Controlled comparison of electrophysiological sleep in families of probands with unipolar depression

This study presents polysomnographic data and psychiatric history for parents and siblings of probands with unipolar depression and short REM latency, probands with unipolar depression and normal REM latency, and normal comparison probands.

Parents and adult siblings (N = 252) of probands (N = 64) were evaluated for lifetime history of psychiatric disorders and were studied in the sleep laboratory for 3 nights.

REM latency predicted lifetime history of major depression. Short REM latency was also associated with slow wave sleep deficits. Rate of short REM latency in relatives of depressed probands with short REM latency quadrupled the rate in relatives of both depressed probands with normal REM latency and normal probands. Lifetime risk of depression was almost twice as high in relatives of depressed probands with short REM latency as in relatives of depressed probands with normal REM latency.

Short REM latency and slow wave sleep deficits are familial. Short REM latency is associated with increased risk of major depression beyond the familial risk associated with a depressed proband. Polysomnographic abnormalities also occurred in unaffected relatives. Although the data can be considered only suggestive, these findings indicate that polysomnographic abnormalities may precede the clinical expression of depression and may be useful in identifying those at highest risk for the illness.