The effect of tryptophan on the cortisol response to social stress is modulated by the 5-HTTLPR genotype.
OBJECTIVE
The S'/S' (S/S, S/Lg and Lg/Lg) variant of the serotonin (5-HT) transporter gene linked polymorphic region (5-HTTLPR) is associated with less efficient neurotransmission and may be more reactive to 5-HT manipulations. We tested the effects of l-tryptophan supplements on the cortisol response induced by a social stressor in S'/S' and L'/L' (La/La) carriers.


METHODS
In a double-blind parallel design, 25 S'/S' carriers and 21 L'/L' carriers were randomised to take l-tryptophan (2.8g/d) or placebo supplements for six days. At day 7 participants were exposed to the Trier Social Stress Test. Salivary cortisol and subjective mood states were monitored before, during and after the stress procedure.


RESULTS
S'/S' carriers who took l-tryptophan supplements had a significantly lower cortisol response to stress than S'/S' carriers who took placebo. Tryptophan had no effect on cortisol in L'/L' carriers and no effect on subjective mood states in either genotype group.


CONCLUSIONS
Tryptophan attenuates the cortisol response to acute social stress depending on 5-HTTLPR genotype. S'/S' carriers may indeed be more reactive to 5-HT manipulations.
Institute of Psychology, Leiden University, Leiden, The Netherlands; Leiden Institute for Brain and Cognition, Leiden, The Netherlands.
Hilâl
H
Cerit
Linda A W
LA
Jans
Willem
W
Van der Does
D000293:Adolescent; D000328:Adult; D000339:Affect / Q000187:drug effects; D004311:Double-Blind Method; D005260:Female; D005838:Genotype; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008297:Male; D010349:Patient Compliance; D011110:Polymorphism, Genetic / Q000235:genetics; D012463:Saliva / Q000378:metabolism; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics*; D013315:Stress, Psychological / Q000235:genetics / Q000378:metabolism*; D014364:Tryptophan / Q000494:pharmacology*
D050486:Serotonin Plasma Membrane Transport Proteins; D014364:Tryptophan; D006854:Hydrocortisone