Several lines of evidence suggest that there may be abnormal brain serotonin metabolism in habitually biolent and impulsive offenders. These personality disorders are usually connected with early onset, male limited type 2 alcoholism in which one central feature is the abnormal tendency to behave aggressively and impulsively under the influence of alcohol repeatedly. Low CSF 5-HIAA has been found to correlate with familial alcoholism tendencies; paternal alcoholism. Both this and with it the tendency to abnormal oral glucose tolerance test (tendency to low blood glucose nadir) predict the new violent and impulsive crimes under the influence of alcohol. Also peripheral measures such as platelet MAO, abnormal tryptophan/LNAA ratio in plasma, whole blood serotonin, blood platelet uptake of serotonin, platelet 3H-IMI dinging (Bmax), abnormal prolactin and Cortisol secretion in fenfluramine challenge, and possibly daily urinary free Cortisol secretion correlate with impulsive aggressive behavior.

Because of the graded nature of adaptational processes, a dimensional diagnostic approach is more adequate than the categorical classification. The broad concept of the serotonin-aggression relationship, irrespective of the diagnostic category, is increasingly questionable and seems to be present in young, white male adults with antisocial personality disorders only. In this group, dopaminergic and neurosteroid-linked mechanisms are important as well.