The definition of “environmental risk” varies widely among replication attempts. Although many studies include only cases of physical abuse or neglect in their “risk” category (Huang et al., 2004; Huizinga et al., 2006; Weder et al., 2009; Widom & Brzustowicz, 2006; Young et al., 2006), others have included social indicators as risk factors, such as the child’s residence type (single or multi-family, rented vs. owned, (Nilsson et al., 2006)); a variety of “early traumatic life events” which included whether a parent was absent for extended periods, parental mental health, and physical handicaps (Frazzetto et al., 2007); still another constructed a life history scale including information on family structure, education, and social status (Reif et al., 2007).
