A meta-analysis of 20 studies found significantly lower 5-HIAA levels (indicating lower serotonin levels), especially in those who are younger than 30 years of age.While it has been shown that lower levels of serotonin may be associated with ASPD, there has also been evidence that decreased serotonin function is highly correlated with impulsiveness and aggression across a number of different experimental paradigms. Impulsivity is not only linked with irregularities in 5HT metabolism, but may be the most essential psychopathological aspect linked with such dysfunction. Correspondingly, the DSM classifies "impulsivity or failure to plan ahead" and "irritability and aggressiveness" as two of seven sub-criteria in category A of the diagnostic criteria of ASPD.Some studies have found a relationship between monoamine oxidase A and antisocial behavior, including conduct disorder and symptoms of adult ASPD, in maltreated children. Neurological
Antisocial behavior may be related to head trauma. Antisocial behavior is associated with decreased grey matter in the right lentiform nucleus, left insula, and frontopolar cortex. Increased volumes have been observed in the right fusiform gyrus, inferior parietal cortex, right cingulate gyrus, and post central cortex.Intellectual and cognitive ability is often found to be impaired or reduced in the ASPD population. Contrary to stereotypes in popular culture of the "psychopathic genius", antisocial personality disorder is associated with both reduced overall intelligence and specific reductions in individual aspects of cognitive ability.
Antisocial personality disorder (ASPD or infrequently APD) is a personality disorder characterized by a long-term pattern of disregard of, or violation of, the rights of others as well as a difficulty sustaining long-term relationships. Lack of empathy is often apparent, as well as a history of rule-breaking that can sometimes include law-breaking, a tendency towards substance abuse, and impulsive and aggressive behavior. Antisocial behaviors often have their onset before the age of 8, and in nearly 80% of ASPD cases, the subject will develop their first symptoms by age 11. The prevalence of ASPD peaks in people age 24 to 44 years old, and often decreases in people age 45 to 64 years. In the United States, the rate of antisocial personality disorder in the general population is estimated between 0.5 and 3.5 percent. In a study, a random sampling of 320 newly incarcerated offenders found ASPD was present in over 35 percent of those surveyed.Antisocial personality disorder is defined in the Diagnostic and Statistical Manual of Mental Disorders (DSM), while the equivalent concept of dissocial personality disorder (DPD) is defined in the International Statistical Classification of Diseases and Related Health Problems (ICD); the primary theoretical distinction between the two is that antisocial personality disorder focuses on observable behaviours, while dissocial personality disorder focuses on affective deficits. Otherwise, both manuals provide similar criteria for diagnosing the disorder. Both have also stated that their diagnoses have been referred to, or include what is referred to, as psychopathy or sociopathy.