New Insights Show How ADHD Is Likely Passed On From Parents To Children

It’s no secret that parents can often pass down certain physical traits to their children. A kid has her mom’s eyes and her dad’s smile. Hair color, eye color, and other physical traits often get passed down generation after generation.

Scientists now know that this type of generational inheritance of physical traits also applies for neurodevelopment and mental health. Children of a parent with a neurodevelopmental condition have an increased risk of developing the same or a related condition.

Now, researchers have found new insights into how this risk transmission of neurodevelopmental conditions (specifically attention-deficit hyperactivity disorder (ADHD)) occurs from parent to child.

In a new study published in Molecular Psychiatry, researchers looked at risk transmission across generations for traits characteristic of ADHD and boiled it down to two possible causes — genetic transmission and environmental circumstances.

Scientists wanted to see if nature, nurture, or a bit of both could be the culprit for why kids are at a higher risk for inheriting ADHD if their parents also have the neurodevelopmental disorder.

Genetic transmission of ADHD genes happen when ADHD traits are found in both parents and their child. The study reminds parents that even if the child is not reared by their biological parents, the risk will still be there.

Researchers also made the case for environmental reasons. A parent who has ADHD might have certain behaviors and structure their home in a way that may in turn contribute to increased ADHD traits in children.

The new study examined the role of genetics in the development of ADHD traits in 19,500 children and their parents by having them genotyped. Genotyping is the process of determining differences in the genetic make-up of an individual by examining the individual's DNA sequence.

By genotyping these families, researchers were able to calculate polygenic scores — an index of a person’s genetic tendency to a specific trait or disorder — for both parents and their children. The study also measured children’s ADHD traits by having their mothers rate their child’s behavior.

Using these polygenic scores, researchers were able to dissect associations between children’s ADHD traits and parent’s polygenic scores into two components: nature vs. nurture.

“The results indicated that most parental characteristics, including parents’ ADHD, smoking, education levels, and cognitive abilities, are linked to their children’s ADHD traits, at least in part, due to genetic transmission,” lead researchers Wikus Barkhuizen, Ph.D. and Jean-Baptiste Pingault, Ph.D. wrote for Psychology Today.

“We found little evidence that parental characteristics influence children’s ADHD traits because of genetic nurture. One exception was that mother’s polygenic score for neuroticism was associated with children’s ADHD traits after controlling for genetic transmission, indicating genetic nurture effects.”

The new findings indicated that the transmission of ADHD traits from one generation to the next is largely explained by the genetic makeup of parents passed down to their children, rather than environmental reasons.

As a result, previous evidence for associations between parents’ characteristics and their children’s ADHD traits may have overestimated the importance of environmental effects. It seems that it;s much more left up to fate and the “genetic lottery that makes each child unique.”

These new findings should give neurodivergent parents a sigh of relief and hopefully relieve some of that guilt they may feel for having their ADHD “passed down” to their kids. This new study finds that it is a lot less likely that the way you organize (or don’t organize) your house or any other type of “non-typical” behavior you may exhibit as a parent is the reason why your child also has ADHD.

That being said, researchers, Barkhuizen and Pingault, also want to emphasize that parenting matters when it comes to a child with a neurodevleopment disorder.

“There is evidence, for instance, that parent coaching support can improve functioning in children with ADHD. Environmental influences can make a difference in the outcomes of children, even when aspects of their development are genetically influenced,” they wrote.

Read the entire study breakdown here.