At age 7 information on the twins is collected from both parents and targets the development of emotional and behavior problems, as assessed by the Child Behavior Checklist 6-18 (CBCL). From 2001 onwards, the Conners’ Parent Rating Scale — Revised (CPRS-R) was also included. In addition, these surveys included items on zygosity, medical conditions, vaccinations, tonsillectomy (from 2005), demographic characteristics, growth, sport and leisure activity of both children and parents, and additional items on well-being (from 2010). In 2017 the survey has been considerably shortened (for example the Conners was removed).

Subject age
  • 7.0 years
Time span From 1995-01-01 (ongoing)
Geographic location NL
Dorret I. Boomsma
Vrije Universiteit Amsterdam
YNTR administration
Vrije Universiteit Amsterdam
Funding information
Sophia Foundation SSWO
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