The effects of tryptophan depletion and loading on laboratory aggression in men: Time course and a food-restricted control

James M. Bjork, Donald M. Dougherty, F. Gerard Moeller, Don R. Cherek, Alan C. Swann

Research output: Contribution to journalArticle

107 Scopus citations


Some studies have shown that sharp reduction of L-tryptophan (Trp) concentration in plasma results in increases in laboratory-measured aggression. Conversely, raising plasma Trp has blunted aggression. These effects are presumably due to impaired or enhanced serotonin synthesis and neurotransmission in the brain. In this study, the laboratory-measured aggressive behavior of eight men under both Trp depletion (T-) and Trp loading (T+) conditions was compared to their aggressive behavior under food- restricted control conditions (overnight fast without an amino acid beverage). Subjects were provoked by periodic subtraction of money which was attributed to a fictitious other participant, and aggression was defined as the number of retaliatory responses the subject made ostensibly to reduce the earnings of the (fictitious) other participant. Following ingestion of the T- beverage, aggressive responding was significantly elevated relative to the food-restricted control condition, and this increased aggressive behavior became more pronounced across behavioral testing sessions on a time-course which paralleled previously documented decreases in plasma Trp concentrations. In contrast, no changes were observed in aggressive responding tinder T+ conditions relative to food-restricted conditions. These within-subject behavioral changes under depleted plasma Trp conditions support earlier indications of a role of serotonin in regulating aggression.

Original languageEnglish (US)
Pages (from-to)24-30
Number of pages7
Issue number1
StatePublished - May 5 1999



  • Aggression
  • Diet
  • Human
  • Serotonin
  • Tryptophan

ASJC Scopus subject areas

  • Pharmacology

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