This report is follow-up to the authors' 1986 report Smoking, Drinking and Other Drug Use Among Dublin Post-primary School Pupils, which focussed on the prevalence of use of these substances, and the factors associated with use. In this study, the author's objectives were to examine the influences that bring about initiation to the substances, and changes in level of use. They said that because the previous study was cross-sectional in design, it was not possible to distinguish between events that came about as a result of substance use and those that bring about such use. Thus, this final phase of the survey used a longitudinal design rather than a cross-sectional design. It involved a random sample of over 2,000 post-primary pupils, who responded anonymously to a questionnaire. The information was matched with the earlier phases of the project, using a computer-matching procedure, and the cohorts were compared. For smoking, it was found that the strong relationship between reported smoking and friends smoking was due to selective friendships that derived from, rather than were causes of, smoking. Among girls, it was found that the younger cohort was smoking more at an earlier age.

It was found that, for drinking, the younger cohort reported higher levels of frequency of being drunk for each age level. In terms of illegal drug use, it was found that there was no indication of any difference between the older and younger cohorts for either current drug use or for lifetime prevalence. Peer approval and peer example were found to be important predictors for the use of illegal drugs by girls, while peer example emerged as important for boys.