Comorbid Psychopathology of Insomnia: A Validity Study of the Insomnia Severity Index Among Older Adults

The Insomnia Severity Index (ISI) is a brief screening tool that assesses the presence and severity of insomnia symptoms. Although widely validated, its psychometric properties remain understudied in older adults, a population at increased risk for insomnia due to age-related changes in sleep architecture and quality. This study assessed the concurrent and factorial validity of the ISI among community-dwelling older adults ( N = 250) who completed the ISI and measures of comorbid symptoms: Brief Geriatric Suicide Ideation Scale, Michigan Alcohol Screening Test-Geriatric Version, Geriatric Depression Scale-15, and Geriatric Anxiety Scale. Bivariate correlations supported concurrent validity, with insomnia positively associated with anxiety, depression, suicidal ideation, and alcohol misuse. Anxiety was the strongest correlate and the only unique predictor of ISI scores in multivariate analyses. Exploratory factor analysis revealed a one-factor solution. Findings support the concurrent validity and factor structure of the ISI and highlight comorbidity with other mental health symptoms among older adults.