ADHD drugs boost alertness, reward perception rather than focus: Study

New Delhi: Prescription medicines used to treat ADHD may be working by making one more alert and interested in tasks, rather than directly improving their ability to focus as was previously thought, a new study has found.

Attention deficit hyperactivity disorder is a neurodevelopmental condition, marked by short attention spans and restless, impulsive behaviour.

Stimulant drugs — available in India under market names such as Addwise — prescribed by a psychiatrist as treatment are thought to work by increasing levels of chemicals in the brain, including norepinephrine and dopamine, thereby improving focus and control on impulses.

MRIs of 5800 children aged 8 to 11 analysed

Researchers, including those from Washington University, US, analysed functional magnetic resonance imaging (fMRI) scans from nearly 5,800 children aged 8 to 11, showing brain activity when they were not engaged in a task.

Results published in the journal Cell show for the first time that stimulant medicines act primarily on the brain regions important for reward and wakefulness, rather than those responsible for attention, the team said.

The medications were also found to produce brain activity that mimicked effects of a good sleep, negating those due to sleep deprivation — children with ADHD are known to suffer from sleep disruption, such as difficulty falling asleep and restless sleep.

“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 favourite class in school, for example,” co-lead researcher Nico U. Dosenbach, professor of neurology at Washington University’s school of medicine, said.

Co-lead researcher Benjamin Kay, a paediatric neurologist and assistant professor at Washington University’s school of medicine, 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,” Kay said.

Kay added that the study’s findings point to the importance of addressing inadequate sleep in addition to considering stimulant medication for children being evaluated for ADHD.

Study compared patterns of brain connectivity

The study compared patterns of brain connectivity between children who took prescription stimulants and those who did not on the day of their scan. The participants are part of a larger Adolescent Brain Cognitive Development (ABCD) study, which is tracking more than 11,000 children across the US.

“Taking stimulants reversed the effects of sleep deprivation on connectivity and school grades. Connectivity was also changed in salience and parietal memory networks, which are important for dopamine-mediated, reward-motivated learning, but not the brain’s attention systems,” the authors wrote.

Effect of stimulant medication

Compared with children having ADHD who did not take a stimulant, children with ADHD who took a stimulant medication were found to have better grades in school (reported by parents) and performed better on cognitive tests taken as part of the study.

Children with more severe ADHD showed the greatest gains in cognitive outcomes associated with taking prescription stimulants, the researchers said.

However, stimulant medications were not associated with cognitive gains in all children taking them — taking the drugs did not correspond with improved performance for neurotypical kids who got sufficient sleep, the team said.