By Alice Klein
A DRUG normally used to treat narcolepsy and excessive daytime sleepiness also seems to improve symptoms of attention deficit hyperactivity disorder (ADHD) symptoms. The finding supports the idea that ADHD might be a sleep disorder.
People who have been diagnosed with ADHD find it difficult to concentrate and are generally hyperactive. But many with the condition also find it difficult to fall asleep and stay asleep at night, and feel drowsy during the day.
Could this mean ADHD is a type of sleep disorder? After all, the brain pathways involved in paying attention have also been linked to sleep. And there’s some evidence of similarly disrupted patterns of chemical signalling in the brains of people with sleep disorders and ADHD.
One suggestion is that the circadian rhythm that controls our sleep-wake cycle over each 24 hour period may be misaligned in people with ADHD, causing them to be sleepy or alert at the wrong times.
This idea inspired Eric Konofal at Robert-Debré Hospital in Paris to try using a drug for narcolepsy and excessive daytime sleepiness to treat ADHD.
Mazindol mimics the effects of a brain chemical called orexin, which modulates wakefulness and appetite. It works as a stimulant to keep us awake, and is lacking in people with narcolepsy, who tend to fall asleep at inappropriate times.
In their clinical trial, Konofal and his colleagues gave either mazindol or a placebo to 85 adults aged between 18 and 65, all of whom had previously been diagnosed with ADHD. Within two weeks, ADHD symptoms had reduced by more than 50 per cent in just over half of those who tried the drug.
These results are better than those in trials using conventional ADHD drugs, such as Ritalin and Adderall, says Daryl Efron at Murdoch Childrens Research Institute in Melbourne. Future trials should directly compare the effects of these drugs with mazindol, to see if it really is superior, says Efron. “But it does look like it could be a very promising additional treatment option for people with ADHD,” he says.
Mazindol is the first new ADHD drug for decades to work in a novel way, says Efron. “Since mazindol acts on a different neurochemical pathway, it could be useful for those who don’t respond to existing treatments.”
The drug also appears to be safe, although some participants in the trial developed minor side effects such as constipation and nausea. These symptoms were most probably due to its effect on appetite – mazindol has previously been used as a weight loss drug because it reduces feelings of hunger.
However, although mazindol improved many ADHD symptoms, it did not boost the quality of the volunteers’ sleep, nor reduce the daytime sleepiness they experienced. The team is planning larger trials and other experiments to better understand how the drug might be working.
This article appeared in print under the headline “Narcolepsy drug suggests ADHD is a sleep disorder”
narcolepsy: a medical condition that makes you go to sleep suddenly and when you do not expect it
hyperactive: Someone who is hyperactive has more energy than is normal, gets excited easily, and cannot stay still or think about work
drowsy: being in a state between sleeping and being awake
circadian: used to describe the processes in animals and plants that happen naturally during a 24-hour period
mimic: to copy the way in which a particular person usually speaks and moves, usually in order to make people laugh
placebo: something that is given to try to satisfy a person who has not been given the thing they really want
constipated: unable to empty your bowels as often as you should