The CHDS has run for over 40 years. During this time, the study team have followed the health, education, and life progress of a group of 1,265 children born in the Christchurch (New Zealand) urban region in mid-1977. Members of this cohort have now been assessed at birth, 4 months, 1 year, on annual intervals to age 16, at 18 and at 21. At the beginning of the cohort, 635 male and 630 female participants were involved in this study. Of these, 11.2% were of Māori ethnicity, 2.9% were of Pacific ethnicity, and 85.9% were of New Zealand European/‘other’ ethnicity.