Background Neuroendocrine dysregulation and disturbed sleep, frequently seen in major depression, may interfere with circadian blood pressure regulation. Design and methods Using a portable device, 24 h blood pressure profiles were registered in 69 depressed inpatients and 26 hospitalized, non-depressed comparison subjects. The use of anti hypertensive medication was considered to be indicative of known arterial hypertension. Mean systolic and diastolic blood pressure levels were compared between the group of depressed patients not taking antihypertensive medication and the healthy comparison subjects, both for the entire 24 h of measurement, and for the daytime and night-time periods. In a subgroup of patients, circadian blood pressure follow-up data were obtained after 5 weeks of antidepressant therapy. Results Depressed patients not receiving antihypertensive medication (n = 52) had higher mean 24 h systolic blood pressure levels than non-depressed comparison subjects (1125.5 +/- 14.7 versus 119.6 +/- 13.3 mmHg, P<0.05). Subgroup analysis revealed that this difference could be almost exclusively attributed to patients on hypnotic medication; this subgroup also had a high day/night blood pressure change ('dip'). In depressed patients using anti hypertensive agents (n = 17), circadian blood pressure levels pointed to a suboptimal control of hypertension. In the subgroup with follow-up measurements, circadian blood pressure levels had not changed after 5 weeks of antidepressant therapy. Conclusion Circadian blood pressure monitoring identified a subgroup of depressed patients characterized by higher mean systolic blood pressure levels, the use of hypnotics and a high day/night blood pressure change. (C) 2003 Lippincott Williams Wilkins.