Background: A slow-wave sleep (SWS) deficit and a shortened rapid eye movement (REM) sleep latency are commonly described in schizophrenia and depression. In addition, a close association between ventricular system measurements and SWS are reported in both disorders; however, a comparative, combined polysomnographic and computed tomographic investigation is lacking.
Methods: In the present post hoc study we analyzed the electroencephalographic sleep pattern and the ventricular brain ratio (VBR) of 14 drug-naive schizophrenic patients and of 14 depressed patients who were drug-free for a sufficient time period.
Results: Whereas the depressives showed the often described SWS and REM sleep changes, these measurements were quite normal in the schizophrenics. The VBR values were similar in both patient groups and exceeded in 71% of the schizophrenics and in 50% of the depressives the cutoff point of a "normal" VBR value. A close association between SWS and VBR was found in the depressives but not in the schizophrenics.
Conclusions: The results of the present study of drug-naive schizophrenic patients and of depressed patients indicate only a minor overlap between the pathophysiological changes observed in both disorders. Therefore, the present investigation adds evidence for the assumption that schizophrenia and depression are etiopathogenetically distinct entities, rather than representing points on a continuum of liability.