A common genetic factor explains the association between psychopathic personality and antisocial behavior HENRIK LARSSON 1 #, CATHERINE TUVBLAD 2 *#, FRUHLING V. RIJSDIJK 1 , HENRIK ANDERSHED 3 , MARTIN GRANN 4, 5 AND PAUL LICHTENSTEIN 2 1 Social, Genetic, and Developmental Psychiatry Research Centre, Institute of Psychiatry, King’s College London, UK ; 2 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Sweden ; 3 Department of Behavioral, Social, and Legal Sciences, O ¨ rebro University, Sweden ; 4 Centre for Violence Prevention, Karolinska Institutet, Sweden ; 5 Swedish Prison and Probation Service, Sweden ABSTRACT Background. Both psychopathic personality traits and antisocial behavior are influenced by genetic as well as environmental factors. However, little is known about how genetic and environmental factors contribute to the associations between the psychopathic personality traits and antisocial behavior. Method. Data were drawn from a longitudinal population-based twin sample including all 1480 twin pairs born in Sweden between May 1985 and December 1986. The twins responded to mailed self-report questionnaires at two occasions: 1999 (twins 13–14 years old), and 2002 (twins 16–17 years old). Results. A common genetic factor loaded substantially on both psychopathic personality traits and antisocial behavior, whereas a common shared environmental factor loaded exclusively on antisocial behavior. Conclusions. The genetic overlap between psychopathic personality traits and antisocial behavior may reflect a genetic vulnerability to externalizing psychopathology. The finding of shared en- vironmental influences only in antisocial behavior suggests an etiological distinction between psychopathic personality dimensions and antisocial behavior. Knowledge about temperamental correlates to antisocial behavior is important for identification of susceptibility genes, as well as for possible prevention through identification of at-risk children early in life. INTRODUCTION Psychopathy is a serious personality disorder defined by callous and unemotional affects, a grandiose and manipulative interpersonal style, and pervasive impulsive and irresponsible be- havior (Cleckley, 1941 ; Hare, 2003). Psycho- pathic personality disorder has been linked to antisocial behavior in adults (Hare et al. 2000; Hare, 2002). A better understanding of the etiology underlying the personality profile in- volved in severe antisocial behavior is important for the identification of effective intervention targets. How to best conceptualize psychopathy and how many symptom dimensions that best de- scribes the disorder is yet unresolved (Cooke & Michie, 2001 ; Hare, 2003 ; Cooke et al. 2004). Factor analysis of psychopathic traits have found two (e.g. Hare, 1991; Lilienfeld & Andrews, 1996 ; Frick et al. 2000 ; Benning et al. 2003), three (Cooke & Michie, 2001 ; Andershed * Address for correspondence : Dr Catherine Tuvblad, De- partment of Medical Epidemiology and Biostatistics, Karolinska Institutet, PO Box 281, SE-171 77 Stockholm, Sweden. (Email : Catherine.Tuvblad@ki.se) # These authors contributed equally to this work. Psychological Medicine, 2007, 37, 15–26. f 2006 Cambridge University Press doi:10.1017/S003329170600907X First published online 19 October 2006 Printed in the United Kingdom 15