Serotonergic functioning correlates with positive and negative affect in psychiatrically healthy males

A large animal literature implicates serotonin (5-HT) in the modulation of positive and negative affective behavior. In contrast, data from human studies almost exclusively emphasize 5-HT modulation of negative emotional processing. However, no previous studies have directly assessed the relation between 5-HT functioning and positive (PA) and negative (NA) affect. The present investigation tested whether individual differences in 5-HT functioning correlate with PA and NA ratings in a group of healthy subjects. Thirty-one psychiatrically healthy males completed separate assessments of affect and 5-HT functioning. Affect was examined with the Positive and Negative Affect Schedule rated three times a day for two work-weeks. 5-HT functioning was indexed by the maximum prolactin response to d,l-fenfluramine. The prolactin response to d,l-fenfluramine demonstrated a significant inverse correlation with mean ratings of both PA (r=−0.49; p<0.005) and NA (r=−0.42; p<0.05). These data provide evidence that 5-HT exerts an inhibitory influence over both PA and NA in humans, such that individual differences in 5-HT functioning inversely correlate with ratings of affect.