ADHD is partially genetic, but there are other risk factors that play a key role
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ADHD is partially genetic, but that is not the only factor.
One study estimated that there is an 88% chance that ADHD can be passed down in families.
Other risk factors that can contribute to ADHD are premature birth, childhood exposure to lead, and childhood trauma or adversity.
This article was medically reviewed by Zlatin Ivanov, MD, who is certified in psychiatry and addiction psychiatry by the American Board of Psychiatry and Neurology at Psychiatrist NYC.
Some mental health conditions have genetic components, and the same can be said for attention deficit hyperactivity disorder (ADHD).
Research have some insight into the genetic component of the condition. However, there are more to potential causes of ADHD aside from just your genes.
Here's what scientists know so far about the heritability of ADHD and how it compares to other risks that contribute to the condition.
ADHD can be passed down in families
Though it's unclear how significant a role genetics plays, studies have shown that having a parent or sibling can drastically increase one's risk of developing ADHD.
For example, a 2016 study published in Neuropsychiatric Disease and Treatment found that in the sample of 79 children with ADHD, 41.3% had mothers with ADHD and 51% had fathers with ADHD.
Another study, published in 2017 in Revista Colombiana de Psiquiatría, found that siblings of someone with ADHD had a 26% to 45.2% chance of also having ADHD — making it a greater likelihood than if no siblings had ADHD.
Another 2014 study of 59,514 twins found the heritability of ADHD — the likelihood of a genetic component for the condition — to be 88%. However, genetics are likely not the sole factor for whether or not a person develops ADHD.
"Since siblings also share a social, physical, and rearing environment, this in itself does not prove genetic rather than potentially shared environmental causes," says Robert King, MD,
Pediatric Developmental and Behavioral Medicine Psychiatrist and Medical Director of the Tourette's/OCD Clinic at Yale Child Study Center.
Is there a specific gene that has been linked to ADHD?
There is no one gene that causes ADHD, and there is no test you can take to determine your risk of developing it. In fact, ADHD is most likely a condition associated with multiple genes, not just one, says King.
But researchers have hypothesized that one gene in particular, the DRD4 gene, may play a part in ADHD. The DRD4 gene affects dopamine receptors in the brain, which in turn can influence brain function and mental disorders associated with brian function, including ADHD. However, how strong a role DRD4 plays in ADHD, specifically, remains unclear.
King says that researchers have found other rare genes that are associated with different aspects of brain development, but clarifies that "although these are of interest in suggesting new research leads, they are found only in a very small number of cases of ADHD and are not useful as any sort of diagnostic test."
Another factor that makes genetic studies for ADHD so complicated is the fact that ADHD is often co-occurring with other mental health conditions like anxiety, depression, and tic disorders, King says, and these disorders may also be partly genetic.
Other risk factors for ADHD
King says that aside from genetics, various other factors predispose somebody to ADHD, and some of them are preventable. Some examples of ADHD risk factors are:
Smoking during pregnancy: A 2018 meta-analysis of almost 3,000,000 participants published in Pediatrics found that children whose mothers smoked during pregnancy were more likely to have ADHD, and that risk increased the more a mother smoked — meaning that heavy smokers were more likely to have a child with ADHD. Alcohol and drug use during pregnancy can also contribute to risk, according to the National Institute of Mental Health.
Premature birth and low birth weight: Research has shown that both of these factors contribute to developing ADHD later in life. A 2017 meta-analysis published in Pediatrics looked at 1,787 subjects and determined that there was a significant correlation between preterm birth and extremely low birth weight and ADHD.
Childhood exposure to lead: If a child was exposed to lead, such as from household paint or leaded gasoline exhaust, King says this is a potent risk factor. A 2016 systematic review published in the Iranian Journal of Psychiatry examined 18 studies. In 16 out of the 18 studies, there was a strong link between ADHD and blood lead levels.
Childhood trauma or adversity: King says that non-genetic family aspects such as low family socioeconomic status or domestic violence can increase the risk of childhood ADHD.
The bottom line
While genetics are not the only factor in whether or not someone develops ADHD, there certainly is a genetic component, which has been proven through years of scientific research. However, there is not one specific gene that is directly associated with ADHD.
There are multiple non-genetic risk factors that may contribute to an individual's ADHD, as well. Regardless of what caused somebody's ADHD, there are multiple treatment options available that can help manage ADHD symptoms and improve quality of life.
Related articles from Health Reference:
The 3 types of non-stimulant ADHD medications and how they work
How to recognize the 3 different types of ADHD and treat them
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