Nine depressed inpatients slept from ten to 32 nights in the lab. Night-by-night fluctuations in their EEG sleep recordings were correlated with daily changes in Beck depression scores. A "percentage of phasic REM" measurement was obtained nightly by computing the percentage of 30-second epochs during REM containing at least one eye movement. Nightly fluctuations in percent phasic REM were inversely related to day-by-day changes in depression. This relationship was found whether a patient was treated with ECT or antidepressants. The results suggest that depression might be related to the malfunctioning of a pontine sero serotenergic gating mechanism for the control of PGO spiking during the REM.
Hauri P, Hawkins DR. Phasic REM, Depression, and the Relationship Between Sleeping and Waking. Arch Gen Psychiatry. 1971;25(1):56-63. doi:10.1001/archpsyc.1971.01750130058006