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 of 4 consecutive nights). A total of 20 patients (21.6%) exhibited a sleep onset REM period (SOREMP-10) i.e., REM latency less than or equal to 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 less than 0.01) and at the age of onset of depressive illness (p less than .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 less than or equal to 20 min, exhibited higher REM percentage (p less than or equal to 0.05) and a higher first-period density (p less than 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.