Methods and definitions

Data presented in the schools survey tables are derived mainly from the ESPAD schools survey project and the HBSC (WHO) Schools Survey: Health behaviour in school-aged children. Participation in both surveys, each conducted every four years, has grown in each round and includes both EU Member States and non-EU countries with over 20 EU Member States participating in the most recent surveys together with Bulgaria, Croatia, Norway, Romania and Turkey in the ESPAD survey. In addition, annual, or biennial, national schools surveys are conducted in Spain, Italy, Portugal and Sweden and regional surveys are conducted in the UK and Belgium.

The international comparability of the ESPAD schools survey is based on nationally representative samples of school classes with the goal of having at least 2400 participating students from the target group, and by standardising the target age group (between 15 and 16 years), the questionnaire, data collection in schools, assurance of anonymity and the time of year that data collection takes place. Cautions are recommended regarding some data in specific countries: comments on these are found in the methodological information sections found on and in published reports – ESPAD (The European School Survey Project on Alcohol and Other Drugs) 1995, 1999 and 2003 by The Swedish Council for Information on Alcohol and Other Drugs (CAN) and Council of Europe (Pompidou Group).

The HBSC (WHO) Health behaviour in school-aged children included for the first time in the 2001/2002 surveys questions about cannabis use. International comparability is based on standardisation by target age group (mean age 15.5), cluster sampling methods with the goal of more than 1500 participating students from the target group, questions about cannabis based on the ESPAD survey questionnaire, data collection in the schools, and assurance of anonymity. As with ESPAD, cautions are recommended regarding some data in specific countries. Descriptions of the study are found on and in ‘Young people’s health in context. Health Behaviour in School-aged Children (HBSC) study: international report from the 2001/2002 survey’ Edited by: Candace Currie, Chris Roberts, Antony Morgan, Rebecca Smith, Wolfgang Settertobulte, Oddrun Samdal and Vivian Barnekow Rasmussen, eds. (2004) Health Policy for Children and Adolescents, No. 4, 2004, ISBN 92 890 1372 9.

National schools surveys conducted in Belgium, Spain, Italy, Portugal, Sweden and UK are largely comparable with ESPAD and HBSC surveys in terms of sampling, 15/16-year-old age groups, the questionnaire, data collection in schools, and assurance of anonymity. Overall the comparisons made between ESPAD data and other school surveys (in three countries – Norway, Sweden and the Netherlands – as well as comparisons between ESPAD and the HBSC surveys) show very similar figures. However in other countries, differences in methods for achieving prevalence estimates means that caution is necessary with regard to making direct comparisons between some of these surveys.