title: A longitudinal twin study of the direction of effects between psychopathic personality and antisocial behaviour.
abstract: BACKGROUND
  Antisocial behaviour may partly develop as a consequence of psychopathic personality. However, neither the direction of effects nor the aetiology of the association has previously been clarified. The aim in this study was to investigate the direction of effects between psychopathic personality and antisocial behaviour, and to investigate the genetic and environmental contribution to this association.
  
  
  METHODS
  Twins (n = 2,255) in the Swedish Twin Study of Child and Adolescent Development were prospectively followed from adolescence to adulthood. We used a longitudinal cross-lagged twin model to study the associations between psychopathic personality and antisocial behaviour.
  
  
  RESULTS
  Psychopathic personality in mid-adolescence predicted antisocial behaviour in adulthood (p < .001), but not the other way around. However, bidirectional effects were found when a measure of persistent antisocial behaviour (from age 8-9 to age 16-17) was used. Psychopathic personality predicted both rule-breaking behaviour (p < .001) and aggressive behaviour (p < .01). Genetic factors were of importance in mediating the longitudinal associations between psychopathic personality and antisocial behaviour.
  
  
  CONCLUSIONS
  This study provides evidence that genetically influenced psychopathic personality is a robust predictor of adult antisocial behaviour, but also that persistent antisocial behaviour has an impact on adult psychopathic personality via genetic effects.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. mats.forsman@ki.se
authors.forename: Mats
authors.initials: M
authors.lastname: Forsman
authors.forename: Paul
authors.initials: P
authors.lastname: Lichtenstein
authors.forename: Henrik
authors.initials: H
authors.lastname: Andershed
authors.forename: Henrik
authors.initials: H
authors.lastname: Larsson
mesh_terms: D000293:Adolescent; D000987:Antisocial Personality Disorder / Q000175:diagnosis / Q000523:psychology*; D002648:Child; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D014427:Twins / Q000523:psychology*; D055815:Young Adult