Stimulant medications are an effective treatment for Attention-Deficit/Hyperactivity Disorder (ADHD). In the classroom, parents and teachers say that medications like methylphenidate (MPH) can reduce symptoms and improve behavior.

Although stimulants have been in use for decades to treat ADHD in school-aged children, just how they work hasn't been clear. The new study in the Journal of Child Psychology and Psychiatry is filling in critical gaps about the role of improved cognitive functions.

This is the first study to demonstrate that improving short-term working memory and the ability to inhibit are at least part of the way that stimulants work and improve outcomes for ADHD in the classroom.

Knowing how frontline treatments like MPH work can help develop better treatments, both pharmacological and behavioral, that target certain mechanisms and processes or contribute to developing equally effective pharmacotherapies with fewer side effects than those currently in use.

It's estimated that it takes 15 to 20 years to go from animal research to an approved medication, at the cost of roughly $500 million to $2 billion. Knowing how one treatment works gives us clues about what to target in developing new treatments. That can save a lot of time, energy and money.

Stimulant Treatment

Hawk says researchers often have a good hypothesis to explain the efficacy of certain medications, but for many treatments, their workings remain a mystery. In the case of stimulant treatment of ADHD, improved classroom behavior and seatwork completion are well-documented clinical benefits.

To provide a more definitive test of the idea, the researchers combined the clinical and laboratory worlds to examine basic cognition and clinical outcomes in the same children at the same time. 

Cognitive Abilities

In small groups over three summers, the study's 82 children ages 9-12 completed a one-week summer program. The children completed a range of activities, including sports and games, arts and crafts, three math classes, and computerized assessments of their cognitive abilities.

On each day, each child received either a placebo or a low or moderate dose of stimulant medication. The researchers looked at how well children's response to medication on the cognitive tasks accounted for how much the medication improved their classroom behavior and some math problems solved.

The results provide the strongest evidence to date that stimulants like methylphenidate improve classroom behavior and performance by enhancing specific cognitive processes.  Specifically, the more medication helped kids hold and manipulate information in working memory and the more it helped children inhibit responses 'on the fly,' the greater the classroom benefit. These data are the strongest yet to suggest those are the mechanisms by which the medication is working.

Novel Medications

When discussing how the findings might contribute to new treatments, Hawk points out that this work could guide the search for novel medications.  Behavioral treatment and parent training may strengthen these cognitive processes indirectly. Both can be used to enhance executive function and behavior by systematically and gradually reinforcing greater and greater self-control. 

They hope that we and others are now able to take those next steps and turn these novel findings into even more practical outcomes for families.