FIRST-NIGHT EFFECT IN NORMAL SUBJECTS AND PSYCHIATRIC-INPATIENTS

The goal of the present study was to evaluate the first-night effect i n psychiatric inpatients using large subject samples (n > 30) in order to obtain a good statistical evaluation. Thirty-two normal subjects a nd 94 psychiatric inpatients (38 depressives and 56 insomniacs) were s tudied for three consecutive nights in the hospital sleep laboratory. Our results showed clearly that there was a first-night effect in norm al subjects, similar to that reported in previously published data, ch aracterized by a longer rapid eye movement (REM) sleep latency (p < 0. 05), increased wakefulness (p < 0.01) and total sleep time (p < 0.02) and a decreased sleep efficiency (p < 0.01). REM sleep latency and sta ge REM in the first third of the night were still altered in the secon d night. Both clinical groups had a less marked first-night effect tha n normal subjects, showing alterations only observed in REM sleep (p < 0.01) (decreased REM sleep, longer REM sleep latency, increased REM s leep gravity center). However, the first-night effect was more pronoun ced in insomniacs than in depressed patients. No statistical differenc es between the second and third nights' recordings were found in sleep parameters. It is suggested that first-night data should not be simpl y discarded but could be used in subsequent analyses.