As Young-HUNT data were collected during school hours, the adolescent sample is fairly representative of adolescents in the county, with most non-response resulting from sick leave. Parental response rates were lower. Although people who are struggling with many problems at once, or with very severe problems, seem to be underrepresented in population surveys [56], alcohol use only moderately predicts non-participation in the HUNT study [57]. In addition, simulations have shown that associations between variables are only moderately weakened by high rates of selective non-response [56]. We therefore believe that all consumption groups are adequately represented in the sample, and that it is suited for studying alcohol use within the general population.
