One hypothesis is that early drinking is a direct risk factor for the development of alcoholism. Dr. DeWit et al. interpreted their results as representing a causal process, viz., "The results demonstrate that prevention programs that are effective in delaying alcohol use until age 15 or 16 or later will avert substantial alcohol-related harm in later life" (p. 749). An alternative hypothesis is that early drinking and alcoholism are both manifestations of a general vulnerability to problem behaviors but are not causally related. On the basis of this model, interventions designed simply to delay alcohol use would not modify the underlying vulnerability that predisposes at-risk individuals to problem outcomes, such as alcoholism.