Psychobiological differences between the aggression and psychoticism dimension.

Since blunted prolactin (PRL) and partly blunted cortisol responses have been reported for subjects with aggressive impulsive disorders as well as with psychopathy, it seemed worthwhile to try to separate the two types of aggression by their biological response. Since, furthermore, cortisol responses are more readily elicited by 5-HT1a challenges and prolactin responses by d-Fenfluramine or uptake inhibitors, these two types of drugs were used to answer the question if these hormone responses are suitable to differentiate between the two types of aggression. Two studies were conducted, one using 15 mg of d-Fenfluramine (d-Fen) in a double-blind placebo-controlled cross-over design in 40 males, the other using 10 mg of Ipsapirone (Ips) and placebo comparing 20 healthy males in each group. In each study subjects were divided according to above and below median aggression and psychoticism scores measured by questionnaire scales and combined into four groups defined by high and low aggression (Ag+/-) and psychoticism (P+/-) scores respectively. Analyses of covariance based an the two personality factors and the drug revealed for d-Fen cortisol nonresponse in P+ as opposed to P- and a blunted PRL response in Ag+ as opposed to Ag-. With Ips the cortisol response was positively related to Ag and not to P, while P+ showed a blunted PRL response not observed in Ag+. Joyfulness and well-being were also differentially affected by d-Fen in high and low P scorers, but not correlated to respective hormone responses. Different hypothalamic mechanism for eliciting the two hormone responses and differences in pre- and postsynaptic receptor sensitivities in the two personality dimensions are inferred from these findings.