Selectivity in response to L-tryptophan among insomniac subjects: a preliminary report.

The hypnotic effects of l-tryptophan (1 g), secobarbital (100 mg), and flurazepam (30 mg), relative to placebo, were evaluated in a sample of 54 outpatient chronic insomniacs with a major complaint of sleep maintenance insomnia. Three mutually exclusive complaints about sleep maintenance were identified. Analysis of the data from the tryptophan condition indicated that the single factor type of sleep maintenance complaint accounted for 100% of the variance in a measure reflecting a single overall assessment of tryptophan's hypnotic effect, and 52% of variance in a second, repeated measure assessing subjects' day-to-day experience with the treatment. It is concluded that the distinctions in sleep maintenance insomnia identified are likely to be clinically meaningful. The distinct profiles of the tryptophan responders and nonresponders are described, and the utility of the distinctions in understanding the differential effects of flurazepam and secobarbital discussed. The implications of the finding for a number of sleep disorder-related issues were addressed.