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 scientists are proposing a theory that says much of ADHD may in fact be a problem associated with lack of regular circadian sleep.

Sandra Kooij, MD, PhD, associate professor of psychiatry at VU University Medical Centre, Amsterdam, and founder and chair of the European Network Adult ADHD, presented an abstract on this topic at the recent ECNP Conference in Paris. Kooij says in a release, “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.”

Kooij noted these links:

  • 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 of delayed sleep phase syndrome.
  • People with ADHD often show greater alertness in the evening, which is the opposite of what is found in the general population.
  • 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.

Kooij says, “We are working to confirm this physical-mental relationship by finding biomarkers, such as vitamin D levels, blood glucose, cortisol levels, 24-hour blood pressure, heart rate variability, and so on. If the connection is confirmed, it raises the intriguing question: Does ADHD cause sleeplessness, or does sleeplessness cause ADHD? If the latter, then we may be able to treat some ADHD by non- pharmacological methods, such as changing light or sleep patterns, and prevent the negative impact of chronic sleep loss on health.


Andreas Reif, MD, of University Hospital, Frankfurt, and leader of the EU CoCA project on ADHD and who was not involved in the research, says, “A disturbance of the circadian system may indeed be a core mechanism in ADHD, which could also link ADHD to other mental illnesses such as depression or bipolar disorder. But also beyond these pathophysiological considerations, sleep problems and abnormalities of circadian rhythms are a huge problem for many patients, heavily impacting on their social life. More research into the interconnections between ADHD and the ‘inner clock’ is thus very relevant to improve patients’ lives and to shed light on the disease mechanism of ADHD.”

ADHD) is a group of behavioral symptoms with a neurobiological background that include inattentiveness, hyperactivity, mood swings, and impulsiveness. ADHD is highly heritable, and several differences in brain volume and function have been shown compared to controls. Symptoms of ADHD tend to be noticed at an early age and may become more noticeable when a child’s circumstances change, such as when they start school. Most cases are diagnosed when children are 6 to 12 years old, but ADHD is also increasingly recognized in adults and older people, as ADHD can persist during the lifespan. People with ADHD often have additional problems, such as sleep, mood- and anxiety disorders.