ADHD Kids Have Smaller Brains

But Medications Don't Affect Brain Size

From the WebMD Archives

Oct. 8, 2002 -- A new study confirms previous research showing that children with attention deficit hyperactivity disorder (ADHD) have smaller brains than children without the condition. And the study results may put some fears to rest regarding treating young children with medication.

Some parents have voiced concerns that using medication for ADHD in children could harm their brains. But experts say this study takes one step toward reassuring parents that medications, such as Ritalin, do not appear to have a harmful affect on brain size.

In fact, in children with ADHD who did not take medication, one area of the brain was actually smaller. The study is reported in the Oct. 9 issue of The Journal of the American Medical Association.

Researchers report that ADHD children not on medication tested the lowest on some brain size measures as determined by MRI scan. The inner "white matter" area of their brains, which mostly consists of nerve cells and plays a key role in motor coordination, measured 9% smaller compared with ADHD children on medication and 11% smaller than the brains of children without the condition.

The overall brain size was found to be 3% smaller in ADHD children, according to the 10-year study. Specific regions of the brain were also tested and consistently measured smaller in ADHD children. However, there was no distinguishable difference in size or growth patterns in most brain areas between ADHD children who took medication and those who did not. But brain sizes and growth did tend to consistently lag behind children without ADHD.

This study backs earlier findings, including one by the same research team that produced similar results.

"The message for parents is this: What we found is a brain difference in those with ADHD -- not a brain defect," study researcher Jay Giedd, MD, chief of brain imaging at the NIH's Child Psychiatry Branch, tells WebMD. "We never found any damage to the brain in those with ADHD, no foul play or damage or funny business of any kind."

Over a decade, researchers performed multiple MRI brain scans on each of the 152 ADHD and 130 comparison participants, all between 5 and 19 years old. They assessed how ADHD -- and the medications taken for it -- affect brain size and long-term growth.

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ADHD, which affects about 5% of school-aged children -- at least 2 million Americans -- is usually treated with stimulant medications such as Ritalin and Adderall. These drugs offer almost immediate and dramatic improvement in about 80% of patients, says the American Psychiatric Association. Along with medication, special education and psychotherapy are also recommended.

"Our findings should not be interpreted as a blanket endorsement for the use of medications to treat ADHD, but it certainly shouldn't deter it, either," Giedd tells WebMD. "Not only did ADHD people who don't get the medicine have these brain differences, but in some ways they were even more pronounced. As a parent, you also hear about the risks of using medication to treat a condition. Now with ADHD, there is the risk of not using it."

Children with ADHD often have trouble paying attention or maintaining interest, get distracted easily, and demonstrate hyperactive and impulsive behaviors such as frequent fidgeting, blurting out, or having difficulty while waiting in line.

Some experts believe the study could be useful in putting an ADHD diagnosis into perspective, especially for parents.

"The value of this study is that it lends value to the credibility that ADHD is an organic condition -- and not the result of bad parenting or a child simply behaving badly," says ADHD specialist Janice Woolley, MD, pediatrician at the Pugent Sound Behavioral Medicine Clinic in Mercer Island, Wash. "It's also useful because rarely is medication a parent's first choice for treatment. Many parents I see have tried other interventions. But a study like this is helpful in adding to our body of understanding that ADHD medication has a good record for long-term safety. We all want to be sure that we don't look back in a few years and see unexpected consequences that result from medication."

Although its exact cause is unknown, ADHD could result from a genetic predisposition or complications in the womb or during delivery. The disorder usually is diagnosed between ages 8 and 10, although it can occur earlier. Statistics indicate that it is three times as common in boys than girls, but a recent study suggests the disorder is often overlooked in girls because they may have a less disruptive type.

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About 30% of children "outgrow" the hyperactivity aspect of the disorder, but without proper treatment, problems with attention and concentration often continue throughout life.

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