New findings by National Human Genome Institute (NHGRI) researchers have provided insight into why some patients recover from childhood attention deficit hyperactivity disorder (ADHD), while others have symptoms that persist into adulthood. The study was published in The Proceedings of the National Academy of Science.
The team found that adults with persistent symptoms of ADHD had partially lost the typical balance of connections between brain networks responsible for daydreaming or introspection and networks that control action. This imbalance is thought to be responsible for the hallmark lapses of attention in ADHD. However, adults who had “outgrown” ADHD showed balanced brain activity.
In approximately 20% to 30% of people with ADHD, the full syndrome persists as young adults, while about 50% have partial remission.
"We hope to understand the mechanisms that explain why some people outgrow ADHD and others do not," said Philip Shaw, BMBCh, PhD, senior author of the study and an investigator in NHGRI's Social and Behavioral Research Branch. "If we can understand why some people can recover from ADHD, we also might be able to apply this knowledge to other neuro-developmental conditions like learning disabilities or problems with social interaction."
Investigators analyzed brain function in 205 adult participants—101 received a diagnosis of ADHD in childhood, and 104 had not had ADHD.
Changes in the brain's oxygen levels allowed functional MRI to isolate the location of brain networks. The different levels of neuronal activity were examined by looking at the brain's magnetic fields using magnetoencephalography.
Results showed that adults who had persistent inattentive symptoms from childhood lost the usual balance of connections between the “online” and “offline” brain networks, regardless of the type of brain imaging used. The loss was noted particularly in a network that is prominent in an introspective state, but that is switched off when a person is engaged in tasks.
This balance was partially lost in the adults with persistent inattention. In contrast, these connections were similar in patients who outgrew ADHD and in those who had never had ADHD. This result supports the theory that a childhood disruption to brain function corrects itself by adulthood among individuals who recover from ADHD.
"Most adults have a balance between the online, task-oriented brain and the offline, day-dreaming brain, but we found that's not the case for adults whose ADHD persists," said Gustavo Sudre, PhD, study co-author and postdoctoral research fellow in Dr. Shaw's lab. "We found that adults who recovered from ADHD had a very similar balance of online and offline brains to those who never had ADHD."
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