Tablets, LED Lighting, Sleep, and Attention Problems

Shining a different light on ADHD and concentration problems

In many schools, children who are easily distracted or diagnosed with ADHD are still routinely placed away from the window. The reasoning seems logical: if a child can already be distracted, surely sitting near a window—where birds fly past and people walk by—will only make things worse.

But what if this assumption is wrong?

What if, for some children, sitting closer to a window is not part of the problem—but part of the solution?

ADHD is usually associated with difficulties in concentration, impulse control, and planning. These challenges are often seen as core features of the condition. But an important question is rarely asked: Are these difficulties always the core problem, or could they sometimes be the result of something else?

In this blog, we explore an alternative perspective—one in which sleep, biological timing, and light exposure play a central role. From this viewpoint, some children who struggle with attention might actually benefit from more daylight exposure, not less.

ADHD Is Not the Same for Every Child

Most parents intuitively know this: no two children are the same. This is just as true for children with concentration problems or diagnosed with ADHD. Despite sharing the same diagnostic label, children can differ greatly in their behavior, underlying biology, and response to treatment.

This becomes particularly clear when treatments are tried. Some children respond well to stimulant medication such as Ritalin. Others benefit more from neurofeedback. Some improve with one approach but not another—and some do not respond well to any standard treatment at all.

These differences strongly suggest that ADHD does not have a single cause. From a neurobiological perspective, it is not one uniform disorder that can be treated effectively with a one-size-fits-all solution.

Only in recent years has this idea begun to gain traction in psychiatry, under the concept of precision psychiatry or personalized medicine. This approach recognizes that psychiatric diagnoses often consist of multiple subtypes, each with different underlying mechanisms. Identifying these subtypes requires the use of biological markers, such as brain activity, sleep patterns, or cognitive profiles.

Looking Beneath the Label: Drowsiness as a Hidden Subtype

At Brainclinics Foundation, research over the past 25 years has focused on identifying such subtypes within conditions like ADHD and depression. This work uses applied brain research methods, including EEG (electroencephalography), neuropsychological testing, and sleep assessments, alongside innovative treatments such as neurofeedback and brain stimulation.

One consistent finding across multiple studies is the existence of a subgroup of children with ADHD whose brain activity shows clear signs of drowsiness or sleepiness. When measured with EEG, their brains resemble those of individuals who are not fully alert.

Interestingly, this subgroup tends to respond particularly well to stimulant medication and to neurofeedback. From a conceptual standpoint, this makes sense: a stimulant medication may be especially effective in individuals whose core problem is under-arousal or drowsiness rather than hyperactivity in the traditional sense.

This insight alone already challenges the stereotypical image of ADHD as a condition of specific attentional problems or “too much energy.” In some children, the opposite may be true.

Neurofeedback, Sleep, and an Unexpected Clue

Neurofeedback is a non-pharmacological treatment in which individuals receive real-time feedback on their brain activity and learn, through practice, to regulate specific brain networks. One well-established form, known as Sensorimotor Rhythm (SMR) neurofeedback, is often associated with improvements in sleep quality as well as reductions in ADHD symptoms such as inattention and impulsivity.

Over many years of clinical work, one observation stood out repeatedly: even when children did not report sleep problems beforehand, one of the most frequently mentioned “side effects” of neurofeedback was better sleep.

This observation raised an important question. If improving brain regulation improves sleep—and improved sleep reduces ADHD-like symptoms—could sleep problems be a key piece of the puzzle?

Based on this and converging scientific findings, a model was proposed more than a decade ago suggesting that sleep disturbances and ADHD-related symptoms such as poor concentration and impulsivity are closely connected.

Sleep Deprivation vs. Sleep Restriction: A Crucial Difference

To understand this relationship, it is important to distinguish between two often-confused concepts: sleep deprivation and sleep restriction.

Sleep deprivation refers to extreme situations, such as staying awake all night. Its effects on mood, attention, and functioning are obvious and immediate.

Sleep restriction, however, is far more subtle—and far more common. It refers to consistently sleeping just 30 to 60 minutes less than needed each night.

This may not sound dramatic, but its long-term effects are profound.

Research shows that when adults are asked to sleep six hours instead of eight for two weeks, their attention and working memory deteriorate significantly. Yet when asked how they feel, they often report no problems at all. Objectively, however, their cognitive performance is comparable to that of someone who has gone two full nights without sleep.

Even more importantly, recovering from chronic sleep restriction is not as simple as “sleeping in” on the weekend. It may take just as many nights of full sleep as the number of nights of restriction to fully recover.

Why This Matters for Children

Large-scale studies consistently show that children who sleep more perform better academically, have stronger executive functions, and display fewer behavioral problems such as impulsivity, restlessness, and defiance.

When healthy children are experimentally exposed to sleep restriction, they begin to show more ADHD-like behavior—even though they do not have ADHD.

This makes one trend particularly alarming: today’s children sleep, on average, over an hour less than children did a century ago.

Objective EEG studies further show that over the past decade, the brains of healthy children display increasing signs of drowsiness. Sleep, clearly, plays a fundamental role in daily functioning—and its gradual erosion may contribute to the rising prevalence of attention problems in modern society.

Sleep Disorders Are Common in ADHD

Children with ADHD are more likely to experience a range of sleep disorders, including restless legs syndrome and sleep-related breathing problems such as snoring or sleep apnea. Importantly, treating these sleep disorders often leads to improvements in ADHD-related behavior.

