Moreover, only about a 1/3 of the parents attended more than half of the parent training workshops. We are aware of the substantial benefits reported in the literature with respect to family-based substance abuse preventive interventions. However, what is often overlooked in these reports is that the control group only includes those parents who were willing to participate in the intervention if assigned to it. In our study, parents only had to agree to their child being assessed and not to their participation in the interventions. As a consequence, the control group in our study includes a much larger proportion of the population denominator (that is, those who were eligible to participate) than what is seen in the typical family-based preventive intervention trials.
