Attention deficit hyperactivity disorder, or ADHD, was once considered a problem that children outgrew. If they didn’t, their parents were often blamed for bad parenting. But researchers have found that ADHD is a very real disorder rooted in brain development. Effective treatments are now available, and researchers continue to make progress in understanding what causes ADHD—as well as how to prevent and treat it.
Many people blurt out things they didn’t mean to say from time to time, or jump from one task to another, or become disorganized and forgetful. But people with ADHD have more serious problems that get in the way of their school, work and family life. They have trouble staying focused and paying attention, difficulty controlling behavior, and very high levels of activity.
“The key to a diagnosis of ADHD is that the symptoms are impairing for the child,” says Dr. Philip Shaw in the Child Psychiatry Branch at NIH’s National Institute of Mental Health (NIMH). “Kids with ADHD often really struggle at school, and the symptoms can impair the child’s family life and relationships with peers.”
“The great majority of cases start by age 7,” says Dr. Judith Rapoport, chief of the NIMH Child Psychiatry Branch. Adults can also be diagnosed with ADHD, but Rapoport says it’s difficult to tell whether the problems really started in adulthood. They may have had undiagnosed symptoms as children.
The causes of ADHD aren’t fully understood, but genes play a role. “ADHD is one of the most heritable of all childhood mental health problems,” Shaw says. “About 70-80% is caused by heritable genetic factors.”
But it’s been difficult to pinpoint which genes are involved. “Like most psychiatric disorders,” Rapoport says, “it looks like there’s a number of genes with a very small effect.” At least 20 genes have been linked to ADHD, she says. Most of the genetic variations are found in the general population, but they’re a little more common in people with ADHD.
Environmental factors also play a role. “Like nearly all childhood mental health problems,” Shaw says, “ADHD is a complex mix of genetic factors and environmental factors and their interaction.”
Mothers who smoke or drink excessive amounts of alcohol during pregnancy are more likely to have children with ADHD. Lead exposure has been very strongly associated with ADHD symptoms. And some evidence suggests that certain food additives may have a small effect.
Brain imaging studies have shed some light on how ADHD unfolds. Development in some regions of the brain is delayed by an average of 3 years—and up to 6—in kids with ADHD. This delay is most marked in an area involved in focusing attention, working for reward and planning, among other things. In most kids, this part of the brain—the frontal cortex—is fully developed by the age of 7 or 8. For kids with ADHD, it’s between 10 and 13.
“That delay is carried forward into adolescence,” Shaw says. “We know that changes in brain structure and function can often persist into teenage years and beyond in people who have ADHD.”
Research has yielded insight into the brain chemistry of ADHD as well. One of the main brain chemicals that seems to be disrupted is dopamine. The chief class of medications used to treat ADHD, called psychostimulants, apparently act by boosting the levels of dopamine in the brain. Other brain chemicals have also been tied to ADHD, and new medications to target them are becoming available. What these chemicals have in common is that brain cells use them to communicate with each other.
Medication can control symptoms in moderate to severe cases of ADHD, Rapoport says. Behavioral treatment, or psychotherapy, is also sometimes used. A large NIMH-funded study found that combining behavioral treatment with medication is more effective than either treatment alone. Families and teachers reported being more satisfied when treatments included behavioral therapy.
“The kids that benefit most from behavioral treatment tend to be those who have ADHD complicated by other mental health problems,” Shaw says.
Mental health professionals, Rapoport explains, can make a big difference by helping parents to become less critical and frustrated. “Children do better when they have parents that aren’t judgmental,” she says. “Counseling and education sessions are important for the family so they understand what can be helpful and also what the school can do.”
Schools can play a major role in helping a child with ADHD. Rapoport says, “Having the child sit in the first row can be very helpful for mild cases.” Teachers can lend a hand by pointing out when a child isn’t paying attention. Sometimes a little bit of gentle guidance can help children correct themselves.
For some kids, ADHD symptoms fade as they grow up, but others may face continuing problems. A recent study found that adults with ADHD have higher than average rates of divorce, unemployment, substance abuse and disability. Although many adults with ADHD receive treatment for other mental disorders or substance abuse, fewer receive treatment for their ADHD symptoms.
Researchers are now using brain imaging to compare the brains of adults who recover from ADHD with those who never grew out of it. “We’re trying to understand why ADHD has such a variable outcome,” Shaw says. “If you take 100 children with ADHD and look at how they’re doing when they’re adults, some are completely better, some are essentially unchanged and a large chunk are somewhere in the middle. We’re looking at the brain basis for that variable outcome.”
Scientists also continue to seek the root causes of ADHD. They’re looking into many other aspects of ADHD as well, like how treatments in childhood affect long-term outcomes. Other researchers are trying to relate genetic differences to how the brain develops in ADHD. The ultimate goal, of course, is to find better ways to diagnose and treat the disorder.
But effective treatments are already available for ADHD. See your doctor if you suspect your child may have a problem.