For millions of families suffering with attention deficit hyperactivity disorder (ADHD), prescription stimulants like Ritalin and Adderall have become an everyday part of childhood. In the United States alone, around 3.5 million children ages three to seventeen use ADHD medication, a figure that has progressively increased as the disorder has been diagnosed more frequently. 

For decades, experts assumed that these medications worked by directly strengthening the brain's attention networks. A new study, however, reveals that the assumption may be incorrect. 

According to researchers at Washington University School of Medicine in St. Louis, stimulant medicines largely affect the brain's reward and wakefulness centres, rather than the areas normally associated with attention. The findings, published on December 24 in the journal Cell, provide a new reason for why these drugs appear to benefit so many children in classrooms. 

"I prescribe many 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 Benjamin Kay, who handles patients at St Louis Children's Hospital. "But we've shown that's not the case." 

Instead, Kay explained that stimulants appear to increase children's alertness and make things more enjoyable. "The improvement we observe in attention is a secondary effect of a child being more alert and finding a task more rewarding," according to him. 

The researchers examined brain scans from approximately 5,800 children ages eight to eleven who participated in the big Adolescent Brain Cognitive Development (ABCD) Study. Researchers used resting-state functional MRI, a scan that shows how the brain works when a person isn't doing anything specific, to compare children who had taken stimulant medicine on the day of the scan to those who hadn't. 

The change was remarkable. Children given stimulants showed increased activity in brain regions associated with arousal and reward but not in conventional attention centres. Similar patterns emerged when five healthy individuals were scanned before and after taking a stimulant. 

"Essentially, we discovered that stimulants pre-reward our brains and allow us to continue working on tasks that would not normally interest us," said Dr Nico Dosenbach, one of the study's senior authors. 

For parents, the findings may explain why a youngster who previously fidgeted throughout lessons may now sit still and complete schoolwork. Tasks that were once boring may now feel easier to tolerate. 

The study also raises several crucial sleep-related problems. Children with ADHD who slept less than the prescribed nine hours per night fared better when given stimulants, implying that the medications may disguise the effects of sleep deprivation. However, the result disturbs clinicians. 

"Not getting enough sleep is always bad for you, and it's especially bad for kids," Kay told me. He said weary children can exhibit ADHD-like symptoms, risking misdiagnosis while the true problem — a lack of sleep — remains ignored. 

According to the researchers, longer-term studies are needed to determine whether using stimulants to compensate for poor sleep has long-term impacts on the developing brain.