%0 Journal Article
%T The serotonin transporter gene
%A C Rob Markus
%A Jens H van Dalfsen
%J Journal of Psychopharmacology
%@ 1461-7285
%D 2019
%R 10.1177/0269881119855978
%X The low-expressive short (S) allele of a functional polymorphism (5-HTTLPR) within the serotonin (5-hydroxytriptamine; 5-HT) transporter gene (SLC6A4) has been associated with a reduced functioning of the brain 5-HT system relative to the long (L) allele. As a consequence, the S-allele is found to predispose individuals to a higher risk of sleep quality reduction and clinical insomnia. The present study investigated whether subchronic pre-sleep tryptophan administration could compensate for this predisposition by improving sleep in 5-HTTLPR S-allele carriers. In a double-blind placebo-controlled crossover design a sample of homozygous 5-HTTLPR S-allele (n = 47) and L-allele (n = 51) carriers were assessed for subjective (sleep diary) and objective (actigraphy) sleep during a treatment protocol consisting of 1 week of placebo (1000£¿mg/day) and 1 week of tryptophan administration (1000£¿mg/day). The results support the sleep-promoting effects of tryptophan. Tryptophan improved objective sleep efficiency and objective wake after sleep onset irrespective of allelic variation. There was a marginally significant improvement of subjective sleep quality in the 5-HTTLPR S-allele group but not in the L-allele group following tryptophan relative to placebo intake. In contrast, a significantly poorer sleep quality in the S-allele as opposed to the L-allele group in the placebo condition was not observed in the tryptophan condition. Tryptophan augmentation promises to be a valuable treatment strategy for sleep impairments related to genetic deficiencies in 5-HT functioning
%K Sleep
%K insomnia
%K 5-HTTLPR
%K serotonin
%K tryptophan
%U https://journals.sagepub.com/doi/full/10.1177/0269881119855978