What to most of us seems like a short stretch of time would drag unbearably for someone with ADHD, says Katya Rubia of the Institute of Psychiatry at King's College London. Her team's research, reported this week, adds to a growing body of evidence for the importance of time perception in a wide range of psychological disorders.
ADHD affects around 5 per cent of children globally, most of them boys. Studies relating to the disorder have focused on patients' short attention spans and impulsive behaviour. But ADHD is characterised by a shortage of dopamine, which is known to affect time perception, so Rubia and her colleagues wanted to know if this was the source of the kids' problems.
The researchers used MRI scans to show that 12 boys with ADHD had less activity than usual in the frontal lobe, the basal ganglia and the cerebellum, all areas of the brain known to be crucial for time perception. These boys were also worse than 12 other boys at estimating how long circles appeared on a screen before vanishing.
When they were given the drug methylphenidate, aka Ritalin, which boosts dopamine levels and is used to treat ADHD, brain activity in the ADHD group became indistinguishable from that of the healthy boys. "Ritalin enhances brain regions that are important for time perception in ADHD children," concludes Rubia. The results are published in a special issue of Philosophical Transactions of the Royal Society B, which is devoted to time perception (DOI: 10.1098/rstb.2009.0014).
Rubia believes this is evidence that faulty time perception causes the major symptoms of ADHD, by making children perceive even short periods of inactivity as inordinately long and boring. Because novelty-seeking and risky behaviour increase dopamine levels, children with ADHD may be become hyperactive as a way of "self-medicating" with dopamine.
Friday, June 12, 2009
Interesting ADHD Research
An interesting hypothesis about yperactivity in boys has been published in New Scientist. The article called, Time moves too slowly for hyperactive boys by Andy Coghlan is worth a read.