Is the Addiction Severity Index a reliable and valid assessment instrument among clients with severe and persistent mental illness and substance abuse disorders ?

This study examined aspects of reliability, validity and utility of Addiction Severity Index (ASI) data as administered to clients with severe and persistent mental illness (SMI) and concurrent substance abuse disorders enrolled in a publicly-funded community mental health center. A total of 62 clients with SMI volunteered to participate in an interobserver and test-retest reliability study of the ASI. Spearman-Brown and Pearson correlation coefficients were calculated to examine the extent of agreement among client responses. Overall 16% of the composite scores could not be calculated due to missing data and 31% of the clients misunderstood or confused items in at least one of the seven ASI domains. As a whole, the interobserver reliability of the ASI composite scores for those subjects where sufficient data were available was satisfactory. However, there was more variance in the stability of client responses, with four composite scores producing test-retest reliability coefficients below .65. Evidence from this study suggests that the ASI has a number of limitations in assessing the problems of clients with severe and persistent mental illness, and it is likely that other similar instruments based on the self-reports of persons with severe and persistent mental illness would also encounter these limitations.