Abstract

The present study investigated the influence that trait hostility and serotonin may have on individuals' mood and cardiovascular responses to stress. Sixty high and low hostile males and females participated in an either an acute tryptophan depletion, a procedure that lowers brain serotonin levels, or a sham tryptophan depletion, that leaves serotonin levels unchanged, and the four resulting groups (Low Hostile-Non-Depleted, High Hostile-Non-Depleted, Low Hostile-Depleted, High Hostile-Depleted) were subsequently exposed to an interpersonal conflict. High and low hostile participants in the tryptophan depleted group reported increases in hostility-related affect following the 5.5 hour waiting phase, a period of time necessary for the full effects of the tryptophan manipulation to take effect. This finding partially supports previous research reports. There were no mood differences as a function of hostility status during this waiting period. Overall participants, regardless of grouping, exhibited a cardiovascular change pattern that is generally associated with a more relaxed state, a result that is incongruent with the increased negative affect in the tryptophan depleted groups. High hostile individuals showed a slightly less relaxed pattern during this period without any tryptophan-related differences. All participants exhibited heightened cardiovascular responses to the interpersonal conflict, as well as reduced positive affect and increased negative affect, including hostility/anger-related mood changes. Contrary to expectations, there were no differential effects of trait hostility status nor tryptophan condition. Possible reasons for these findings are explored.