Institutional diffusion. The presence of advertisements (or other intervention messages) can produce a broad response among public institutions (such as school boards, state legislatures, and the media). In turn, these institutions may initiate health policies or programs that affect cognitions and social expectations of the targeted audience. Thus, an antidrug communication intervention may stimulate concern among school board members about drug use and lead them to allocate more school time to drug education. Religious, athletic, and other private youth organizations may increase their antidrug activities. News organizations may cover drug issues more actively, and the nature of their messages may change. Movies, music, or entertainment television may change their level of attention to, and the content of, drug-related messages. Like the social diffusion route, institutional diffusion does not require an individual-level association between message exposure and beliefs or behavior change. This path of influence can be seen at the level of community analysis. Also, institutional diffusion can be a slow process, and there might be a relatively long lag between exposure to aspects of the communication intervention and institutional response and an even longer lag until the effects on audience beliefs or behavior become apparent.
Each of the five models of communication effects described represents a complementary process through which a health communication intervention might influence underlying beliefs and behavior. Any one of these models may describe the actual path of effect, or all of them may describe paths of effect that occurred. One important implication of these models is that they suggest that very different strategies may be necessary for evaluating the effectiveness of a given health communication intervention. Models of immediate, delayed, or generalized learning suggest that evaluating message (or campaign) effectiveness by comparing individuals who have or have not been exposed is appropriate. These models differ, however, in that they suggest that the evaluation of campaign effects should focus on different outcomes or on different time frames.