Like the original MTFS 11-year-old cohort, the ES sample is being followed every three years, with the age-14 assessment concluded and the age-17 assessment more than half complete. The participation rate for the age-14 assessment exceeds 90%, and we anticipate that age-17 participation will be similarly high. We have just begun a third follow-up at age 20. In addition, DNA samples are currently being collected from all twins and their parents as part of the National Institute on Drug Abuse Genes, Environment, and Development Initiative (GEDI; DA024417), an effort that focuses on the role of the interplay between measured genes and environments in the development of substance use disorders.
