Aims: To study the reliability of adolescents' self-reported drinking and perceived drunkenness in surveys.
Methods: The data from two cross-sectional school-based questionnaire surveys with representative cluster samples (the European School Survey Project on Alcohol and Other Drugs, ESPAD) in Finland were used; there were 2161 (1995) and 3109 (1999) 15-year-old respondents. The response rates were 94% and 90% respectively. The measurements analysed were an open-ended and a set of closed-category questions concerning the latest drinking occasion.
Results: The set of three closed questions used in 1995 yielded mean amounts of 6.6 (girls) and 8.7 (boys) centilitres of pure alcohol whereas the figures obtained from the open question were 8.5 (girls) and 11.8 (boys) centilitres. With the closed set extended in 1999 into five questions, the two figures among girls were 7.7 (closed) and 7.7 (open) centilitres; the corresponding figures among boys were 11.3 (closed) and 11.7 (open) centilitres. Individual level correlations between the two measures among girls were 0.69 in 1995 and 0.69 in 1999; and 0.69 (1995) and 0.65 (1999) among boys. The numbers of students reporting specific beverage type use were higher when using closed questions compared with an open question. Drunkenness self-reports related logically to amounts of alcohol drunk.
Conclusions: The adolescent drinking amount self-reports seem reasonably reliable and valid both on a population and individual level. A set of closed questions may capture the amount drunk even better than an open question.