Behavioral problems in teenagers partially explain why children who experienced trauma are more likely to smoke, use drugs, and eat unhealthy foods, according to a 2026 study of 4,229 Brazilian youth. Gram Research analysis shows that externalizing problems like aggression increased substance use odds by 2 to 3 percent for each increase in behavioral severity. Surprisingly, these same behavioral problems also led some youth to exercise more, revealing a complex relationship between trauma, mental health, and health behaviors.
A new study of over 4,000 Brazilian young people reveals how childhood trauma can lead to risky health behaviors like smoking, drug use, and poor eating habits. The research shows that mental health problems, especially behavioral issues, act as a bridge between trauma and these unhealthy choices. Interestingly, some behavioral problems also pushed teens to exercise more, suggesting the relationship between trauma and health is complicated. Understanding these connections could help doctors and counselors create better programs to protect young people who have experienced trauma.
Key Statistics
A 2026 cohort study of 4,229 Brazilian youth found that behavioral problems mediated the relationship between childhood trauma and smoking, with odds of smoking increasing by 2 to 3 percent for each increase in externalizing problem severity.
According to a 2026 analysis of 4,229 young people followed from birth to age 18, behavioral problems explained why traumatized youth consumed more ultra-processed foods, with a standardized effect size of 0.12.
A 2026 Brazilian birth cohort study of 4,229 participants revealed an unexpected finding: behavioral problems associated with childhood trauma also increased physical activity levels, with effect sizes ranging from 0.10 to 0.30.
In a 2026 study tracking 4,229 Brazilian youth, anxiety and depression did not explain the link between childhood trauma and health risk behaviors, suggesting that behavioral problems, not mood problems, drive the trauma-to-unhealthy-behavior pathway.
The Quick Take
- What they studied: Whether mental health problems explain why kids who experience trauma end up making unhealthy choices like smoking, using drugs, eating junk food, and being inactive.
- Who participated: 4,229 young people born in 2004 in Pelotas, Brazil, who were followed from childhood through age 18. Researchers tracked their trauma exposure, mental health, and health behaviors over time.
- Key finding: Behavioral and emotional problems in teens partially explained why traumatized children were more likely to smoke, use drugs, and eat ultra-processed foods. Surprisingly, some behavioral problems also led to more physical activity.
- What it means for you: If you or someone you know experienced childhood trauma, getting mental health support early could help prevent unhealthy coping behaviors. However, this research is from one country and may not apply equally to all populations.
The Research Details
This study followed the same group of Brazilian children from birth through age 18, collecting information at different time points. Researchers asked caregivers about traumatic events the children experienced up to age 11, such as abuse, neglect, or witnessing violence. At age 15, they used a questionnaire to measure mental health problems, dividing them into two types: internalizing problems (like anxiety and depression) and externalizing problems (like aggression and rule-breaking). At age 18, they measured health risk behaviors including smoking, alcohol use, drug use, junk food consumption, and physical activity using both questionnaires and activity trackers.
The researchers used a statistical method called counterfactual mediation analysis to figure out whether mental health problems were the reason trauma led to unhealthy behaviors. This approach is like asking: if we could remove the mental health problems but keep the trauma, would the unhealthy behaviors still happen? This helps identify the actual pathway from trauma to risky choices.
Following the same people over many years is stronger than just comparing different groups at one point in time. This design shows cause and effect more clearly. By measuring trauma early and health behaviors later, researchers could be more confident that trauma came first and caused the problems, not the other way around. Testing this in a low- or middle-income country like Brazil is important because most research on this topic comes from wealthy countries.
This study has several strengths: it tracked real people over many years, used validated questionnaires to measure mental health, and included a large sample size. However, the study relied on caregiver reports of trauma, which might miss some experiences. The researchers also couldn’t measure all possible confounding factors that might affect the results. The study was conducted in Brazil, so findings may not apply equally to other countries or cultures.
What the Results Show
The study found that behavioral problems, such as aggression and rule-breaking, partially explained why traumatized youth were more likely to smoke and use illegal drugs. For every increase in behavioral problems, the odds of smoking increased by 2 to 3 percent, and the odds of drug use also increased by 2 to 3 percent. Behavioral problems also explained why traumatized youth ate more ultra-processed foods. Interestingly, anxiety and depression (internalizing problems) did not explain the link between trauma and unhealthy behaviors, which was surprising to researchers.
One unexpected finding was that behavioral problems actually increased physical activity in some cases. Youth with more behavioral problems were more physically active than those without such problems, even when they had experienced trauma. This suggests that behavioral problems might push some young people to be more active, possibly as a way to release energy or cope with stress.
When researchers looked at smoking and drug use together, they found that both internalizing and externalizing problems combined played a role in explaining why traumatized youth engaged in these behaviors. However, when examined separately, only externalizing problems showed clear effects.
