What the Science Actually Says About ADHD Origins

ADHD is primarily genetic.
In fact, heritability estimates are around 70–80%,
meaning the vast majority of ADHD traits are inherited, not caused by the environment later in life.

Core findings:

• If a parent has ADHD, their child has a significantly higher chance of having it.

• Twin studies (identical vs. fraternal) show very high concordance rates for ADHD, pointing strongly to genetics.

• Multiple genes have been linked to ADHD traits, particularly those involved in dopamine regulation (like the DRD4 gene).

Environmental influences?

• Yes, but they are secondary — they influence severity, coping, and sometimes the timing of symptom presentation, not the core cause.

• Examples of environmental factors that can worsen or amplify ADHD symptoms:

  • Prenatal exposure to alcohol, tobacco, or drugs.

  • Premature birth or very low birth weight.

  • Severe early neglect or trauma (which can mimic ADHD symptoms, but is different at the neurological level).

  • Extreme lead exposure or neurotoxic exposure (very rare today).

  • Possibly very early immunological stress or inflammation (still being researched, not definitive).

What doesn’t cause ADHD?

• Parenting styles

• School environments

• Screen time

• Diet (although poor diet can exacerbate symptoms)

• Vaccinations (not linked to ADHD in any reputable study)