A study conducted in six European countries reveals that children who have strict parents are more likely to smoke cannabis, as well as use tobacco and alcohol. The team, led by the European Institute of Studies on Prevention, observed the relationships between parents and their children in Spain, Sweden, the Czech Republic, the U.K., Slovenia and Portugal to determine what parenting style best prevents drug usage.

Over 7,000 adolescents between 11 and 19 years old were asked if their parents had a more controlling or lenient parental style. The study found that parents who reasoned with their children were most effective in persuading their kids to abstain from drugs.

“Our results support the idea that extremes are not effective: neither authoritarianism nor absence of control and affection,” Amador Calafat, the main author of the study, told the journal Drug and Alcohol Dependence.

Calafat noted that different styles of parenting are helpful in varying situations: when dealing with a child’s school performance, parents who assert low levels of control are the most effective. But, when protecting students from drugs, Calafat asserts that “a good relationship with children” is essential.

Contact us at letters@time.com.