Development and validation of short versions of the internal mental distress and behavior complexity scales in the Global Appraisal of Individual Needs (GAIN).

Co-occurring mental distress and behavior problems are the norm in substance abuse treatment but are often poorly assessed due to resource constraints. This paper describes the development and validation of scales measuring internalizing mental distress and externalizing behavior problems that are shorter versions of comorbidity scales found in the full Global Appraisal of Individual Needs (GAIN). GAIN data from two treatment outcome studies, one involving adolescents and the other on adults, were used in the creation and testing of the scales. Subsets of items from the full GAIN scales were selected for the short scales through the application of standard psychometric principles. The short comorbidity scales still have moderate to high reliability and are highly correlated with the full scales. Parallel tests of construct validity show no substantial loss when moving from the longer to shorter versions. The short scales maintain good sensitivity and specificity for predicting diagnostic impressions.