Validity and reliability of a high school drug use questionnaire among Mexican students.

This study was carried out to ascertain the validity and reliability of data generated through an internationally developed self-administered questionnaire. Data were collected from two student populations in which prevalence of drug use was known (high and low prevalence rates) and information obtained from the questionnaire checked through personal interview. The questionnaire covered both demographic characteristics and drug use items. A total of 474 students were tested and 335 students (70.7 per cent) retested. Although percentages of missing data and inconsistent responses were high, the questionnaire appeared valid and reliable when analysed on a group basis. It was less reliable on an individual basis. In conclusion, it is considered that with minor modifications the questionnaire can be used in the populations studied with enough confidence in validity and reliability to allow comparisons.