Invalidating adolescents' pro-cannabis opinions: a new tactic of prevention

Background: Attitudes of drug-abstinent youth considering cannabis initiation can be highly ambivalent. Cannabis' positive appeals conflict with fear of detection and physical harm, rendering the balance between initiation and abstinence precarious. Hovland's message-learning theory of attitude change suggests that invalidating the pro-cannabis elements of ambivalent attitudes, which he termed opinions, the building blocks of attitudes, while leaving anti-cannabis opinions intact, may create stronger, less ambivalent, and more resistant anti-cannabis attitudes and lower usage intentions. The usual orientation of seeking or creating weak, ambivalent attitudes makes sense in most contexts, but is of dubious utility in situations where ambivalence already is great. Adding fuel to the fire of ambivalence cannot be useful. Thus, we sought to identify methods selectively invalidating pro-cannabis opinions, to learn the effects of this action on cannabis related attitudes.

Methods: Cannabis-abstinent U.S. middle-school students (N = 101) expressing negative attitudes toward a cannabis-prevention appeal were assigned randomly to one of three conditions designed to invalidate the anti-abstinence opinions that characterized their attitude toward cannabis. They involved either directly personalized threat ("Experts have found only immature people believe as you do"), disconfirmation ("Experts have found your justifications for your response to be deficient"), or an attributional method, where subjects were to list 8 reasons for disliking the ad, but had insufficient time to do so. Following the intervention, subjects watched another ad, and their attitudes toward cannabis and their intentions to use it were assessed.

Results: Analyses tested intervention effects on responses to the second anti-cannabis appeal. Personally threatening messages were found ineffective, and are dismissed from further consideration. However, appeals disconfirming resistant responses significantly decreased ambivalence. Mediational analyses showed that decreased ambivalence resulting from the disconfirming intervention was indirectly associated with less favorable attitudes and, subsequently lower marijuana usage intentions (both p < .01), which have been associated with subsequent behavior.

The attribution-based intervention produced an iatrogenic effect. It increased ambivalence (p < .05), which was associated with more positive usage intentions, which were mediated through positive attitudes (both p < .001).

Conclusions: Our analyses elucidated the role of attitude ambivalence in prevention, providing a more complete understanding of the ways ambivalence can be optimized in preventive persuasion. Findings support methods that invalidate abstinence-resistant opinions, thereby leading to greater susceptibility to subsequent prevention appeals. This approach differs from the usual models in which weak attitudes, whose valence often is attributed to ambivalence, are preferred, on the grounds that weak attitudes are easy to change. Our results do not contest this truism in normal contexts, but adolescent psychotropic substance prevention is not one of these. We suggest a major change in direction, in which ambivalent substance-related attitudes are made less ambivalent through selective invalidation of the pro-drug opinions that constitute the attitude. Rendering such attitudes more negatively unambivalent is the road to successful prevention.