ADHD medications mimic the effects of a good night’s sleep rather than controlling attention, researchers find

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By Daniel Pye

Stimulant medications for attention deficit hyperactivity disorder (ADHD) primarily work on the brain’s reward and wakefulness centres rather than controlling attention, researchers have found.

It could mean that addressing inadequate sleep is as important as considering medication for children with possible ADHD.

Using functional magnetic resonance imaging (fMRI) scans of 5,795 children aged between 8 to 11 in the United States, the team found those who took stimulants showed increased activity in regions of the brain related to arousal or wakefulness and regions predicting how rewarding an activity will be, compared to participants on no stimulants.

The findings, published in Cell, suggest that stimulant medications produced patterns of brain activity that mimicked the effect of good sleep, negating the effects of sleep deprivation on brain activity.

Prescription stimulants also enhance performance by making individuals more alert and interested in tasks, the team at the Washington University School of Medicine in St. Louis, US found.

Assistant professor of neurology Benjamin Kay, who treats patients at St Louis Children’s Hospital, said: “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.

“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.”

The findings point to the importance of addressing inadequate sleep as well as considering medication for children being evaluated for ADHD, he said.

Stimulants ‘pre-reward our brains’

The children selected for the research were participants in the Adolescent Brain Cognitive Development (ABCD) Study, which tracks the neurodevelopment of more than 11,000 children from across the US.

After analysing the child fMRI scans, the researchers then observed five healthy adults without ADHD who normally did not take stimulant medication.

These participants were scanned using resting-state fMRI scans before and after taking a dose of stimulant medication. The researchers again found that arousal and reward centres in the brain, not attention centres, were activated by the medications.

Nico U. Dosenbach, professor of neurology, said that stimulants “pre-reward our brains”, allowing people to keep working at things that do not hold their interest, such as their least favourite class in school.

Stimulant drugs help make activities a child normally struggles to focus on feel relatively more rewarding, he said.

“These results also provide a potential explanation for how stimulants treat hyperactivity, which previously seemed paradoxical,” Prof Dosenbach added.

“Whatever kids can’t focus on — those tasks that make them fidgety — are tasks that they find unrewarding. On a stimulant, they can sit still better because they’re not getting up to find something better to do.”

Children with ADHD who took a stimulant medication received better grades in school, their parents said, and performed better on cognitive tests given as part of the ABCD study.

Not getting enough sleep is ‘always bad for you’

Children who got less than the recommended nine or more hours of sleep per night and took a stimulant received better grades in school than those who got insufficient sleep and did not take a stimulant.

But stimulants did not correspond with improved performance for neurotypical children who got sufficient sleep (it is unclear why they were taking medications, the researchers said). Stimulants were linked with improved cognitive performance only for participants with ADHD or those who got 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 behavioural and cognitive decrements,” Prof Dosenbach said.

However, the authors noted that this boost in performance despite a lack of sleep might carry long-term costs.

“Not getting enough sleep is always bad for you, and it’s especially bad for kids,” Kay said.

Children who are overtired may exhibit classic symptoms of ADHD, such as difficulty paying attention in class or declining grades, leading to a misdiagnosis in some cases when the real culprit is sleep deprivation.

The stimulant medication may then appear to help by mimicking some of the effects of a good night’s sleep, while still leaving the child vulnerable to long-term effects of sleep deprivation. Kay urged doctors to consider sleep deprivation as a factor in ADHD diagnoses and to explore strategies or treatments to boost kids’ sleep.

The researchers called for future studies on the potential long-term effects of stimulants on brain function.

They noted that these medications could have a restorative effect by activating the brain’s waste clearing system during wakefulness, but it is equally likely they might cause lasting damage if used to cover up chronic sleep deficits.

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