REM latency distribution in major depression: Clinical characteristics associated with sleep onset REM periods

In a sample of 92 inpatients with major depression, REM latency showed a unimodal, rather than bimodal, distribution, with peak frequency between 50-59 min (on each side of 4 consecutive nights). A total of 20 patients (21.6%) exhibited a sleep onset REM period (SOREMP-10) i.e., REM latency ≤ 10 min, during at least 1 of the 4 nights; an additional 11 patients (12%) showed REM latencies of 11-20 min on at least one night. SOREMP-10 positive patients were older both at the time of study (p < 0.01) and at the age of onset of depressive illness (p < .01) than the rest of the sample. They also showed greater sleep continuity disturbances, while patients with at least one SOREMP-20, i.e., REM latency ≤ 20 min, exhibited higher REM percentage (p ≤ 0.05) and a higher first-period density (p < 0.05) than the remaining patients. No other clinical or polysomnographic correlates of SOREMP positivity were noted with regard to gender, RDC subtypes, severity of illness, or clinical response to tricyclic antidepressants. The unimodal distribution of REM latency, as well as the absence of a relationship between SOREMP positivity and severity of depression or therapeutic outcome, may result from the low representation of psychotic depressives in this sample (n = 6), who might constitute a qualitatively different subgroup.