Researchers studied 351 children to understand why some kids with ADHD also develop oppositional defiant disorder (ODD), a condition where children are persistently angry, defiant, and argumentative. The study looked at thinking skills, behavior patterns, and blood markers like vitamin D and thyroid hormones. They found that behavior problems—especially conduct issues and impulsivity—were the main factors linked to ODD in children with ADHD. Interestingly, thinking ability and the blood markers tested didn’t seem to play a major role. This suggests that behavioral interventions targeting conduct problems might be the most helpful approach for these children.

The Quick Take

  • What they studied: What causes some children with ADHD to also develop oppositional defiant disorder (ODD), which makes kids more defiant and angry
  • Who participated: 351 children ages 6-12 years old, divided into three groups: kids with only ADHD, kids with both ADHD and ODD, and kids without either condition
  • Key finding: Children with both ADHD and ODD showed much worse behavior problems, especially conduct issues and trouble controlling impulses. Behavior problems were the strongest predictor of ODD symptoms, while thinking ability and blood markers (vitamin D and thyroid hormones) didn’t seem to matter much
  • What it means for you: If your child has ADHD and shows signs of defiance or conduct problems, focusing on behavioral strategies and interventions to address these specific behaviors may be more helpful than looking for physical causes. Talk to your doctor about behavior-focused treatment options.

The Research Details

This was a cross-sectional study, which means researchers looked at all the children at one point in time rather than following them over months or years. They divided 351 children into three groups: those with ADHD only, those with both ADHD and ODD, and a control group of typically developing children without either condition.

Each child was tested in three main areas. First, researchers measured thinking and learning abilities using a standard intelligence test. Second, they asked parents to rate their child’s behavior using two well-known questionnaires that measure attention problems, hyperactivity, and conduct issues. Third, they took blood samples to check vitamin D levels and thyroid hormone levels, which can sometimes affect behavior and mood.

The researchers then compared the three groups to see which factors were most different between them and which factors best predicted ODD symptoms in children with ADHD.

This approach is important because it helps identify which factors actually matter when children have both ADHD and ODD. By testing cognitive, behavioral, and physical factors all at once, researchers could determine which ones are truly connected to the development of ODD. This helps doctors and parents focus on the most effective treatments rather than wasting time on factors that don’t actually contribute to the problem.

This study has several strengths: it included a reasonably large sample of 351 children, used well-established and validated assessment tools that are widely used in clinical practice, and included a control group for comparison. However, because it’s a cross-sectional study (snapshot in time), it can’t prove that behavior problems actually cause ODD—only that they’re connected. The study also relied on parent reports for behavior, which can sometimes be biased. Additionally, the study only measured a few blood markers, so other physical factors weren’t explored.

What the Results Show

The most important finding was that children with both ADHD and ODD had significantly more severe behavior problems compared to children with ADHD alone. These problems included conduct issues (like aggression or rule-breaking), impulsivity (acting without thinking), and difficulty managing emotions. When researchers looked at what predicted ODD symptoms, conduct problems emerged as the strongest factor, meaning kids with more conduct problems were much more likely to have ODD.

Hyperactivity was also identified as an important predictor, suggesting that the combination of hyperactivity and conduct problems creates a particularly challenging situation for children with ADHD. The researchers found that these behavioral factors were much stronger predictors than anything else they measured.

Interestingly, when the researchers looked at thinking and learning abilities using intelligence tests, they found no significant differences between the three groups. This was surprising because some people thought that cognitive problems might contribute to ODD development. Similarly, blood tests for vitamin D and thyroid hormones showed no meaningful differences between groups, suggesting these physical factors aren’t central to why some children with ADHD develop ODD.

Beyond the main findings, the study showed that emotional dysregulation (difficulty managing feelings) was notably worse in children with both ADHD and ODD. This suggests that the combination of ADHD and ODD creates a pattern where children struggle not just with attention and impulse control, but also with managing their emotions effectively. The study also confirmed that ADHD and ODD frequently occur together, which aligns with what doctors have observed in clinical practice.

This study adds to existing research by clarifying which factors matter most in the ADHD-ODD combination. Previous research suggested that cognitive problems, vitamin deficiencies, or thyroid issues might play a role, but this study found that behavioral factors are much more important. The findings support the growing consensus among researchers that behavioral interventions should be the primary focus for children with both conditions, rather than looking for underlying physical or cognitive causes.

This study has several important limitations to consider. First, it’s a snapshot study, so it can’t prove that conduct problems cause ODD—only that they’re connected. Second, the study relied entirely on parent reports of behavior, which can be influenced by a parent’s own stress or perspective. Third, the study only measured two blood markers (vitamin D and thyroid hormones), so other physical factors weren’t explored. Fourth, the study included children ages 6-12, so the findings may not apply to teenagers or adults. Finally, the study didn’t measure other factors that might be important, like family stress, trauma, or sleep problems.

The Bottom Line

Based on this research, behavioral interventions that specifically target conduct problems and impulsivity appear to be the most evidence-based approach for children with both ADHD and ODD. These might include parent training programs, behavioral therapy, or school-based interventions. There’s moderate confidence in these recommendations because the study clearly identified behavior as the key factor. However, this doesn’t mean other treatments aren’t helpful—medication for ADHD, for example, may still be important. Talk with your child’s doctor about a comprehensive treatment plan that addresses behavior as a priority.

Parents and caregivers of children with ADHD who notice defiant or conduct problems should pay special attention to these findings. Teachers and school counselors working with these children should also understand that behavioral strategies are likely to be most effective. Children with ADHD alone (without ODD) may benefit from different approaches. This research is less relevant for children without ADHD or for teenagers and adults, since the study only included children ages 6-12.

Behavioral changes typically don’t happen overnight. Most behavioral interventions require consistent effort for several weeks to months before meaningful improvements appear. Parents should expect to see small improvements within 4-6 weeks of starting a behavioral program, with more significant changes developing over 3-6 months. It’s important to be patient and consistent, as behavior change is a gradual process.

Want to Apply This Research?

  • Track specific conduct behaviors daily, such as number of times your child talks back, breaks rules, or shows aggression. Use a simple scale (0-5) to rate emotional outbursts and impulsivity each evening. This creates a baseline and helps you see if behavioral interventions are working over time.
  • Work with your child’s doctor or therapist to identify one specific conduct problem to target first (for example, talking back or aggression). Use the app to log when this behavior happens, what triggered it, and how you responded. This helps identify patterns and track progress as you implement behavioral strategies.
  • Set weekly check-ins to review your tracking data and look for trends. Compare week-to-week progress to see if the behavior is improving, staying the same, or getting worse. Share this data with your child’s healthcare provider to adjust treatment plans as needed. Track not just the problem behaviors, but also positive behaviors to celebrate progress.

This research provides insights into factors associated with oppositional defiant disorder in children with ADHD, but it does not establish cause-and-effect relationships. This study should not be used to diagnose or treat any condition. If you’re concerned that your child may have ADHD, ODD, or other behavioral or developmental issues, please consult with a qualified healthcare provider, pediatrician, or child psychologist for proper evaluation and personalized treatment recommendations. The findings presented here are based on a single cross-sectional study and should be considered alongside other available evidence and professional medical advice.