L-tryptophan administered to chronic sleep-onset insomniacs: late-appearing reduction of sleep latency

The effects of 3 g l-tryptophan on sleep, performance, arousal threshold, and brain electrical activity during sleep were assessed in 20 male, chronic sleep-onset insomniacs (mean age 20.3±2.4 years). Following a sleep laboratory screening night, all subjects received placebo for 3 consecutive nights (single-blind), ten subjects received l-tryptophan, and ten received placebo for 6 nights (double-blind). All subjects received placebo on 2 withdrawal nights (single-blind). There was no effect of l-tryptophan on sleep latency during the first 3 nights of administration. On nights 4–6 of administration, sleep latency was significantly reduced. Unlike benzodiazepine hypnotics, l-tryptophan did not alter sleep stages, impair performance, elevate arousal threshold, or alter brain electrical activity during sleep.