International Youth Development Study (IYDS)

The International Youth Development Study (IYDS) is a long-term study that looks at the development of healthy and problem behaviours among young people in the state of Victoria, Australia and the state of Washington, United States.

IYDS is one of the first studies designed to examine whether or not differences in Australian and American cultures and schools affect youth development. The study began in 2002. The original sample included approximately 1000 students at each of three year levels in both Victoria and Washington, giving a total of nearly 6000 participants. The study continues to follow-up participants into adulthood.

Study Summary
Study name International Youth Development Study
Study abbreviation IYDS
Current principal investigator/s John Toumbourou
Richard Catalano
Sheryl Hemphill
Current project manager

Rachel Smith

Primary Institution/s Centre for Adolescent Health
Collaborating Institution/s Social Development Research Group, University of Washington
Australian Catholic University
Deakin University
Major funding source/s National Health and Medical Research Council - NHMRC
Australian Research Council - ARC
Study website
Key reference for study McMorris, B.J., Hemphill, S.A., Toumbourou, J.W., Catalano, R.F. and Patton, G.C. (2007). Prevalence of substance use and delinquent behavior in adolescents from Victoria, Australia and Washington State, United States. Health Education and Behavior, 34: 634-650
Study focus

Risk and protective factors, as well as healthy and problem behaviours in young people including substance use, delinquency, violence, risky sex, depression and self-harm

Sampling frame

In 2002, a two-stage cluster sample design was used to recruit students in both states (Victoria, Australia and Washington State, USA). In the first stage, schools were selected at random, based on a probability proportional to grade-level size from a stratified sampling frame of all schools in Victoria (government, Catholic and independent) and Washington (public, private and alternative). At Stage 2, single intact classes from each school for the selected grade level (Grade 5, 7, or 9) were chosen at random; in a few cases, 2 classes from different year levels were randomly chosen at a school

Primary study type Longitudinal cohort
Primary participant (at recruitment) Index child
Year commenced


Is this study ongoing? Yes - the study is ongoing
Ongoing recruitment? No
Sample size (N)

5769 participants were recruited in total, including 2884 Australian participants and 2885 USA participants

Survey data available? Yes
Imaging data available? No
Linkage to administrative dataset/s? No, no consent to link to administrative dataset(s) obtained
Biosamples available? No
Are data available to others outside study team, with appropriate safeguards and structures in line with the cohort’s ethics and governance processes? Yes
Are there any costs associated with data/sample access for approved requests? There are usually no costs associated with access
Broadest type of participant consent available Specific consent (can be used for this project only)
Wave Year Age Sample size (N)
1 2002 9-16 years N(Total)=2884
2 2003 11-17 years N(Total)=2884
3 2004 11-16 years N(Total)=1909
4 2006 14-16 years N(Total)=927
5 2007 15-17 years N(Total)=927
6 2008 16-18 years N(Total)=926
F1 2010 17-24 years N(Total)=2872
F2 2012 20-26 years N(Total)=2871
F3 2014 22-28 years N(Total)=2870
Study Contacts
Principal investigator/s John Toumbourou
Richard Catalano
Sheryl Hemphill
Project manager

Rachel Smith

Study Contact

Phone: 1 800 200 141
Address: Centre for Adolescent Health, Level 2 East
Murdoch Children's Research Institute,
Royal Children’s Hospital
Flemington Road, Parkville
Victoria 3052 Australia