Stimulant medication like Ritalin and Adderall are often given to children with ADHD. In the United States, about 3.5 million children between 3 and 17 years old take these medicines, and the number keeps growing as more children are diagnosed.
Most people think the drugs help children pay attention better, but new research shows that this is not exactly how they work.
A large study from Washington University School of Medicine (WashU Medicine) found that these medicines do not directly change the parts of the brain that control attention. Instead, the drugs make the brain feel more awake and make tasks feel more interesting.
When a child feels more alert and finds a task more rewarding, it becomes easier to stay with that task, even though their basic ability to focus has not changed.
ADHD, stimulants, and focus
For many years, clinicians and researchers believed stimulants helped children focus by strengthening brain regions responsible for attention control.
Dr. Benjamin Kay, an assistant professor of neurology at WashU Medicine, noted that this view shaped his own medical training.
“I prescribe a lot of stimulants as a child neurologist, and I’ve always been taught that they facilitate attention systems to give people more voluntary control over what they pay attention to,” said Dr. Kay. “But we’ve shown that’s not the case.”
Instead of seeing changes in attention networks, the research team observed the strongest effects in areas related to arousal and reward.
These regions influence how awake the brain feels and how worthwhile an activity appears, both of which strongly affect behavior.
ADHD medications change the brain
To understand how stimulants change brain activity, the researchers analyzed resting state functional MRI data from 5,795 children aged eight to eleven who participated in the Adolescent Brain Cognitive Development study (ABCD Study).
Resting state scans measure brain activity when no specific task is being performed, allowing researchers to examine underlying brain organization.
Children who took stimulants on the day of scanning showed increased activity in brain regions linked to wakefulness and reward. In contrast, regions classically associated with attention did not show significant changes.
The pattern appeared consistently across the large dataset. Dr. Kay explained why this matters for how improvement is interpreted.
“Rather, the improvement we observe in attention is a secondary effect of a child being more alert and finding a task more rewarding, which naturally helps them pay more attention to it,” he said.
Same effect in adults
The research team validated these results in a controlled experiment involving five healthy adults who did not have ADHD and did not regularly take stimulant medication.
Each participant underwent resting state brain scans before and after taking a dose of methylphenidate.
Once again, the medication altered arousal and reward related brain networks rather than attention circuitry.
This confirmation helped rule out explanations tied only to childhood development or ADHD diagnosis.
Motivation drives improvement
“Essentially, we found that stimulants pre-reward our brains and allow us to keep working at things that wouldn’t normally hold our interest – like our least favorite class in school, for example,” said study senior author Dr. Nico U. Dosenbach.
This increase in perceived reward helps explain why stimulant medications often improve persistence and reduce hyperactivity. Tasks that once felt unrewarding no longer trigger the urge to disengage.
“These results also provide a potential explanation for how stimulants treat hyperactivity, which previously seemed paradoxical,” noted Dr. Dosenbach. “Whatever kids can’t focus on – those tasks that make them fidgety – are tasks that they find unrewarding.”
Sleep affects ADHD stimulant benefits
Sleep emerged as a critical factor in the study. Many children in the dataset did not get the recommended nine or more hours of sleep each night. Short sleep duration was linked to poorer school grades and altered brain connectivity.
Children with ADHD who took stimulant medication performed better academically than peers with ADHD who did not take stimulants.
Children who slept too little but took stimulants also showed better grades than sleep-deprived children who did not take medication.
“We saw that if a participant didn’t sleep enough, but they took a stimulant, the brain signature of insufficient sleep was erased, as were the associated behavioral and cognitive decrements,” said Dr. Dosenbach.
Reevaluating ADHD medications
The experts emphasized that stimulants cannot replace healthy sleep. “Not getting enough sleep is always bad for you, and it’s especially bad for kids,” said Dr. Kay.
He noted that sleep deprivation can mimic ADHD symptoms, including difficulty paying attention and declining school performance.
In some cases, stimulant medication may appear to help by mimicking the effects of adequate sleep while leaving the long term consequences of sleep loss unaddressed.
The findings suggest a shift in how stimulant medications should be understood. Rather than directly improving attention, these drugs increase alertness and make tasks feel more rewarding.
That combination can improve persistence and performance, especially in children with ADHD or those who do not get enough sleep.
By separating attention from arousal and motivation, this research offers a clearer explanation for how stimulant medications shape behavior and brain activity.
The study is published in the journal Cell.
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