Mokken scaling analysis of the Hospital Anxiety and Depression Scale in individuals with cardiovascular disease.

OBJECTIVE The Hospital Anxiety and Depression Scale (HADS) is a prolifically used scale of anxiety and depression. The original bidimensional anxiety-depression latent structure of the HADS has come under significant scrutiny, with previous studies revealing one-, two-, three- and four-dimensional structures. The current study examines the latent structure of the HADS using a non-parametric item response theory method. METHOD Using data conglomerated from four independent studies of cardiovascular disease employing the HADS (n=893), Mokken scaling procedure was conducted to assess the latent structure of the HADS. RESULTS A single scale consisting of 12 of 14 HADS items was revealed, indicating a unidimensional latent HADS structure. DISCUSSION The HADS was initially intended to measure mutually exclusive levels of anxiety and depression; however, the current study indicates that a single dimension of general psychological distress is captured.