The social dysfunction index (SDI) for patients with schizophrenia and related disorders.

The social dysfunction index (SDI) is a new measure designed to assess social dysfunction in schizophrenia and other severe mental illnesses. It is intended to serve clinical and research purposes. Raters can be readily trained and there is low respondent burden with its use. Good psychometric properties were identified in three studies (sample sizes 33, 67 and 113). The SDI assesses a wide and comprehensive range of social functioning. It includes objective assessment of dysfunction and subjective client assessment of satisfaction with functioning. It produces a summary score, a satisfaction score and a score for each of the nine components of social functioning assessed. Internal consistency is good (alpha = 0.80). Inter-rater reliability is high (r = 0.96). Use of the component scores was confirmed by factor analysis. There is modest correlation with other measures of social functioning. Evidence of construct validity is demonstrated by findings of differences in social dysfunction between subjects who lived independently vs. those who lived in boarding homes; differences between subjects who were unemployed vs. subjects who were employed; and independence of social functioning from both age and education.