REM sleep latency and morbidity risk of affective disorders in depressive illness

The relationship between rapid eye movements (REM) sleep latency and morbidity risks for affective illness in first-degree relatives of affectively ill probands was investigated in 122 patients suffering from primary major depressive disorder (74 unipolars, 48 bipolars) according to the Research Diagnostic Criteria. Sleep EEG scoring was done blind to the clinical diagnosis of the probands and their relatives, and the evaluation of morbidity risks for affective illness in first-degree relatives was done using Strömgren's method with age correction. A logistic regression analysis was performed to describe the proportion of affectively ill relatives as a function of variables recorded in 122 probands with primary major depression. Our analysis demonstrates an inverse relationship between REM sleep latency and the risk for depressive disorder in the families of affectively ill probands. These results suggest the possibility that common pathophysiological factors may be involved in the hereditary predisposition to affective illness and in the shortening of REM sleep latency in some depressed patients.