Medication Not the Culprit in ADHD Brain Shrinkage
According to the National Institute of Mental Health, attention deficit hyperactivity disorder (ADHD) affects an estimated 1 out of every 25 youths between the ages of 9 and 17. Children who are not treated for their ADHD are at increased risk for antisocial behavior, drug abuse, and injuries. ADHD has also been shown to have long-term negative effects on academic performance, vocational success, and social-emotional development.
In the past, researchers have noted various brain abnormalities in people with ADHD, though it is not known whether this precedes or follows the condition. Many thought that medications used to treat the condition were the cause, but new research in the October 9, 2002 Journal of the American Medical Association (JAMA) reveals this is not the case. This study—the largest of its kind—was the first to follow children and adolescents over time and to look at ADHD children not taking medication.
About the Study
Researchers from the National Institute of Mental Health studied 291 children and adolescents between the ages of 5 and 18 over a 10-year period to gain insight into brain growth and development in people with ADHD. Study participants were recruited from local Bethesda, Maryland schools and volunteer programs.
Children with ADHD (89 males, 63 females) were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition . Specifically, the diagnosis was based on predetermined scores for hyperactivity, inattentiveness, and impulsive behaviors. Children without ADHD (83 males, 56 females) were screened through telephone interviews, parent and teacher rating scales, in-person assessments, including physical and neurological examinations, and clinical history obtained by a psychiatrist. Children without ADHD were matched to children with ADHD based on age and gender. All participants had an IQ greater than 80 and no evidence or history of a medical or neurological disorder, Tourette syndrome, or any other psychiatric disorder requiring drug treatment.
All participants were studied using the same MRI machine, and a computer was used to analyze the MRI images to calculate the brain volume. Each child was scanned 1 to 4 times over the study period, and the scans were visually inspected to exclude those with errors due to motion. A total of 544 brain scans (92%) were processed successfully and used for this analysis.
The brain volumes of children who had ADHD were compared with children who did not have ADHD. Researchers also compared the brain volumes of ADHD patients not taking medication for their ADHD with those of children who did not have ADHD.
Overall, brain volumes of children with ADHD were 3% to 4% smaller than brain volumes of those without the condition, though this size difference is too small to “diagnose” ADHD as some have hoped. This decreased brain volume was most pronounced in the unmedicated ADHD patients, leading researchers to speculate that the medication may actually be enhancing the brain development in children with ADHD. However, because the unmedicated ADHD patients were significantly younger than the medicated patients and controls, the size difference could be due to the fact that certain sections of the brain increase with age. In addition, it was discovered that ADHD children with the smallest brain volumes had the most severe symptoms of ADHD.
Even though the brain volume was significantly smaller, the brain development of those with ADHD paralleled that of those without the condition, suggesting that whatever caused the disorder happened earlier.
Adjustments made for vocabulary, medication status, height, weight, handedness (right or left), and gender had little effect on the outcome of the study.
Although these findings suggest that drug therapy for ADHD does not decrease brain volume, this study has its limitations. Because ADHD cases were referred to the study (not found in some other random way) and children without ADHD were carefully screened before enrollment, the children in this study might not adequately represent the population of US children. The study was originally designed to look only at males—2 to 3 times more boys get the condition—so the researchers recruited female cases that had ADHD severity similar to their sample of males. This may have led to enrollment of females who were, again, not representative of typical US females. Finally, significantly more scans from the children with ADHD could not be analyzed because of excessive movement during the MRI, though precautions like standardizing head placement were taken. This most likely removed the most symptomatic ADHD patients, meaning the differences in brain volume could have been even more striking.
How Does This Affect You?
Parents still need to carefully weigh the treatment options for their children with ADHD. There are clearly benefits and risks to medications, and behavioral therapies vary in their effectiveness. For instance, some studies suggest that drug therapy is more effective than behavioral therapies in controlling the inattention, hyperactivity/impulsiveness, and aggression seen in children with ADHD. However, it has also been noted that anxiety, academic performance, and social skills respond better to the combination of behavioral and drug therapies.
Although this study doesn’t provide new information about where in the brain things are going wrong for children with ADHD, the finding that ADHD medications are not causing the reduction in brain volume ought to be somewhat reassuring to parents with children taking these medications. More research using brain-imaging techniques (in addition to MRI) to follow neurologic changes in patients over long periods of time may offer insight into the causes, risk factors and best treatment options for this potentially serious condition.
American Academy of Child and Adolescent Psychiatry
National Institute of Mental Health
Castellanos FX, Lee PP, Sharp W, et al. Developmental trajectories of brain volume abnormalities in children and adolescents with attention-deficit/hyperactivity disorder. JAMA. 2002;288:1740-1748.
Castellanos FX, Giedd JN, Marsh WL, et al. Quantitative brain magnetic resonance imaging in attention-deficit hyperactivity disorder. Archives of General Psychiatry . 1996;53:607-616.
National Institutes of Health Consensus Development Conference Statement. Diagnosis and treatment of attention-deficit/hyperactivity disorder (ADHD). Journal of the American Academy of Child and Adolescent Psychiatry . 2000;39:182-193.
The MTA Cooperative Group. A 14-month randomized clinical trial of treatment strategies for attention-deficit/hyperactivity disorder. Multimodal treatment study of children with ADHD. Archives of General Psychiatry . 1999;56:1073-1086.
Last reviewed Oct 11, 2002 by ]]>Richard Glickman-Simon, MD]]>
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