For decades, ADHD stimulant medications have been thought to sharpen attention, but new research has uncovered something very different is at play. These drugs don't actually provide laser-sharp focus but may instead boost wakefulness and engagement, helping the brain stay with tasks rather than hold attention.
In a landmark study, scientists at Washington University School of Medicine in St. Louis (WashU) have shown for the first time that stimulant medications mainly act on the brain’s reward and wakefulness centers, rather than on its attention circuitry. This upends traditional thought on how drugs like Adderall and Ritalin work.
Essentially, attention-deficit/hyperactivity disorder (ADHD) stimulants aren't a silver bullet for focus, but affect the reward and wakefulness part of the brain to supplement "interest" in tasks. While this can be perceived as focus, brain scans revealed that it is instead a roundabout way to provide focus.
What's more, the researchers found that stimulant medications produced patterns of brain activity that were representative of quality sleep – something that is often hard for people with ADHD to achieve.
“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 Brendan Kay, assistant professor of neurology, who treats patients at St. Louis Children’s Hospital. “But we’ve shown that’s not the case. 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.”
Showing the shift from self-reporting and survey data to brain imaging in ADHD studies, the researchers looked at resting-state fMRI scans of more than 11,000 individuals in the Adolescent Brain Cognitive Development (ABCD) Study. These scans measure how different regions of the brain communicate when a person is not actively performing a task. The team compared the scans of brains on days when ADHD individuals had taken their medications with days that they hadn't. To determine whether the effects were specific to ADHD, the team also conducted a smaller follow-up experiment in adults without ADHD, administering stimulant medication and scanning their brains.
What they found was that kids who took stimulants the day of the scan showed a boost of activity in the regions of the brain related to arousal or wakefulness and reward anticipation. In the adults, the team again found that arousal and reward centers were activated, not attention centers.
“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 Nico U. Dosenbach, MD, a professor of neurology. “These results also provide a potential explanation for how stimulants treat hyperactivity, which previously seemed paradoxical.
"Whatever kids can’t focus on – those tasks that make them fidgety – are tasks that they find unrewarding," he added. "On a stimulant, they can sit still better because they’re not getting up to find something better to do.”
As someone with ADHD who is on two types of stimulants, no drug in the world could make me sit down and focus on doing my taxes or doing anything else I have no interest in doing. So anecdotally, this backs what I've felt for years: The medication doesn't help with focus, and if you sleep poorly it's even more of a struggle, but it increases your capacity to stick with things you find interesting – which can be exhausting otherwise.
However, the power of stimulants may lie in the support role they play for ADHD people who have consistently poor sleep. This study showed how the drugs boosted people's cognitive function to mirror that of those who had quality sleep, while stimulants had no effect on the brains of neurotypical participants. Basically, stimulants were linked with improved cognitive performance – but only for those with ADHD who had insufficient sleep.
“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,” Dosenbach said.
This may be an important part of stimulant medication, however, as sleep disturbance and poor nighttime routines come hand-in-hand with ADHD. Together, the findings suggest that stimulant medications may help indirectly by reducing the mental effort required to stay engaged with tasks at hand, rather than by directly increasing focus. This also offers a biological explanation for why many people report that these medications make tasks feel more manageable and less overwhelming, without necessarily making concentration effortless. It also helps explain why stimulants often feel far less effective when someone has had a bad night's sleep (I can again attest to this).
By shifting the focus away from attention alone and toward arousal, motivation and readiness to engage, this groundbreaking study challenges traditional views of ADHD and stimulant medication, and may help inform future treatments.
The researchers note that we need more studies on the potential long-term effects of stimulants on cognitive function, especially if the day-to-day offsetting of poor sleep is masking a lack of restorative rest that could potentially lead to chronic conditions down the line. Although the brain scans came primarily from children, the researchers confirmed the results in adults, strengthening the findings beyond childhood ADHD.
"Attention is a multifaceted construct that is difficult to operationalize from behavioral studies alone," the researchers concluded. "Performance on attention-demanding tasks is influenced not only by cognitive ability and allocation of attention but also by arousal, vigilance, motivation, effort, and persistence or drive. Using rs-fMRI, we showed that stimulants mimic the effects of sleep (arousal) and reward expectation (salience) consistent with boosting drive, not top-down allocation of attention nor cognitive ability."
The study was published in the journal Cell.
