This paper tested an interactive model of attitudes and perceived social support in a panel of substance use among Irish post-primary students. The paper hypothesises was that contingent consistency interactions would be more likely (1) for perceived social support form friends than from parents; (2) for perceived substance use by others than for verbal support; (3) in predicting change than in predicting current substance use; (4) for younger than older adolescents; and (5) for drug use than for drinking and smoking.

Contrary to predictions, the authors found significant contingent consistency interactions for all three behaviours and regardless of the age of the students. These interactions were more likely when predicting current behaviour rather than behaviour change. The significant interactions primarily involved perceived substance use by friends. Increased accessibility, selective friendship choices, and rationalization processes are possible explanations for the findings.