The trouble concentrating that affects people with attention-deficit hyperactivity disorder (ADHD) might be related to motivation, a new study has found.
The motivational problems seen with the condition, which is often associated with children but can persist into adulthood, appear to stem from a reduction in dopamine, an important neurotransmitter in the nervous system that is considered a hallmark of ADHD.
"ADHD is traditionally a disease where people think the disruption is in attention and hyperactivity," said Dr Nora D. Volkow, director of the US National Institute on Drug Abuse and lead researcher on the study. "So, the whole focus on research and treatment has been on attention -- with kids who cannot pay attention or are hyperactive."
Recent studies have found that children with ADHD don't respond to rewards in the same way as children without ADHD, Volkow said. "In addition to the classic symptoms of inattention and hyperactivity, there is also a disruption in motivations and sensitivity to rewards," she said.
Findings could alter future treatments
The new study "found a disruption in the brain's reward/motivation pathway" in people with ADHD, Volkow said. "We also found that disruption in this area was directly related to the severity of inattention."
The implication of the finding is that ADHD might begin with disruption in motivation, which in turn leads to inattention and hyperactivity, she said. Volkow described it as "a disruption in interest."
The finding, reported in the Journal of the American Medical Association, could have an impact on treating the condition, she said. "My strategy would be rather than exercising the attention network, let me give an intervention that will make the task much more engaging," she said.
How the study was done
For the study, 53 adults with ADHD underwent positron emission tomography (PET) scans for dopamine markers. The researchers compared the results with PET scans of 44 adults without the condition.
Among those with ADHD, the researchers found disruptions in the two dopamine pathways associated with reward and motivation. The finding, according to the researchers, lends support to the theory that ADHD is a result of problems in dopamine pathways in the brain that affect both reward and motivation.
About 3% to 5% of adults in the United States have some form of ADHD, the researchers noted. The current medications given to children with ADHD already enhance motivation because they target the dopamine pathway, Volkow said.
But the finding should also be considered a "wake-up call for teachers," she said. Knowing that the problem is one of motivation, teachers could devise methods to provide "extra engagement" for these children, Volkow said.
Dopamine deficiency may lead to ADHD
Even children with ADHD can concentrate on tasks they like and find engaging, such as computer games, she noted. The trick is to bring that same level of engagement into the classroom, she said.
"It's a great opportunity to develop curriculum that is much more exciting and engaging for kids suffering from ADHD," Volkow said.
Dr Andrew Adesman, chief of developmental and behavioural paediatrics at Schneider Children's Hospital in New York, said the study "provides further evidence that dopamine deficiencies in specific areas of the mid-brain are likely responsible for ADHD."
"Since many believe that ADHD results from reward and motivational deficits, this study provides further support for this association," he said.
"Patients and professionals must recognise, however, that despite research advances identifying differences in the brains of patients with ADHD, the diagnosis of ADHD remains a clinical one," Adesman said. "ADHD cannot be diagnosed by neuroimaging." – (HealthDay News, September 2009)
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