study is the Environmental Risk Longitudinal Twin Study (E-risk study) in the United Kingdom. The E-risk study involves data on more than 1000 twin pairs at ages 5, 7, and 12 with the special focus on what factors in the home, family, school, and neighborhood (i.e., environmental risks) promote children's aggression (Moffitt, 2002). The Minnesota Study of Twins and Families (MFTS) is a third major longitudinal twin study that specifically investigates antisocial behavior and substance use across development. MTFS was established in 1989 using same-sexed twin pairs aged 11 or 17. Five hundred additional 11-year-old twin pairs were added in 2000. All twins of those ages, who were born in Minnesota, as identified by birth registry data, were invited to participate. Participants are asked about academic ability, personality, and interests; family and social relationships; mental and physical health; and physiological measurements. Of particular interest are prevalence of psychopathology, substance abuse, divorce, leadership, and other traits and behaviors related to mental and physical health, relationships, and religiosity (Iacono et al., 2006; Keyes et al., 2009).
