ADHD Drug Changes Kids' Brains, Maybe for the Better

F. Perry Wilson, MD, MSCE


August 14, 2019

Welcome to Impact Factor, your weekly fraction of commentary on a new medical study. I'm Dr F. Perry Wilson.

This week, a new study suggests that methylphenidate (Ritalin) changes the brains of kids with attention-deficit/hyperactivity disorder (ADHD).

Cue a lot of nervous parents waking up in a cold sweat at 3 AM. And no doubt a flurry of calls to our pediatric colleagues.

This was a small but high-quality study appearing in the journal Radiology.[1]

Fifty boys aged 10-12 years and 48 men aged 23-40 with a psychiatrist-confirmed diagnosis of ADHD were randomized to receive methylphenidate or placebo for about 4 months. Before starting treatment and 1 week after stopping treatment, they got a brain MRI with diffusion-weighted imaging. A previous report of this cohort[2] showed clinical improvement with methylphenidate, but the important question in this study is, why?

Based on prior animal studies, the researchers hypothesized that they might see changes in white matter structure in the brain, as evidenced by differences in fractional anisotropy.

Source: Radiological Society of North America

What the heck is fractional anisotropy? As a nephrologist who gets accidental calls looking for neurologists all the time... I had no idea. But after chatting with a few real neurologists, I learned that it integrates a variety of information about white matter. More myelination increases fractional anisotropy; more structured axonal orientation also increases fractional anisotropy.

So, does methylphenidate affect fractional anisotropy? Not too much, at least in the areas the researchers were focusing on.

Source: Radiological Society of North America

Over time, there was no significant change in fractional anisotropy in the entire brain or in preidentified regions of interest. Nor was there a significant effect of methylphenidate on fractional anisotropy in those regions.

But... the fractional anisotropy response to methylphenidate did differ significantly between the boys and the men, such that within the boys, fractional anisotropy increased more in response to methylphenidate than in the men.

Source: Radiological Society of North America

You can see exactly where in the brain that change was most dramatic in this neat picture highlighting the left superior longitudinal fasciculus and some other areas rich in crossing fibers.

Source: Radiological Society of North America

OK, I don't need an MRI to see what you're thinking. What does this mean?

I asked lead author Liesbeth Reneman whether increasing fractional anisotropy is a good thing in this situation.

She wrote that she can't be sure, but that in longer follow-up, she "expect[s] to find that the fractional anisotropy changes...are positive."

In the end, the results here should be reassuring for our patients with ADHD and especially their parents. We probably aren't warping fragile minds too much with Ritalin, and it may even be helping. For the parents of kids who have seen dramatic improvements in attention thanks to methylphenidate, this study should help them sleep a bit better at night.


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