The Work and Social Adjustment Scale as a Measure of Dysfunction in Chronic Insomnia: Reliability and Validity

BACKGROUND: Dysfunction is an integral part of chronic insomnia. Despite this, very little effort has yet been made to design and psychometrically validate an insomnia-specific measure of dysfunction. AIMS: The purpose was to examine the psychometric properties of the Work and Social Adjustment Scale (WSAS) as a measure of dysfunction in chronic insomnia. METHOD: Seventy-three patients with chronic insomnia from three subsamples participated. All the patients completed the WSAS, the Insomnia Severity Index (ISI), and sleep diaries over one week. RESULTS: An exploratory factor analysis suggested a one-factor solution for the WSAS, determining dysfunction, accounting for 73.7% of the variance. The internal consistency of the WSAS was α = .91. The test-retest reliability for the WSAS items was high at .90-.99 and for the entire scale .99. A cut-off at 17 points was established, discriminating those with subclinical versus moderate or severe clinical insomnia (88% sensitivity and 78% specificity). Evidence of convergent and criterion validity was documented via (1) a significant, positive association between the WSAS and ISI and (2) a higher WSAS score among those with severe clinical insomnia, relative to those with moderate clinical and subthreshold insomnia, as well as a higher WSAS score among those with moderate clinical insomnia relative to those with subthreshold insomnia. The WSAS was also shown to be a treatment-sensitive measure for insomnia patients. CONCLUSIONS: The WSAS appears as a reliable and valid measure of dysfunction in chronic insomnia. Additional advantages are its shortness, easiness, and treatment-sensitivity.