Setting and sampling
This study used individual-level data of 15–16-year-old adolescents from the European School Survey Project on Alcohol and Other Drugs (ESPAD), which is a cross-sectional survey that has been performed every fourth year since 1995 in European countries. The results of the surveys are comparable between different countries, as the target population, questionnaires, data collection process, and data entry are standardized (19). In all countries, sampling is based on the school class as the final sampling unit. Questionnaires are anonymous and completed by schoolchildren in a classroom. However, since 2015, countries could opt to participate via an online survey (19).
The present study utilized secondary data from Estonia, Latvia, Lithuania, Finland, and Sweden from 2003, 2007, 2011, and 2015. All data are nationally representative (19–22), except for the data for Latvia in 2015, as the school participation rate in Latvia was low during this year (49% compared to the ESPAD average of 84%), and consequently, the 2015 Latvian sample consisted of a low number of students (1,119 students compared to the ESPAD criterion of 2,400 students) (19).
Measures
Alcohol-related variables
Alcohol use was measured by the question ‘On how many occasions (if any) have you had any alcoholic beverage to drink during the last 30 days?’ The response options were ‘0’, ‘1–2’, ‘3–5’, ‘6–9’, ‘10–19’, ‘20–39’, and ‘40+’. Based on the responses to this question, two groups were formed: 1) adolescents who did not consume alcohol (no) and 2) adolescents who consumed alcohol (yes).
Light alcohol use was assessed based on the following question that was asked separately for four different types of light alcoholic beverages: ‘Think back to last 30 days. On how many occasions (if any) have you had any of the following to drink: beer, cider, alcopops, wine?’ Two groups were formed: 1) adolescents who did not drink any of the types of light alcohol during the last 30 days (no) and 2) adolescents who consumed at least one type of light alcohol during the last 30 days (yes). As no comparable data on light alcohol use were available for 2003, only the results from 2007 to 2015 were used.
Strong alcohol use was measured by the following question: ‘Think back to last 30 days. On how many occasions (if any) have you had any of the following to drink: spirits?’ Based on this question, two groups were formed: 1) adolescents who did not consume strong alcohol (no) and 2) adolescents who consumed strong alcohol (yes).
Study year
The study year referred to the year when the ESPAD survey was conducted: 2003, 2007, 2011, and 2015.
Family-related factors
Family SES was measured based on how adolescents rated their families’ wealth compared to that of other families in the country. Answers were grouped into three categories: 1) better, 2) the same, and 3) worse than that of other families in Estonia.
Family structure referred to completeness of the family. Based on the answers, three groups were formed: 1) living with biological mother and father, 2) living with one biological parent, and 3) living without biological parents.
Rules outside of home indicated how often parents set definite rules about what adolescents could do outside the home. Answers were grouped into three categories: 1) always/often, 2) sometimes, and 3) seldom/never.
Regarding parents’ knowledge about children’s whereabouts on Saturday nights, three categories were formed: 1) always/often know, 2) sometimes know, and 3) usually don’t know.
School-related factors
Skipping school measured whether an adolescent had missed one or more lessons because of skipping or ‘cutting’ school during the last 30 days. Two groups were formed: 1) adolescents who had not missed lessons (no) and 2) adolescents who had missed one or more lessons (yes).
Risk behavior
Smoking referred to whether an adolescent had smoked cigarettes during the last 30 days. Two groups were formed: 1) adolescents who had not smoked (no) and 2) adolescents who had smoked one or more times (yes).
Cannabis use measured whether an adolescent had used marijuana or hashish (cannabis) during the last 30 days. Two groups were formed: 1) adolescents who had not used cannabis (no) and 2) adolescents who had used cannabis one or more times (yes).
Perceived alcohol availability
Perceived alcohol availability was calculated based on five separate questions measuring how difficult an adolescent thought it would be to obtain beer, cider, alcopops, wine, and spirits if they wanted. Answers were divided into three groups: 1) easy, which indicated that the respondent thought it would be easy to obtain at least one of the alcoholic beverages; 2) difficult, which indicated that the respondent thought it would be difficult to obtain all alcohol beverages; and 3) don’t know, which indicated that the respondent did not know how difficult it would be to obtain any of the alcohol beverages.
Statistical analysis
The prevalence of alcohol use, strong alcohol use and light alcohol use was calculated for every study year in all countries. A chi-square test for trend was used to evaluate statistically significant changes in alcohol use over the study period.
Logistic regression analysis was performed to analyze the associations between monthly alcohol use (yes vs no) and gender, study year, family-related factors, school-related factors, risk behavior, and perceived alcohol availability by country. Fully adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were calculated.
The questionnaires of respondents who did not provide answers to questions about the monthly alcohol use were excluded from the analysis (n=767). The final study sample consisted of 57,779 15‒16-year-old adolescents (49.0% boys, 51.0% girls) from Estonia (n=9,559), Latvia (n=8,672), Lithuania (n=12,378), Finland (n=15,889), and Sweden (n=11,281). The questionnaires of respondents who did not provide answers to questions on light or strong alcohol use were excluded from the calculation of the prevalence of light or strong alcohol use (n=417). The questionnaires of respondents who did not provide answers to questions on family-related factors, school-related factors, risk behavior, and perceived alcohol availability questions were excluded from the logistic regression analysis (n=6,394).
Statistical analysis was conducted with Stata 14 (23).