Biological Basis for Adult ADHD Revealed

Megan Brooks

June 20, 2014

Brain activity patterns differ in adults with persistent and remitted childhood attention-deficit/hyperactivity disorder (ADHD), new research shows.

In the first study to compare patterns of brain activity in adults who recovered from childhood ADHD with those who did not, neuroscientists at the Massachusetts Institute of Technology (MIT) in Cambridge have discovered key differences in a brain communication network that is active when the brain is at wakeful rest and is not focused on a particular task. The findings offer evidence of a biological basis for adult ADHD and could help to validate the criteria used to diagnose the disorder.

"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 2 sets of patients," study investigator John Gabrieli, PhD, MIT professor of brain and cognitive sciences, who worked on the study, said in a statement.

The study was published online June 10 in Brain.

Neurobiological Differences

Some children outgrow ADHD, whereas others continue to have attention problems in adulthood. It is estimated that 4% of the US adult population, or 8 million adults, have ADHD.

The goal of the MIT study was to see whether there are neurobiological differences in the brain between patients with persistent ADHD and those with remitted ADHD. The study included 35 adults who were diagnosed with ADHD as children (13 of whom continue to have ADHD, and 22 of whom have remitted ADHD) and 17 adults who never had ADHD, who served as controls.

"This sample really gave us a unique opportunity to ask questions about whether or not the brain basis of ADHD is similar in the remitted-ADHD and persistent-ADHD cohorts," Aaron Mattfeld, PhD, a postdoctoral associate at MIT's McGovern Institute for Brain Research, who is the lead author of the article, said in a statement.

Using resting-state functional MRI, the researchers found differences in activity patterns in the default mode network (DMN) in these 2 groups. Adults with remitted ADHD (and control participants) did not show the typical dysfunction in the DMN that is seen in children and adults with active ADHD. "Their brains now look like those of people who never had ADHD," Dr. Mattfeld said.

The researchers found more similarity in persistent and remitted ADHD patients in the task positive network (TPN), also known as the dorsal attention network.

When the DMN is active, the TPN is suppressed. When the brain is focused on a specific task, the TPN takes over and suppresses the DMN. If this reciprocal relationship degrades, the ability to focus declines.

The MIT study shows that both persistent and remitted ADHD patients have simultaneous activation of both networks, which may be a sign of impairment in executive function that is common in ADHD. In fact, both groups of ADHD patients performed poorly on tests of executive function.

This suggests that "once you have executive function problems, they seem to hang in there," Dr. Gabrieli said.

The research was supported by the Poitras Center for Affective Disorders Research at the McGovern Institute for Brain Research at MIT. Additional support was provided by the Pediatric Psychopharmacology Council Fund at Massachusetts General Hospital. A list of author disclosures is available online.

Brain. Published online June 10, 2014. Abstract


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