Relationship between serotonin and the temperament and character inventory.

The unified biosocial theory of personality, proposed by Cloninger, conceptualises personality as a combination of heritable, neurobiologically based traits (temperament dimensions), and traits reflecting sociocultural learning (character dimensions). The temperament dimensions are thought to be related to activity in specific central neurotransmitter systems. The relationship of the dimensions of the Temperament and Character Inventory, particularly harm avoidance (HA), and platelet 5-HT2 receptor sensitivity was investigated in a sample of undergraduate student volunteers (N = 49). Serotonin-receptor binding results in Ca2+ release from intracellular stores. The concentration of serotonin required to produce half maximal Ca2+ response (EC50) is indicative of 5-HT2 receptor sensitivity such that the lower the EC50 serotonin concentration, the greater the 5-HT2 receptor sensitivity. A significant inverse correlation was found between HA and EC50 (r = -0.644, P < 0.001). Self-directedness was also significantly correlated with EC50 (r = 0.391, P = 0.005). Novelty seeking, a personality trait similar to sensation seeking, was not significantly correlated with serotonin.