Ten years later: Locating and interviewing children of drug abusers.

Longitudinal studies require high follow-up rates in order to maintain statistical power, reduce bias, and enhance the generalizability of results. This study reports on locating and survey completion for a 10-year follow-up of the Focus on Families project, an investigation of 130 families headed by parents who were enrolled in methadone treatment for opiate addiction. Despite having no contact with participants in the study for at least 10 years, the project successfully located nearly 99% of parent participants and 98% of their children. Twenty-four percent of the parents and one child had died before the follow-up. Of the surviving sample, 91% of parents and 86% of the children completed the follow-up interview. Multiple techniques were used to locate study participants, including internet searches, researching court and public records, collaborating with government and service agencies, and contacting family and social networks. For more than half of the sample, costly efforts were required to locate individual participants.