2000 Stories: Victorian Adolescent Health Cohort Study

VAHCS is an eleven-wave cohort study which commenced in August 1992. At baseline, a representative sample of 2032 mid-secondary school adolescents (aged 14–15 years) across Victoria (Australia) were selected, using a two-stage cluster sampling procedure.

At stage one, 45 schools were chosen at random from a stratified frame of government, Catholic, and independent schools, with a probability proportional to the number of students in each educational sector (aged 14–15 years) in the schools in each stratum.

At stage two, a random number table was used to randomly choose one intact class within the year level from each participating school. 6 months later, a second class was randomly chosen from the same schools. One class entered the study in the latter part of the ninth school year (wave 1) and the second class 6 months later (wave two). School retention rates to year nine in Victoria in the year of initial sampling were 98%. One school did not continue beyond wave one, with a loss of 13 participants; thus, 44 schools remained in the study.

Participants were subsequently reviewed at four 6-month intervals during the teenage years (waves three to six), with four follow-up waves in young adulthood at 20–21 years (wave seven), 24–25 years (wave eight), 28–29 years (wave nine), and 34-35 years (wave ten).