Breed specific behavioural traits
such as hunting, herding and calmness / aggression are, however, evidence of a large genetic component and specific behaviours show
high heritabilities [4 - 8].
Rather fewer meet the diagnostic criteria for research, which for the oppositional defiant type of conduct disorder seen in younger children require at least four specific behaviours to be present.7 The early onset pattern — typically beginning at the age of 2 or 3 years — is associated with comorbid psychopathology
such as hyperactivity and emotional problems, language disorders, neuropsychological deficits
such as poor attention and lower IQ,
high heritability, 8 and lifelong antisocial behaviour.9 In contrast, teenage onset antisocial behaviour is not associated with other disorders or neuropsychological deficits, is more environmentally determined than inherited, and tends not to persist into adulthood.9