Chronic depressions. Part 2. Sleep EEG differentiation of primary dysthymic disorders from anxious depressions.

In this clinical, psychometric and polysomnographic study, primary dysthymics (N = 20) were compared with anxious depressives (N = 22), and non-psychiatric controls (N = 11). Beck and MMPI depression scores were similar in the two affective groups. Prominent insomnia occurred in 82% of the anxious group; hypersomnia was more characteristic of the dysthymic group. On night 1, the anxious group had the poorest sleep efficiency (P less than 0.001), while dysthymics had the highest REM% (P less than 0.05) and shortest REM latency (P less than 0.01). On night 2, differences tended to be minimized, although the number of awakenings was still high (P less than 0.05) in the anxious group, and REM% was highest (P less than 0.01) and REM latency shortest (P less than 0.01) in the dysthymics. These findings suggest that patients with primary anxiety disorders experience greater sleep continuity difficulties on the adaptation night. Despite significant clinical overlap in depressive symptomatology between the two groups, REM% and REM latency appear as sturdy psychophysiological markers in differentiating primary dysthymics and anxious depressives on both nights. These data suggest that distinct anxious depressive and subaffective dysthymic subtypes can be distinguished within the universe of the atypical depressions.