Dosing ADHD Medications: Size Matters

A new study suggests that higher doses of ADHD stimulant medications may actually impair working memory. What every parent needs to know about the treatment trade off between hyperactivity and executive function.
The Experts | posted by ADDitude Editors

If you are a parent of an ADHD child who no longer loses sleep or wrings your hands over the fact that he is taking ADHD medication, a new study on attention-deficit meds won’t necessarily send you back down the rabbit hole of worry, but it will make a parent wonder.

Researchers at the University of Wisconsin-Madison performed studies on three monkeys who were given different doses of methylphenidate. The monkeys were taught to look at a target "dot" on a computer screen while another flashed by.

Lower doses of the drug seemed to boost the monkeys’ ability to learn, according to the study, published in the Journal of Cognitive Neuroscience a couple of weeks ago. Higher doses adversely affected the monkeys’ learning quotient and working memory, but did reduce their hyperactivity. "The monkeys on higher doses stuck with the task, but kept making the same errors."

When the researchers looked at whether the medication improved working memory even at lower doses, they found, surprisingly, that it didn’t. "Memory didn’t get better at lower doses and was slightly worse at higher doses," says Luis Populin, Ph.D., who headed up the study.

"Methylphenidate affects the brain’s executive function," says Bradley Postle, Ph.D., a professor of psychology and an expert on working memory at the University of Wisconsin. "It can create an internal environment that, depending on the dose, is either more or less amenable to memory formation and retention. Apparently, the lower dose of methylphenidate helped create the conditions for success without actually improving memory itself."

Populin says the study shows that finding the right dosage of ADHD meds is important for children and adults. Doctors who are trying to reduce hyperactivity in their patients with high doses of methylphenidate might be compromising the patient’s cognitive ability.

Although a parent’s work is never done, discussing your child’s dose level should be added to your to-do list. It could make a big difference in your child’s life at school.

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