Waller, Rebecca et al. Journal of the American Academy of Child & Adolescent Psychiatry , Volume 57 , Issue 12 , 955 – 963

This study of over 200 twin pairs, in line with the findings of Henry et al., shows that parenting harshness is related to childhood callous unemotional traits and aggression over and above genetically-mediated effects. Effects were not mediated by child age, sex or family income.