Objectives: Depression and vital exhaustion are associated with poor cardiovascular prognosis, but there is substantial overlap between these constructs. Factor analytic studies have been inconclusive, and may not be the optimal analytic strategy to assess dimensionality. We assessed whether exhaustion and depression formed a single, hierarchical dimension using a form of nonparametric item response theory.
Methods: Patients with acute coronary syndrome (n = 430) completed questionnaires assessing depression and vital exhaustion. Mokken scaling was used to assess dimensionality.
Results: Mokken scaling formed a strong unidimensional scale, ordered in a hierarchy reflecting prevalence: fatigue (common), depression (less common) and hopelessness (rare).
Conclusions: Depressive symptoms form a clear hierarchy in cardiac patients, from fatigue to hopelessness. Vital exhaustion may be considered a less severe form of depression. Use of hierarchical scales may allow clinicians to better determine clinical significance and target interventions.