Data were collected over the telephone by trained interviewers. At baseline, a screening to determine zygosity of the twin pair was conducted with one of the twins’ parents and a parental diagnostic interview was scheduled. Interviews with twins were scheduled after obtaining verbal consent (and, for those under the age of 18, consent of parents), as approved by the IRB at Washington University. Wave 3 and 4 assessments were also conducted over the telephone after obtaining verbal consent.
