A psychometric assessment of the GAIN Individual Severity Scale (GAIN-GISS) and Short Screeners (GAIN-SS) among adolescents in outpatient treatment programs

The Global Appraisal of Individual Needs (GAIN) - General Individual Severity Scale (GAIN-GISS), and GAIN-Short Screener (GAIN-SS) are widely used diagnostic measures of internalizing disorders, externalizing disorders, substance abuse, and criminal and violent behavior. Although prevalent in clinical and research settings, there is only limited psychometric evidence of the dimensional structure of these scales. Our investigation used intake data from 6,909 adolescents presenting to outpatient substance abuse treatment facilities in the United States. Our analytic approach used exploratory and item factor analyses to evaluate the underlying factor structure. Multi- and unidimensional item response theory models were employed to evaluate the utility of the scales at providing precise score estimates at various locations of severity. Most scales were confirmed as unidimensional; scales with evidence of multidimensionality, identified as having a weak general dimension and strong specific dimensions using a bifactor IRT model, include the Crime and Violence Scale and the GAIN-SS.