The effects of acute plasma tryptophan manipulation on hostile mood: The influence of trait hostility

The effects of acute plasma tryptophan manipulation on changes in hostile, anxious, and depressive mood were studied in 48 males. Subjects consumed tryptophan-free or nutritionally balanced amino acid mixtures as a means of manipulating brain serotonin levels. Mood (hostility, anxiety, depression) was assessed pre-and 5 hr post-ingestion using the Multiple Affect Adjective Checklist. Overall, the tryptophan manipulation resulted in significant changes in hostile mood. Analyses also revealed a stronger association between changes in plasma tryptophan and changes in hostility in subjects with high levels of pre-existing hostile traits compared with low levels of hostile traits, and in subjects with high vs. low antisocial traits. There was no significant association between changes in plasma tryptophan and changes in depression. The results suggest that persons with high levels of trait hostility may be more susceptible to the effects of acute manipulation of plasma tryptophan on hostile mood. (C) 1998 Wiley-Liss, Inc.