Genetically informed studies of the personality characteristics typical of individuals with psychopathy have found moderate genetic (as well as non-genetic) influences. On the PPI, fearless dominance and impulsive antisociality were similarly influenced by genetic factors and uncorrelated with each other. Genetic factors may generally influence the development of psychopathy while environmental factors affect the specific expression of the traits that predominate. A study on a large group of children found more than 60% heritability for "callous-unemotional traits" and that conduct problems among children with these traits had a higher heritability than among children without these traits.
A study by Farrington of a sample of London males followed between age 8 and 48 included studying which factors scored 10 or more on the PCL:SV at age 48. The strongest factors included having a convicted parent, being physically neglected, low involvement of the father with the boy, low family income, and coming from a disrupted family. Other significant factors included poor supervision, harsh discipline, large family size, delinquent sibling, young mother, depressed mother, low social class, and poor housing. There has also been association between psychopathy and detrimental treatment by peers. However, it is difficult to determine the extent of an environmental influence on the development of psychopathy because of evidence of its strong heritability
Researchers have linked head injuries with psychopathy and violence. Since the 1980s, scientists have associated traumatic brain injury, such as damage to the prefrontal cortex, including the orbitofrontal cortex, with psychopathic behavior and a deficient ability to make morally and socially acceptable decisions, a condition that has been termed "acquired sociopathy", or "pseudopsychopathy". Individuals with damage to the area of the prefrontal cortex known as the ventromedial prefrontal cortex show remarkable similarities to diagnosed psychopathic individuals, displaying reduced autonomic response to emotional stimuli, deficits in aversive conditioning, similar preferences in moral and economic decision making, and diminished empathy and social emotions like guilt or shame. These emotional and moral impairments may be especially severe when the brain injury occurs at a young age. Children with early damage in the prefrontal cortex may never fully develop social or moral reasoning and become "psychopathic individuals ... characterized by high levels of aggression and antisocial behavior performed without guilt or empathy for their victims". Additionally, damage to the amygdala may impair the ability of the prefrontal cortex to interpret feedback from the limbic system, which could result in uninhibited signals that manifest in violent and aggressive behavior