Like ADHD parent, like ADHD child?
We know, generally, that ADHD does run in families. Maybe you’ve heard about an adult who found out they had ADHD by taking their kid to get diagnosed, only to have the diagnosis turned on them!
The reason ADHD runs in families is that it has a large genetic component. Studies of twins with and without ADHD have estimated ADHD’s heritability at about 70-80 percent. In other words, it appears that about 70-80 percent of the variation in whether someone has ADHD comes down to their genes.
Still, that doesn’t answer another question: if a parent has ADHD, how likely is it that their child will also have ADHD?
A recent meta-analysis led by researchers at Massachusetts General Hospital and Harvard Medical School sheds some light on that question.
The meta-analysis, or “study of studies,” considered previously published studies of “high-risk children” – children whose parents had ADHD, putting the children at greater chance of having ADHD themselves.
As it turned out, those studies turned up a range of different findings on how prevalent ADHD was among high-risk children. The lowest estimate was that 9 percent of children from parents with ADHD had ADHD themselves while the highest estimate was 57 percent. However, even for the study with the lowest estimate, the 9 percent rate of ADHD was much higher than the rate among children whose parents didn’t have ADHD, which was 2 percent.
Averaging the data across studies, the authors of the meta-analysis found that 40 percent of children whose parents had ADHD also had ADHD themselves.
The researchers caution that just because 40 percent of the children have clinically diagnosable levels of ADHD symptoms doesn’t mean the other 60 percent resemble children whose parents don’t have ADHD.
In fact, previous research has suggested that children of parents with ADHD might have more subsyndromal ADHD symptoms, or ADHD symptoms that aren’t severe enough to be diagnosed. Therefore, the 60 percent of high-risk children without ADHD could still have low-level ADHD-like symptoms, and they could also have elevated risk for other psychiatric conditions.
As far as children of ADHDers who do go on to be diagnosed with ADHD, the 40 percent figure isn’t definitive. It’s an estimate based on the studies that have been done so far.
But it does confirm, pretty clearly, what we knew to expect based on the fact genes influence ADHD symptoms: when parents have ADHD, their children are much more likely to have ADHD as well.