connected neuronsAround 11% of children have attention deficit hyperactivity disorder (ADHD). Many of those children become adults with ADHD, but just as many adults “outgrow” the disorder. Why does ADHD persist for some, but not others? A study from MIT is the first to research how the brain’s communication network affects ADHD in adults and why some adults recover from ADHD. The findings indicate that there is a biological basis for adult ADHD.

The researchers evaluated 35 adults. All the adults were diagnosed with ADHD as children, but only 13 still had ADHD at the time of the study. Using a resting-state functional MRI (fMRI), the researchers observed which parts of the brain were active when the subjects were awake, but resting. Most fMRI studies require that participants do something as they are scanned, but for this study, the participants did not complete any tasks. This allowed the researchers to see the brain’s overarching patterns unaffected by patterns required to perform certain activities.

One of the brain’s major communication networks, called the default mode network, is a key factor in whether an adult recovers from ADHD. The default mode network consists of two hubs: the posterior cingulate cortex and the medial prefrontal cortex. For people without ADHD, the two hubs’ activity is synchronized, but people without ADHD have unsynchronized hubs. The study demonstrated that the default mode network became synchronized in adults who outgrew ADHD. Brains of adults who outgrew ADHD resemble those of people who never had ADHD.

The researchers also found some similarities between the two groups of adults studied in the brain’s task positive network. The task positive network works with the default mode network to support executive functioning. For people without ADHD, either the task positive network or the default mode network is active—one suppresses the other. However, adults with ADHD and adults who outgrew ADHD had both networks active simultaneously, which hinders the ability to focus.

“The psychiatric guidelines for whether a person’s ADHD is persistent or remitted are based on lots of clinical studies and impressions. This new study suggests that there is a real biological boundary between those two sets of patients,” stated John Gabrieli, one of the study’s authors and professor of brain and cognitive sciences at MIT.

This research is published in the journal Brain.

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