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Does genetics play a role in ADHD and can ADHD be inherited? There are now several dozen case studies showing that ADHD does run in families.

When a child is diagnosed with ADHD, it often pays to look at the adults in the family, too. ADHD sometimes runs in families, and parents or grandparents may also have it.

When Michele Novotni was pregnant with her son, Jarryd, she might have guessed that he would become a child with attention deficit hyperactivity disorder (ADHD). After all, while in the womb, he was so active. Before he was 2 years old, he was diagnosed with ADHD, and he began taking medication for the disorder at age 5.

As Jarryd's family began dealing with the challenges of his ADHD, Novotni contemplated whether her father might also be afflicted with the same disorder, even though it had never been diagnosed. "We didn't know why my father had never worked up to his potential," says Novotni, PhD, a clinical psychologist in Wayne, Pa.

Before long, Novotni's father was, in fact, diagnosed with ADHD at the age of 65. He has been treated with a combination of strategies, including medication and personal coaching, and "it has made a huge difference in his life," she says.

Among Novotni's relatives, the family tree of ADHD doesn't stop there. One of her sisters has ADHD. So do several of her nephews.

ADHD Running in Families

ADHD can be inherited. Read how doctors and therapists are encountering families with multiple ADHD cases.The familial nature of ADHD isn't uncommon. With increasing frequency, child and adult psychologists and psychiatrists are encountering families with multiple ADHD cases. More than 20 studies now confirm that the tendency to develop ADHD can be inherited, often affecting not only parents and their children, but also cousins, uncles, and aunts in the same extended family.

For example, when one child in a family has ADHD, a sibling will also have the disorder 20% to 25% of the time, says geneticist Susan Smalley, PhD, co-director of the Center for Neurobehavioral Genetics at the David Geffen School of Medicine at UCLA ( About 15% to 40% of children with ADHD will have at least one parent with the same condition.

The prevalence of ADHD within families is particularly striking in studies of twins. Identical twins share all of their genes, and when one sibling has the disorder, his or her twin will have the condition 70% to 80% of the time. With non-identical or fraternal twins, ADHD occurs in both siblings in 30% to 40% of cases.

The Parent-Child Connection

ADHD is the most common behavioral disorder diagnosed in children, and overall it affects up to 7.5% of school-age youngsters, according to a recent Mayo Clinic report. But though ADHD is often perceived as a childhood condition, it also occurs in about 2% to 6% of adults. Although by definition ADHD is a disorder that always begins in childhood, many adults with the condition may never have been diagnosed while growing up.

"Often, when we do assessments of children, a parent will say, 'That sounds a lot like me,'" says Novotni, author of Adult ADHD: A Reader Friendly Guide and president of the Attention Deficit Disorder Association ( "Or the parent might say, 'So that's why it took me three times longer than other students to study for tests.'"

But while genetics clearly have an important role in ADHD, it is not the only influence. Environmental factors are players in the equation as well, such as smoking or alcohol use by a mother during pregnancy, and extremely low birth weight of the newborn, which could delay the development of the baby's brain and put him at risk for ADHD. Toxins in the environment and dietary factors might also be pieces of the puzzle in some cases, but they need to be better studied.

According to Smalley, ADHD is the result of a blending of factors. "ADHD is always caused by a combination of a genetic predisposition to get ADHD, and then the kind of environmental factors that interact with that genetic predisposition."

Family Challenges

Families with multiple members with ADHD face special challenges in coping with the condition. A parent with ADHD may find it challenging to maintain self-control while dealing with a difficult child because of the parent's own emotional difficulties, says Arthur Robin, PhD, professor of psychiatry and behavioral neurosciences at Wayne State University School of Medicine in Detroit. "Parents may have a harder time inhibiting their own emotions and thinking things through before they act," he says. "The child's rashness and impulsiveness may evoke a reaction from the parent, creating an escalating and explosive situation."

Though hyperactive behavior and impulsivity are common characteristics in children with ADHD, the symptoms often change as these youngsters grow into adults. A study at Massachusetts General Hospital concluded that adults with the condition often are restless, easily distracted, have difficulty following directions, and frequently lose items -- but may not be hyperactive or impulsive like their own ADHD children.