Differentiation between Severe major depression and schizophrenia is oftenly a problematic issue, whether due to resemblance between negative symptoms of schizophrenia and depressive symptoms or due to presence of psychotic features with psychiatrists subjective assessment of the volume of psychotic features in relation to the whole illness. Our aim is to assess the utility of polysomnography as a differentiating tool that may add diagnostic value.

Patients were recruited randomly from the outpatient service at Alexandria University Hospital, 20 patients with severe major depression with or without psychotic features and 20 patients with schizophrenia. Diagnosis done in accordance with criteria of DSM IV-TR. Only patients scoring above 4 on the Clinical Global Impression scale for severity were recruited. Polysomnography was done to all patients while at least 1 week off medication.

Depressed group showed a significantly shorter REM latency (26 ± 6.9min) and higher REM intensity (34 ± 14%) compared to schizophrenic group with REM latency (43.9 ± 16.9 min) and REM Intensity (21.4 ± 4.5). On the other hand deep sleep phases 3 and 4 constituted 12 ± 3.8% and 17.8 ± 9.2% of sleep in schizophrenic group compared to 16.4 ± 5% and 9 ± 7.9% in depressed group respectively with significant difference.

Polysomnography may be of benefit as a diagnostic differentiating tool between schizophrenia and severe Major depression.