A 32-year-old woman with severe depressive disorder undergoes polysomnography. Compared with age-matched controls, which finding would be MOST characteristic of her study?

• A Prolonged REM latency with reduced total REM time
• B Shortened REM latency with increased REM density in the first sleep period ✓
• C Increased proportion of stage N3 slow-wave sleep
• D Absence of sleep spindles throughout the night

Explanation

Normal REM latency is about 70 to 90 minutes. In endogenous depression it is characteristically shortened, with early REM intrusion and increased REM density, findings also seen in narcolepsy. Total REM time is increased rather than reduced, and stage N3 slow-wave sleep is decreased, not increased, in depression. Spindle generation by the thalamic reticular nucleus remains intact.

Reference: Kaplan and Sadock's Synopsis of Psychiatry, 12th ed.

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