Abstract
With the increase in substance use by young people in recent years, there has been a growth in evidence‐based programs aimed at preventing this problem. This study aims to assess possible changes in family and parental dynamics among families taking part in a short (6‐session) universal program. These changes might act as protective factors for families in preventing substance use. A quasi‐experimental design was used, with pretest and posttest evaluations. The participating schools meeting the inclusion criteria were randomly assigned to the experimental or control group. The sample was made up of 16 experimental groups and 17 control groups, with the participation of 353 parents and 289 youths. The results confirm the strengthening of the families by improving the following key components of parenting: resilience, involvement, family conflicts, and positive parenting. Reinforcing parenting skills through a short program is a good strategy to take, ensuring high levels of adherence (86.40% retention of the initial sample). Hence future universal prevention programs must not just set their sights on high levels of effectiveness, but also on efficiency.