3. In the 1980s, First Lady Nancy Reagan initiated an antidrug campaign toward school-age children called Just Say No! The campaign consisted of speeches and rallies, television commercials, and school-based programs. During the 1980s and early 1990s when this campaign was in effect, the use of alcohol and marijuana among older children and adolescents decreased. Why can’t we conclude that the Just Say No!

campaign caused this reduction in substance use?