All-night electroencephalographic (EEG) sleep recording and cranial computed tomography were performed in 24 inpatients with major depression (14 unipolar, 10 bipolar). The patients showed the characteristic "depression-like" EEG sleep alterations and their ventricular brain ratio (VBR) was increased compared with the control subjects. No major differences were found between the unipolar and the bipolar groups. There was a close and positive association between the VBR values and several measures of slow wave sleep. It is hypothesized that this relationship is due to an altered function of the limbic-hypothalamic-pituitary-adrenocortical axis in depression that affects both EEG sleep and brain morphology.