Parental externalizing disorder data were available for 435 (96%) of the mothers and 326 (72%) of the fathers of prospective participants. We used a 3-category parental externalizing disorder history measure. Those for whom either parent had externalizing disorder diagnosis [352 (77%); of these, 151 (33%) had two affected parents, 87 (19%) only the father was affected/known to be affected, and 114 (25%) only the mother was affected/known to be affected)] were set as the reference group and were compared to those for whom neither parent had an externalizing disorder diagnosis [47 (10%)] and those for whom there were incomplete parental externalizing disorder history information (i.e., one parent was unaffected and the other parent was missing externalizing disorder data) [55 (12%)].
