All participants provided informed consent and local research ethics committees or institutional review boards approved the individual studies. Because of the extra perceived vulnerability of the Finnish Crime Study participants, multiple committees (Ethics Committee for Pediatrics, Adolescent Medicine and Psychiatry, Hospital District of Helsinki and Uusimaa, and Criminal Sanctions agency) approved this study(Tiihonen et al., 2015). Except for the Finnish Crime Study, which used a dichotomized outcome measure, all studies employed a continuous scale to increase statistical power(van der Sluis, Posthuma, Nivard, Verhage, & Dolan, 2013). To maximize sample size, we included studies with a broad range of antisocial measures, including both aggressive and non-aggressive domains of ASB, and utilizing study-specific scales in different age groups (see Table 1 and Supplementary Information, Chapter 1). Five large population-based discovery cohorts and three target samples (all subjects were of European descent) were included in this study (see Table 1 for cohort-specific details). The discovery samples comprised 16,400 individuals, while the target samples consisted of 9381 individuals. All participants were recruited from different regions, thus making sample overlap highly unlikely.
