||Objective. Irritable and nonirritable depressed patients differ on demographic and clinical characteristics. We investigated whether
this extends to psychological and physiological measures. Method. We compared irritable and nonirritable unipolar depressed
patients on symptomatology, personality, and (psycho)physiological measures (cortisol, cholesterol, and heart rate variability).
Symptomatology was reassessed after one year, and we also compared depressed patients who were irritable or non-irritable at
both time points (Irr++ versus Irr−−). Results. Almost half (46%; N = 420) of the sample was classified as irritable. These
patients scored higher on depression severity, anxiety, hypomanic symptoms, and psychological variables. No differences were
observed on physiological markers after correction for depression severity. The same pattern was found when comparing Irr++
and Irr-- groups. Conclusion. Irritable and non-irritable depressed patients differ on clinical and psychological variables, but not
on the currently investigated physiological markers. The clinical relevance of the distinction and the significance of the hypomanic
symptoms remain to be demonstrated.