Around 75% of children and adults with Attention Deficit Hyperactivity Disorder (ADHD) also have sleep problems, but until now these have been thought to be separate issues. Now a in a pulling together of the latest research, Scientists are proposing of a new theory which says that much of ADHD may in fact be a problem associated with lack of regular circadian sleep.

Presenting the proposal at the ECNP Conference in Paris, Professor Sandra Kooij (Associate Professor of Psychiatry at VU University Medical Centre, Amsterdam and founder and chair of the European Network Adult ADHD) said:

"There is extensive research showing that people with ADHD also tend to exhibit sleep problems. What we are doing here is taking this association to the next logical step: pulling all the work together leads us to say that, based on existing evidence, it looks very much like ADHD and circadian problems are intertwined in the majority of patients.

We believe this because the day and night rhythm is disturbed, the timing of several physical processes is disturbed, not only of sleep, but also of temperature, movement patterns, timing of meals, and so on.

If you review the evidence, it looks more and more like ADHD and sleeplessness are 2 sides of the same physiological and mental coin."

Professor Kooij laid out the links which have led to the synthesis:

• In 75% of ADHD patients, the physiological sleep phase -- where people show the physiological signs associated with sleep, such as changes in the level of the sleep hormone melatonin, and changes in sleep-related movement -- is delayed by 1.5 hours.

• Core body temperature changes associated with sleep are also delayed (reflecting melatonin changes)

• Many sleep-related disorders are associated with ADHD, including restless-leg syndrome, sleep apnea, and the circadian rhythm disturbance, the delayed sleep phase syndrome

• ADHD people often show greater alertness in the evening, which is the opposite of what is found in the general population

• Many sufferers benefit from taking melatonin in the evening or bright light therapy in the morning, which can help reset the circadian rhythm

• Recent work has shown that around 70% of adult ADHD sufferers show an oversensitivity of the eyes to light, leading many to wear sunglasses for long periods during the day -- which may reinforce the problems associated with a 'circadian shift'.

• Chronic late sleep leads to a chronic sleep debt, associated with obesity, diabetes, cardiovascular disease and cancer. This cascade of negative health consequences may in part be preventable by resetting the sleep rhythm

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