mothers of the offspring. Offspring were eligible to participate if the twin gave permission to contact them (Project 1, but not Project 2, also required permission from the mother before contacting offspring). Experienced staff from the Institute for Survey Research (ISR) at Temple University conducted all data collection. Participants gave verbal consent prior to being interviewed and parents provided written consent for their minor aged offspring to be interviewed. All study procedures were approved by the Institutional Review Board at the participating institutions.
