Development and validation of the Overall Depression Severity and Impairment Scale.

The need to capture severity and impairment of depressive symptomatology is widespread. Existing depression scales are lengthy and largely focus on individual symptoms rather than resulting impairment. The Overall Depression Severity and Impairment Scale (ODSIS) is a 5-item, continuous measure designed for use across heterogeneous mood disorders and with subthreshold depressive symptoms. This study examined the psychometric properties of the ODSIS in outpatients in a clinic for emotional disorders (N = 100), undergraduate students (N = 566), and community-based adults (N = 189). Internal consistency, latent structure, item response theory, classification accuracy, convergent and discriminant validity, and differential item functioning analyses were conducted. ODSIS scores exhibited excellent internal consistency, and confirmatory factor analyses supported a unidimensional structure. Item response theory results demonstrated that the ODSIS provides more information about individuals with high levels of depression than those with low levels of depression. Responses on the ODSIS discriminated well between individuals with and without a mood disorder and depression-related severity across clinical and subclinical levels. A cut score of 8 correctly classified 82% of outpatients as with or without a mood disorder; it evidenced a favorable balance of sensitivity and specificity and of positive and negative predictive values. The ODSIS demonstrated good convergent and discriminant validity, and results indicate that items function similarly across clinical and nonclinical samples. Overall, findings suggest that the ODSIS is a valid tool for measuring depression-related severity and impairment. The brevity and ease of use of the ODSIS support its utility for screening and monitoring treatment response across a variety of settings.