Children with ADHD may have "faulty" time management
09 June 2009
Katya Rubia of the Institute of Psychiatry at King's College London and her team have reported that many of the typical behavioural problems in children with attention-deficit hyperactivity disorder (ADHD) could be related to problems in timing functions such as abnormal perception and reduced forward thinking.
'What to most of us seems like a short stretch of time would drag unbearably for someone with ADHD', says professor Rubia. Her team's research shows that children with ADHD have reduced activation in brain areas that are known to be important for timing processes. Brain abnormalities were observed during a series of timing tests in different temporal domains, ranging from the discrimination of milliseconds, perception of seconds, to the sensitivity to tolerate delays of weeks and years.
The research adds to growing evidence for the importance of time perception and other temporal processes in a wide range of psychological disorders, in particular those with impulsiveness-related problems.
ADHD is characterised by an abnormality of dopamine, which is known to affect time perception. Rubia and her colleagues wanted to know if typically reduced brain activation in children with ADHD during time perception could be normalised with the stimulant drug Methylphenidate that is known to enhance dopamine in the brain.
The researchers used MRI scans to show that 12 boys with ADHD had less activity than healthy children during the time discrimination in the frontal lobe, the basal ganglia and the cerebellum, all areas of the brain known to be crucial for time perception. These boys also made more errors than 12 other boys at discriminating the differences in ms between circles that appeared on a screen.
When they were given the drug Methylphenidate (also known as 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 and therefore seems to lead to a complete normalisation of all brain abnormalities' concludes Professor Rubia. The results are published in a special issue of Philosophical Transactions of the Royal Society B, which is devoted to time perception.
Faulty time perception could be related to 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 use these behaviours as a way of 'self-medicating' with dopamine.