New research reveals how adolescent ADHD and ODD ripple into adulthood—not through the symptoms themselves, but through disrupted education and mental health, with sharper consequences in contexts lacking strong social supports.
We often think of ADHD and oppositional defiant disorder (ODD) as “childhood conditions.”
Teachers report the disruptive behaviours, parents wrestle with exhaustion, and society assumes that these are phases that children will “grow out of.”
But the reality, as new research from Finland shows, is that the impact doesn’t disappear with adolescence.
It just changes shape.
What the Study Found
Researchers tracked young people from age 16 to 30. Here’s what they found:
No direct link: Having ADHD or ODD symptoms at 16 didn’t directly lower income at age 30.
But strong indirect effects:
Education: Teens with ADHD (especially when ODD was also present) were less likely to complete higher education, which sharply reduced their earning potential.
Mental health: Continued psychiatric struggles also explained income differences.
Having ADHD or ODD symptoms at 16 didn’t directly lower income at age 30. The impact flowed indirectly—through disrupted education and continued psychiatric struggles.
Males with ADHD/ODD fared the worst, earning nearly half the income of their peers by age 30.
Females with ADHD or ADHD/ODD also saw reduced earnings, though less extreme.
ODD alone was not a strong predictor of income loss—but when combined with ADHD, it amplified the risks significantly.
Social capital (trust, relationships, family life) didn’t explain the income gap—likely because Finland’s welfare state cushions some of those effects.
Why Context Matters
Now, here’s where we need to pause.
This study was done in Finland—a country with robust welfare systems, universal education access, and strong social safety nets. Despite that, the ripple effects of ADHD and ADHD/ODD still produced measurable economic gaps.
Imagine what this looks like in countries where the safety net is thinner.
In South Africa, where I live, school support for ADHD is inconsistent, often left to parents with means. ODD rarely enters the conversation at all—yet many children labelled as “problematic” may be navigating that very challenge.
Tertiary education is less accessible, and financial barriers create steep cliffs for those already struggling.
Mental health support is scarce, patchy, or prohibitively expensive.
In this context, the “indirect” effects found in Finland likely land much harder elsewhere. The income gap doesn’t just reflect fewer qualifications; it can mean unemployment, poverty, or cycles of marginalisation.
Rethinking ODD in the Equation
ODD is often dismissed as simple “defiance.” A child refuses to follow instructions, argues, or resists authority. Too often, this is labelled as bad behaviour rather than understood as a neurodevelopmental challenge.
But when ODD co-occurs with ADHD, it becomes more than just disruptive behaviour. It compounds the risks of underachievement, disengagement from school, and psychiatric difficulties later on. This study shows that while ODD alone doesn’t predict lower income, its presence with ADHD marks those most at risk.
In other words: ODD isn’t just noise—it’s an amplifier.
Why This Matters for Late-Diagnosed Adults
For many adults diagnosed late with ADHD (and sometimes recognising ODD traits only in hindsight), this research helps make sense of lived experience.
Struggles in education, fractured mental health, and inconsistent support systems often explain more about adult outcomes than the symptoms themselves.
If anything, it underlines the need for policies and programs that don’t just focus on children with neat diagnostic labels, but also on adults carrying the long shadow of unmet needs.
“The challenges of ADHD and ODD don’t simply vanish in adulthood. Instead, they transform into longer-term disadvantages—especially in education, mental health, and financial outcomes.”
The Bigger Takeaway
This research offers three urgent lessons:
Intervene early. Support for education and mental health in adolescence changes the trajectory of adulthood.
Don’t ignore ODD. When paired with ADHD, it signals compounding risks that demand attention.
Context shapes outcomes. A 47% income gap in Finland could easily become full-blown exclusion in South Africa, where systems of support are fragile or absent.
Ultimately, ADHD and ODD are not childhood conditions we grow out of—they are challenges we carry forward unless society builds the scaffolding to help us climb higher.
The study validates something many late-diagnosed adults already know—what limits our outcomes is not ADHD itself, but the systems that failed to support us at the right time.
