Effects of L-tryptophan on daytime arousal

A double-blind placebo-controlled study was carried out on 20 subjects to examine the early morning sedative effects of 2 g of L-tryptophan. Using brain mapping technique, 16-channel EEG recordings were topographically displayed. A distinct increase in theta amplitude, predominantly in the central region, together with an alpha reduction was observed after L-tryptophan administration, signs characterizing the EEG of drowsiness. Subjective self-rated sleepiness increased after the ingestion of L-tryptophan. Psychomotor performance, assessed by means of various psychometric tests, was not affected by this low dose of L-tryptophan.