Objective: This study evaluated the psychometric properties of the 15-item alcohol Short Index of Problems (SIP) instrument and those of a newly constructed 15-item drug Short Index of Problems (SIP-D) instrument in 277 newly entered substance-abuse patients.
Method: The SIP is derived from the longer, 50-item Drinker Inventory of Consequences (DrInC), which was designed to assess adverse consequences of alcohol use. The SIP-D was constructed by substituting the term "drug use" for the term "drinking" in each SIP item. A 3-month recall interval was employed.
Results: Factor analyses of each of the instruments revealed similar solutions, with only one main factor accounting for the majority of variance. Nonparametric item response theory methods produced the same finding. Internal consistency reliability estimates for the SIP and SIP-D total scores were .98 and .97, respectively. Concurrent validity was demonstrated by examining the correlations of the total scores for each of the instruments with the recent summary indexes of the newly revised Addiction Severity Index (ASI-Version 6): alcohol, drug, medical, economic, legal, family/social, and psychiatric problems.
Conclusions: This study is the first to confirm the psychometric validity of the SIP when used as an independent instrument unembedded within the DrInC. The study also supports the use of the SIP-D as a brief measure of adverse consequences of drug use. The findings strongly support the unidimensional structure of both measures.