The differences in the brains of people with ADHD have been hard to pin down, often because imaging studies keep contradicting each other. One study would find more gray matter in one region, another one would find less, and that leaves researchers with no clear idea of what’s going on with the brains of those with ADHD.
A new study published in General Psychiatry suggests the real issue might be a lot less complicated than we thought. The researchers suggest that there are actually three different types of ADHD, and that past research teams have been lumping them together as if they were one.
Using MRI scans from the ADHD-200 dataset, researchers in China analyzed brain images from 135 children with ADHD and 182 neurotypical peers. Instead of treating ADHD as one group, they used a machine-learning system called HYDRA to sort participants by patterns in gray matter.
They found distinct neurological subgroups, and each couldn’t be more different than the next. The three types of ADHD they found were described as:
- severe combined with emotional dysregulation
- predominantly hyperactive/impulsive
- predominantly inattentive
Your Brain Looks Different Depending on the Type of ADHD You Have
The first group showed increased gray matter across large areas of the brain compared with neurotypical children. Differences were mostly concentrated in the frontal lobes, which regulate attention and impulse control. They were also in the cerebellum, a region linked to attention processing. Kids in this group tended to show symptoms most strongly associated with inattentiveness.
The second group showed the opposite: reduced gray matter in several regions, particularly the cerebellum and the hippocampus, which plays a role in memory, motivation, and emotional regulation. This subtype showed the broader set of symptoms we tend to associate with ADHD, like hyperactivity, impulsivity, and inattention. One weird observation was that the early stages of this group showed almost no detectable brain differences. It wasn’t until the symptoms became more severe that the structural changes became noticeable.
This study also helps explain why ADHD brain studies have been wildly inconsistent. When researchers analyze all 135 children with ADHD together, no significant brain differences appear at all. The opposing patterns basically cancel each other out.
One big benefit of this research is that it could help us better diagnose ADHD. It’s currently diagnosed almost entirely through behavioral observation. This research suggests that a single diagnosis may not be refined enough to understand the different neurological pathways at play. And with different pathways at play, that means three kids with the same diagnosis can respond very differently to the same therapy. In the future, that may not be the case anymore.
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