Attention-deficit hyperactivity disorder (ADHD) stimulants, prescription drugs including methylphenidate (Ritalin) and mixed amphetamine salts (Adderall), primarily affect brain circuits governing arousal and reward rather than the attention networks long assumed to be their main target, according to a neuroimaging study by Kay and colleagues at Washington University in St. Louis published in Cell in December 2025. The finding, drawn from resting-state functional magnetic resonance imaging (fMRI) in a large cohort of children plus a controlled adult imaging trial, complicates the standard model in which stimulants sharpen attention circuits directly and suggests that improved focus is a downstream consequence of heightened alertness and motivational salience.
Stimulants are the most-prescribed ADHD treatment for a reason
Prescription stimulants have been used to treat what is now called ADHD since Charles Bradley reported in 1937 that amphetamine appeared to help “behavioral problem children.” The class has been the first-line pharmacological treatment for ADHD across the lifespan since large-scale prescribing began in the 1970s. Randomized trials and meta-analyses consistently place stimulant response rates around 70%, higher than any other class of ADHD medication. The Faraone consensus statement, drawing on studies covering more than 2,000 participants each, confirms this as one of its most robust findings.
The standard model has been that stimulants directly sharpen attention circuits
Methylphenidate and amphetamine salts both block the presynaptic transporters that reabsorb dopamine and norepinephrine, leaving more of each neurotransmitter in the synaptic cleft. The standard textbook explanation has been that this action, concentrated in the prefrontal cortex, strengthens executive control and attention networks that are underactive in ADHD. Prior neuroimaging studies produced mixed and often conflicting evidence for that model, with some finding stimulant effects on executive control regions and others finding no such effect.
The 2025 Cell study reframes the mechanism
Kay and colleagues analyzed resting-state fMRI data from the Adolescent Brain Cognitive Development (ABCD) Study, a large cohort of US children, comparing those who took stimulants on the day of their brain scan with those who did not. They then validated the pattern in a controlled precision imaging drug trial in five adults without ADHD who received stimulant medication and were scanned before and after dosing.
In both cohorts, stimulants changed connectivity in brain regions associated with arousal and wakefulness, and in salience network regions that predict how rewarding an activity will feel. Attention networks in the conventional sense showed no significant change. Nico Dosenbach, one of the senior investigators, framed the result to journalists at the study’s release: “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.”
The clinical implications are subtle
For patients who benefit from stimulant medication, the reframing does not change the fact that the medications work. What it does suggest is that some of the well-known side effects of stimulants (elevated heart rate, reduced appetite, insomnia, anxiety) may be inherent to their arousal-and-reward mechanism rather than incidental to a more targeted attention effect. It also gives a mechanistic explanation for something long observed clinically: stimulants produce performance benefits in people without ADHD. If the mechanism is primarily arousal and reward salience, the drugs would be expected to help anyone doing sustained, low-intrinsic-motivation work, regardless of whether they have ADHD. That does not make them safe or advisable for that use.
Non-stimulant options are also part of the ADHD toolkit
Not everyone responds to stimulants, and not everyone should take them. Atomoxetine, a selective norepinephrine reuptake inhibitor, is the main non-stimulant approved for ADHD. Alpha-2 agonists (guanfacine and clonidine) are also used, particularly in children with tic disorders or sleep problems. Response rates for non-stimulants are lower than for stimulants, and behavioral interventions, especially for children and for adults with comorbid anxiety or depression, remain evidence-based components of comprehensive care.
What the evidence cannot yet answer
The Cell 2025 study is the largest of its kind but does not yet demonstrate that the arousal-and-reward mechanism explains all of stimulants’ clinical effect. Whether targeted drugs that engage attention networks more selectively could offer benefit with fewer arousal-related side effects is an open question. The long-term neurodevelopmental effects of stimulant treatment in children remain incompletely characterized, and the sharp rise in ADHD diagnosis and treatment over recent decades, especially in adults, is not fully explained by better recognition alone. As the Faraone consensus statement notes, misdiagnosis in both directions remains a real problem, and the balance between under-treatment and over-treatment continues to be actively debated.
References
- Kay BP, Wheelock MD, Siegel JS, et al. Stimulant medications affect arousal and reward, not attention networks. Cell, 2025. DOI: 10.1016/j.cell.2025.11.039
- Faraone SV, Banaschewski T, Coghill D, et al. The World Federation of ADHD International Consensus Statement: 208 Evidence-based conclusions about the disorder. Neuroscience and Biobehavioral Reviews, 2021; 128: 789-818. DOI: 10.1016/j.neubiorev.2021.01.022
- National Institute of Mental Health. Attention-Deficit/Hyperactivity Disorder. Available at: nimh.nih.gov
- Cortese S, Adamo N, Del Giovane C, et al. Comparative efficacy and tolerability of medications for attention-deficit hyperactivity disorder in children, adolescents, and adults. The Lancet Psychiatry, 2018; 5: 727-738. DOI: 10.1016/S2215-0366(18)30269-4