The study revealed that the pathway from trauma to unhealthy behaviors is not straightforward. While behavioral problems increased substance use and junk food consumption, they also increased physical activity in some youth. This suggests that the same behavioral problems might have both protective and harmful effects depending on how they are expressed. The research also showed that anxiety and depression, despite being common in traumatized youth, did not explain the connection between trauma and the specific health risk behaviors measured in this study.
According to Gram Research analysis, this study adds important evidence from a low- and middle-income country, as most previous research on trauma and health behaviors comes from wealthy nations. Earlier studies suggested that mental health problems should mediate the link between trauma and unhealthy behaviors, but this study shows the picture is more complex. The finding that behavioral problems increase physical activity contradicts some previous assumptions that all mental health problems lead to sedentary lifestyles. This research highlights that the relationship between trauma, mental health, and health behaviors varies by type of mental health problem.
The study relied on caregivers to report childhood trauma, which may have missed some experiences or been influenced by memory. Researchers could not measure all factors that might affect the results, such as socioeconomic status changes or other stressful life events after age 11. The study was conducted in Brazil, so results may not apply to youth in other countries with different cultures and healthcare systems. Physical activity was measured using accelerometers in only some participants, which could affect those results. The study also could not determine why behavioral problems sometimes increased physical activity, leaving that finding unexplained.
The Bottom Line
Young people who have experienced trauma should have access to mental health support, particularly programs that address behavioral problems like aggression and rule-breaking. Schools and healthcare providers should screen for both trauma exposure and behavioral issues in youth. Prevention programs should focus on teaching healthy coping skills and stress management. These recommendations are based on solid evidence from a large, long-term study, though more research in different populations is needed.
Parents, teachers, school counselors, and healthcare providers working with youth should care about these findings, especially those in communities where trauma is common. Young people who have experienced trauma or who notice behavioral changes in themselves or friends should seek support. This research is particularly relevant for professionals in low- and middle-income countries where resources for mental health support may be limited. However, these findings are from one country and may not apply equally to all populations.
Mental health problems typically develop gradually over months to years after trauma exposure. Changes in health behaviors may take several months to years to develop. Improvements from mental health treatment may take weeks to months to show effects on health behaviors. Long-term benefits of addressing behavioral problems early could prevent serious health problems in adulthood.
Frequently Asked Questions
Does childhood trauma directly cause unhealthy behaviors like smoking and drug use?
Childhood trauma increases risk for unhealthy behaviors, but not directly. A 2026 study of 4,229 youth found that behavioral problems like aggression act as the bridge between trauma and substance use, increasing smoking and drug use odds by 2 to 3 percent per increase in behavioral severity.
Can anxiety and depression from childhood trauma lead to unhealthy eating and smoking?
Surprisingly, no. A 2026 Brazilian cohort study found that anxiety and depression did not explain why traumatized youth smoked more or ate junk food. Instead, behavioral problems like aggression and rule-breaking were the key mental health factors driving these unhealthy choices.
Does getting mental health treatment for trauma help prevent unhealthy behaviors in teens?
This study suggests it could help, particularly treatment addressing behavioral problems. Since behavioral issues mediate the trauma-to-unhealthy-behavior pathway, treating aggression and rule-breaking may reduce smoking, drug use, and junk food consumption in traumatized youth.
Why do some traumatized teens with behavioral problems exercise more?
A 2026 study of 4,229 youth found that behavioral problems increased physical activity, suggesting some youth may channel aggressive impulses or stress into exercise. This shows the same behavioral problems can have both protective and harmful health effects depending on how they are expressed.
Is this research applicable to teenagers in my country?
This study was conducted in Brazil with Brazilian youth, so results may not apply equally to other countries with different cultures and healthcare systems. More research in diverse populations is needed to confirm whether these patterns hold worldwide.
Want to Apply This Research?
- Track weekly behavioral patterns and mood changes alongside health habits. Log instances of aggressive or rule-breaking thoughts, anxiety levels, and corresponding health choices (smoking, food choices, physical activity) to identify personal patterns between mental state and health behaviors.
- Use the app to set reminders for healthy coping strategies when behavioral or emotional problems arise. Create a personal action plan that redirects aggressive impulses or stress toward physical activity. Set daily goals for reducing ultra-processed foods and increasing movement, with check-ins tied to mood tracking.
- Review monthly patterns to identify which mental health triggers lead to which unhealthy behaviors. Track progress on reducing substance use and junk food while maintaining or increasing physical activity. Share trends with a healthcare provider or counselor to adjust coping strategies as needed.
This research describes associations between childhood trauma, mental health, and health behaviors in a Brazilian population and should not be used for self-diagnosis or self-treatment. If you or someone you know has experienced trauma or is struggling with mental health or substance use, please consult a qualified healthcare provider, mental health professional, or contact a crisis helpline. This study does not provide medical advice and is intended for educational purposes only. Individual circumstances vary, and professional guidance is essential for proper assessment and treatment.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.