Familial liability to schizophrenia: a sibling study of negative symptoms.

Negative symptoms are important features in schizophrenia, so in milder form they might also serve as indicators of "unexpressed" liability to schizophrenia among patients' adult relatives without schizophrenia. To address this question, we assessed negative symptoms in 39 stable schizophrenia or schizoaffective outpatients, 39 of their siblings, 38 well control probands, and 38 of their siblings. Negative symptom measures included standard behavior ratings of the core negative symptoms of affective flattening and alogia, as well as a self-report measure of social anhedonia. As expected, even stable outpatients with schizophrenia exhibited significantly more negative symptoms than control probands and control siblings. However, negative behavioral symptoms of affective flattening, alogia, and anhedonia did not significantly differentiate the siblings of the schizophrenia patients from the control probands or their siblings, although there were some trends for anhedonia. The findings suggest that core negative symptoms of observed affective flattening and poverty of speech are not likely to be useful as strong indicators of "unexpressed" liability to schizophrenia.