But the most common—and often overlooked—sleep problem in ADHD is difficulty falling asleep at a developmentally appropriate bedtime. This so-called sleep-onset insomnia affects an estimated 70–80% of children and adults with ADHD. This is not merely a subjective complaint. It can be objectively measured by examining the timing of evening melatonin release, which is often delayed in individuals with ADHD.

Light, the Biological Clock, and Modern Life

To understand why this problem is becoming more common, we need to talk about light.

Our eyes do more than allow us to see. In addition to rods and cones, we have a third type of receptor: melanopsin receptors. These cells are particularly sensitive to blue light and play a key role in regulating our biological clock.

Morning sunlight is naturally rich in blue light. Exposure to this light early in the day tells the brain that the day has begun and helps synchronize our internal clock with the 24-hour day–night cycle. Evening exposure to blue light has the opposite effect. It suppresses melatonin, delays the feeling of sleepiness, and shifts the biological clock later.

For most of human history, this was not a problem. Traditional incandescent light emitted very little blue light. But modern LED lighting, energy-saving bulbs, tablets, smartphones, and computer screens emit large amounts of blue light. Using these devices in the evening—long after sunset—exposes the brain to light at a biologically unnatural time, delaying sleep onset and contributing to chronic sleep restriction.

Sunlight, Geography, and ADHD

This raises an intriguing question: could daylight exposure itself influence the likelihood of developing ADHD?

Research has shown that regions with higher levels of annual sunlight tend to have lower rates of ADHD. This relationship has now been observed across multiple datasets, including both the United States and Europe (see image below for the USA). The association is strong: sunlight exposure explains a substantial proportion of the variation in ADHD prevalence between regions. The figure below visualizes this association for the US with ADHD prevalence rates (indicated in blue, darker blue is higher rates of ADHD) and sunlight intensity per US state overlaid, use the slider to slide between sunlight intensioty (left) and ADHD prevalence (right).

The interpretation is not that sunlight “cures” ADHD, but that sufficient daylight exposure may protect against chronic circadian disruption—thereby offsetting the effects of evening blue-light exposure.

So Should Children Avoid Screens at Night?

From a biological perspective, there is a balance. Bright light exposure during the day helps advance the biological clock, while excessive blue-light exposure in the evening delays it. More daylight—especially in the morning—can partially counteract the disruptive effects of evening screen use.

Completely banning modern media is neither realistic nor necessary. However, practical steps can make a meaningful difference:

• Use blue-light-filtering modes on phones, tablets, and computers in the evening
• Reduce bright LED lighting at night
• Encourage outdoor activity and daylight exposure during the day, especially in the morning

Perhaps the simplest advice of all is also the most powerful: get more daylight during the day.

Walking or cycling to school, spending breaks outdoors, and yes—letting easily distracted children sit closer to a window—can all help support a healthier biological rhythm.

Rethinking Prevention and Personalization

Taken together, these insights highlight the importance of sleep and circadian timing in attention problems and ADHD.

They also explain why no single treatment works for everyone. Different children may struggle with different underlying sleep or circadian issues (or other non-sleep related causes of ADHD), all of which can manifest as concentration problems. Note, we are not claiming sleep and circadian rhythms explain all of ADHD, however it is an easy to use modifiable risk factor to consider, and for many it could make a clinically meaningful difference. For more sleep questionnaires that can be used in clinical practice also see this page.

This opens the door to a more personalized approach—one that looks beyond the label and asks what a child’s brain and body actually need.

Sometimes, improving attention does not start with medication or therapy, but with something far more fundamental: light, sleep, and timing.

How many hours should my child sleep, and what is an age-appropriate bedtime?

Below find an overview showing the recommended amount of sleep and typical bedtimes for each age group based on the scientific literature. Keep in mind that total sleep duration is the key factor—bedtime may need to be earlier or later depending on how early or late your child has to wake up.

 

Literature

For an overview of scientific studies supporting the above, also see references below:

Arns, M., Heijden, K. B. van der, Arnold, L. E., & Kenemans, J. L. (2013). Geographic Variation in the Prevalence of Attention-Deficit/Hyperactivity Disorder: The Sunny Perspective. Biological Psychiatry, 74(8), 585–590. https://doi.org/10.1016/j.biopsych.2013.02.010

Arns, M., Kooij, J. J. S., & Coogan, A. N. (2021). Review: Identification and Management of Circadian Rhythm Sleep Disorders as a Transdiagnostic Feature in Child and Adolescent Psychiatry. Journal of the American Academy of Child & Adolescent Psychiatry, 60(9), 1085–1095. https://doi.org/10.1016/j.jaac.2020.12.035

Arns, M., Feddema, I., & Kenemans, J. L. (2014). Differential effects of theta/beta and SMR neurofeedback in ADHD on sleep onset latency. Frontiers in Human Neuroscience, 8, 1019. https://doi.org/10.3389/fnhum.2014.01019

Arns, M., Swanson, J. M., & Arnold, L. E. (2018). ADHD Prevalence: Altitude or Sunlight? Better Understanding the Interrelations of Dopamine and the Circadian System. Journal of Attention Disorders, 22(2), 163–166. https://doi.org/10.1177/1087054715599574

Bijlenga, D., Vollebregt, M. A., Kooij, J. J. S., & Arns, M. (2019). The role of the circadian system in the etiology and pathophysiology of ADHD: time to redefine ADHD? ADHD Attention Deficit and Hyperactivity Disorders, 11(1), 5–19. https://doi.org/10.1007/s12402-018-0271-z