ADHD: Large imaging study confirms differences in several brain regions

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Of seven subcortical brain regions targeted in the study, five, including the amygdala, were found to be smaller in those with ADHD, compared with those in a control group.

In conducting the largest brain imaging study of its kind, an worldwide team of researchers found that ADHD involves decreased volume in key brain regions, in particular the amygdala, which is responsible for regulating the emotions.

The researchers concluded that a delay in brain development is typical of the condition, hoping the analysis would stop people associating it with "difficult children" or bad parenting.

Outside scientists say the findings are interesting, but there wasn't enough information to link the brain differences to behavioral problems seen in people with ADHD.

The differences observed in their study were most prominent in children, but also present in adults with the condition.

Hoogman said the findings support previous theories that the brains of people with ADHD may develop more slowly but that those differences are mostly wiped out by the time children grow up.

The study, the largest to date of the brains of those with ADHD, was conducted by The Lancet: Psychiatry.

But the differences are also really hard to spot, according to Hoogman, who says the brains of one group only differed by "a few percent - so the unprecedented size of our study was crucial to help identify these".

For the new study, Dr. Hoogman and colleagues measured differences in brain structure from MRI scans of 1,713 participants diagnosed with ADHD, and in 1,529 other people (the controls) who did not have ADHD. The researchers also looked at the effect of age, gender, medication and other psychiatric disorders.

The affected regions include the amygdala, which is involved in the regulation of emotion.

The differences between the two types of brain are not monumental however, according to the study's lead author, Martine Hoogman.

Another recent study in ADHD dates back to May past year, and posits that children with the disorder have some symptoms also found with rare forms of cancer.

The study also took into account people who had taken medication to treat ADHD, such as methylphenidate, more commonly known as Ritalin.

Dr. Jonathan Posner, associate professor of psychiatry at Columbia University in NY, was not involved in the study.

A new study, the largest ever of its kind, may shed light. The difference between the brains of those who have ADHD and those of the ones who don't is small. These areas are primarily involved in processing emotions and shed new light on some of the non-thinking aspects of ADHD.