Despite extensive efforts, the cause of hyperactivity, the symptoms of which include motor restlessness, attention difficulties, distractibility and impulsiveness, remains unknown. Researchers have been unable to find consistent neurobiological differences between hyperactive and normal children. For this reason, the validity of hyperactivity (recently named Attention Deficit-Hyperactivity Disorder) as a physiological disorder has remained controversial as has widespread use of the stimulant medication used to treat it. Currently, two to four percent of school age children are identified as hyperactive.
The most recent research into hyperactivity, however, may represent a breakthrough. This past November, the New England Journal of Medicine published a report linking hyperactivity to significantly reduced levels of glucose metabolism in the brain. Since the brain scan used to measure glucose metabolism involved radioactive tracers, only adults were included in this research (symptoms persist in 40-60% of adults who were hyperactive as children). The study, headed by Alan J. Zametkin at the National Institute of Health, matched a group of normal adults with a group of hyperactive adults for age, I.Q., achievement level, education and socioeconomic status. Hyperactive adults who have a clear history of hyperactivity, no history of substance abuse, and who have a child identified as hyperactive (approximately 29% of parents with hyperactivity have a child who is hyperactive) were chosen to participate in this study. All hyperactive participants demonstrated continued attention difficulties, as well as restlessness. Approximately 25% of those participating in this study also exhibited learning disabilities.
Zametkin et al. found that the global glucose metabolism level was significantly lower in the brains of adults with hyperactivity. (No significant differences in glucose metabolism were found between the hyperactive patients who had learning disabilities and those who did not.) Importantly, the glucose level was lowest in those two specific areas of the brain which are involved in the control of attention and motor activity. Although this study involved only adults, hyperactive children commonly exhibit behaviors (calling out, interrupting and acting before thinking) which indicate problems in these same areas of the brain. This research, then, would indicate that at least some hyperactivity is due to a neurological disorder and is not a manifestation of emotional problems, lack of discipline or poor parenting.
“Cerebral Glucose Metabolism in Adults With Hyperactivity of Childhood Onset” The New England Journal of Medicine November 15, 1990, Volume 323, Number 20, p. 1362-1366.
Published in ERN January/February 1991 Volume 4 Number 1