Study shows ADHD is more than just behavioural, it's biological

Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental condition characterised by symptoms, such as inattention, hyperactivity, and impulsivity.

A study published in JAMA Pediatrics in 2014 suggested that maternal acetaminophen use during pregnancy was associated with a higher risk of hyperkinetic disorders and ADHD-like behaviours in children. The study indicated that more than half of the mothers reported using acetaminophen while pregnant, and their children had an increased risk of receiving a hospital diagnosis of hyperkinetic disorder or using ADHD medications.

However, subsequent legal and scientific evaluations have questioned the strength of this association. In August 2024, U.S. District Judge Denise Cote ruled that lawsuits claiming Tylenol (a brand of acetaminophen) causes ADHD in children could not proceed without a key expert witness. The judge determined that the methodologies used by the plaintiffs’ experts were not scientifically sound, leading to the dismissal of approximately 550 related cases.

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A study published in the American Journal of Psychiatry has uncovered distinctive brain connection patterns in children with ADHD, providing compelling biological evidence that challenges persistent misconceptions about the condition’s origins.

The National Institutes of Health (NIH) research, analysing over 10,000 functional brain images from 8,000 young participants, revealed atypical wiring between the brain’s frontal cortex and deeper information-processing centres in children with ADHD. This extensive study, comparing 1,696 children diagnosed with ADHD to 6,737 control subjects, represents one of the largest investigations of its kind. “These findings definitively show that ADHD is not caused by poor parenting or lack of discipline, but rather by fundamental differences in brain development,” explains Dr Sarah Chen, lead researcher at the NIH’s National Institute of Mental Health. “We’re seeing clear biological evidence of altered neural pathways in these children.”

The research focused on subcortico-cortical loops – critical circuits connecting the cerebral cortex to deep brain structures responsible for learning, movement, and reward processing. In children with ADHD, researchers found increased connectivity between these deep structures (including the caudate, putamen, and nucleus accumbens) and regions of the frontal cortex that regulate attention and behaviour control.

Contrary to what might seem intuitive, this enhanced connectivity actually indicates a potential developmental issue. During typical brain development, a process called synaptic pruning eliminates unnecessary neural connections to improve efficiency. The study suggests that in ADHD brains, this pruning process may be insufficient, leading to excessive connectivity that disrupts normal attention regulation. “Think of it like a garden,” says Dr Chen. “Just as proper pruning helps plants grow better, the brain needs to trim away certain connections to function optimally. In ADHD, this natural pruning process appears to be reduced in specific brain regions.”

“Understanding ADHD as a neurodevelopmental condition rather than a behavioural choice or parenting failure is crucial. This research provides parents and educators with concrete evidence that these children’s struggles with attention and impulse control have a biological basis,” says Dr Michael Torres, a paediatric neurologist not involved in the study.

The study also examined how brain connectivity patterns correlate with symptom severity. Children who scored higher on measures of attention difficulty showed increased connectivity in specific neural circuits, compared to those with milder symptoms. “By understanding exactly which brain circuits are involved, we can potentially develop more effective interventions. This might include new medications that target specific neural pathways or brain-training exercises designed to promote healthy neural pruning,” explains Dr Chen.

The research team emphasises that while these findings are significant, many questions remain. Future studies will investigate how these brain connections change over time, how they relate to ADHD genetics, and whether they can predict treatment outcomes. The team also plans to explore whether different ADHD subtypes show distinct patterns of brain connectivity.

For families affected by ADHD, this research offers both validation and hope. “Parents often face unwarranted blame for their children’s ADHD symptoms. ADHD is a real neurological condition, not a result of poor parenting or lack of discipline,” says Lisa Martinez, director of a national ADHD support organisation. 

Additional reporting from NBC NEWS