Substance use is transmitted across generations, but it is not inevitable
A new study published in the scientific journal Addictive Behaviors confirms what many have feared: adolescents who grow up in households where parents use alcohol or other drugs face a higher probability of using substances themselves. When parents are alcohol users, the probability of their child drinking is 24 per cent more than if parents dont drink. When parents use multiple substances, the probability of their child doing the same rises to 28 per cent.
– This is not destiny, but a risk gradient. And what we found is that the way parents raise their children can significantly disrupt that transmission, says Professor Dr. Zila Sanchez, Head of the Department of Preventive Medicine at the Federal University of São Paulo in Brazil and lead author of the study.
The study is part of PREV.ACTION, a larger community-based randomised trial conducted across four municipalities in São Paulo. The project is funded by the Research Council of Norway with close to NOK 10 million, as well as by the São Paulo Research Foundation (FAPESP). Total funding across both sources exceeds NOK 13 million.
Professor Hugo Cogo Moreira at the Faculty of teacher education and languages at Østfold University of Applied Sciences is the project lead on the Norwegian side and a co-author of the study.
The strongest finding: abstinence is the most powerful signal
Perhaps the most striking single finding in the study was this: when parents themselves use no substances, no alcohol, no tobacco, no cannabis, 89 per cent of their adolescent children are also substance-free. That was the strongest single association in the entire analysis.
– It tells us that what parents do matters at least as much as what they say, Sanchez emphasises.
More than half of the adolescents in the study had never used any substance at all – even in samples from communities with relatively high levels of parental substance use. This points to the power of protective factors, and to the fact that those factors can be deliberately strengthened.
Four parenting styles, one stands out
The study draws on four parenting styles defined along two dimensions: how much warmth and emotional connection parents show, and how much monitoring and structure they provide.
The authoritative style, high on both dimensions, emerges as by far the most protective. These are parents who are engaged and affectionate, while also setting and maintaining clear expectations.
– In everyday life, it looks like a parent who knows where their child is after school, who they spend time with, what they are worried about. At the same time, it is a parent who sets and enforces clear rules, about curfews, about alcohol, without being punitive. It is the combination of ‘I care about you’ and ‘I have expectations for you’ that seems to matter, Sanchez explains.
The authoritarian style, high control, low warmth, showed some protective effect against drug use, but not against alcohol. One interpretation is that strict control without an emotional foundation may suppress certain behaviours while creating a tension that, in the case of alcohol specifically, opens another door. Alcohol is more normalised in Brazilian culture than other drugs, and its social pathways are harder to block through control alone.
What can parents concretely do?
Sanchez points to three things that stand out clearly from the research findings:
- Maintain a close and open relationship with your child, be someone they can talk to.
- Set clear and consistent rules about substance use, including alcohol. S
- Stay involved in their daily life, know their friends, know their routines.
– Knowing where your child is and who they are with has consistent evidence behind it and does not require major changes. A simple daily check-in, genuine curiosity about their friendships, these habits, maintained consistently, are associated with real protective effects, she says.
She also warns against treating alcohol at home as something trivial or inevitable:
– Even parents who otherwise have a good relationship with their children showed a residual association between their own drinking and their children’s. Normalising alcohol at home, regular use at meals, always having it available, is a risk factor regardless of parenting quality.
The prevention window opens earlier than most parents expect
The study points to a prevention window that arrives sooner than most parents anticipate. In Brazil, where more than half the population tried alcohol for the first time before the age of 18, initiation is already underway in a significant proportion of adolescents by the age of 14 or 15.
– The preventive foundation needs to be built before that. Parenting styles are not things you switch on at age 13; they reflect patterns established over years, Sanchez emphasises.
Relevance beyond Brazil
The study was conducted in Brazil, but Sanchez believes the underlying mechanisms are likely to apply broadly:
– The basic mechanisms, parental modelling, the protective role of authoritative parenting, the importance of monitoring, have been documented in many countries with different cultural profiles. The specific numbers, the normalisation of alcohol, the cultural weight of certain substances, those will vary. But the protective function of parenting quality appears to be robust across contexts.
About the article
Sanchez, Z., Caetano, S., Valente, J. Y., Soares-Santos, L. E., & Cogo-Moreira, H. (2026). Does the apple fall far from the tree? When parenting styles disrupt the intergenerational pattern of substance use. Addictive Behaviors, 174, 108567. https://doi.org/10.1016/j.addbeh.2025.108567
About the PREV.ACTION project and Østfold University of Applied Sciences
This article is part of PREV.ACTION, a broader research project in which the team is now implementing a multicomponent intervention, school-based prevention, family programmes, and environmental strategies and following adolescents over time. The aim is to test whether the protective factors identified in this study translate into actual reductions in substance use initiation.
Professor Hugo Cogo Moreira at Østfold University of Applied Sciences leads the project on the Norwegian side. Norwegian research funding also covers the implementation of the intervention package in Mozambique, where knowledge from Brazil is being gradually transferred and adapted to a different context. Results from the full project are expected in 2027.
- Relevant article: Millioner til å forske på reduksjon av alkoholforbruk hos ungdom (Arcive article hiof.no)
- About the study in Fredriksstad Blad: Knuser myter om ungdommers alkoholbruk (for subscribers)
About Professor Dr. Zila Sanchez
Zila M. Sanchez is Head of the Department of Preventive Medicine at the Federal University of São Paulo (UNIFESP), Brazil. She is Editor-in-Chief of the Journal of Prevention (Springer Nature), serves on the board of the European Society for Prevention Research (EUSPR), and is a member of the WHO Technical Advisory Group on Alcohol and Drug Epidemiology. She has authored more than 200 peer-reviewed publications and has advised WHO, PAHO, UNODC and UNDP.