities.

To evaluate the relationship between general-social cognition, mental state and social functioning, and impact on quality of life.

Twenty patients with chronic disorder of schizophrenia were evaluated and compared with 20 siblings and 20 healthy controls regarding performance in a series of tests: Cognitive Screening: Word Accentuation Test, MCCB (Matrics Consensus Cognitive Battery) Social Functioning: UPSA (University of California Performance Skills Assessment), TABS (Test of Adaptive Behaviour in Schizophrenia), SSPA (Social Skills Performance Assessment), Beck and Hamilton depression scales, Scale for Positive and Negative Syndrome of Schizophrenia, and SF-36 as indicator of quality of life.

Patients showed significant differences from controls and siblings in MCCB total score (p < 0.001), whereas siblings showed significant differences compared to controls in MCCB total score (p = 0.053). Siblings performed differently from patients (p < 0.001) and controls (p = 0.019) in social functioning measured with TABS. A series of correlations between general cognition and social functioning were demonstrated for patients and their unaffected siblings (not shown).

Results suggest that the performance of nonpsychotic siblings is located between patients and healthy controls, suggesting that social performance measures are (or associated with) intermediate phenotypes of the disease. General and social cognition have a complex relationship with social functioning and quality of life.