What causes delayed sleep phase disorder?
Key Findings
Delayed Sleep Phase Syndrome occurs when a person’s internal body clock runs several hours later than the typical day. This delay is driven by a combination of genetics, differences in circadian rhythm timing, late melatonin release, and lifestyle factors such as evening screen use and limited morning light. Psychological influences like ADHD, anxiety, and stress can reinforce the delay, while modern environments filled with artificial light make it harder for the brain to recognise nighttime.
Delayed Sleep Phase Syndrome Causes
Delayed Sleep Phase Syndrome, often called DSPS, is a circadian rhythm disorder in which a person’s internal body clock naturally runs several hours later than what society typically expects.
Someone with DSPS may not feel sleepy until the early morning hours and often struggles to wake at a conventional time, even with alarms or strict schedules. This is not a matter of laziness or poor discipline. DSPS reflects a biological shift in the timing of the sleep-wake cycle that can be deeply rooted and difficult to change.
Understanding the causes of DSPS can help people recognise that the condition is real, manageable, and often influenced by factors outside of their control.
The Internal Clock and Why It Shifts Late
At the centre of DSPS lies the circadian rhythm, a roughly 24-hour internal timing system controlled by a small part of the brain called the suprachiasmatic nucleus. This internal clock regulates when we feel awake, when melatonin rises, and when the brain begins preparing for sleep.
In people with DSPS, the internal clock is delayed. They do not feel a natural wave of sleepiness until hours after most people have already gone to bed.
This delay can reach two, three, or even four hours. Interestingly, when people with DSPS are allowed to follow their natural schedule, they usually sleep deeply and wake feeling rested. The problem arises only when external obligations conflict with their biological timing.
This delayed rhythm often begins during adolescence, a time when circadian physiology naturally shifts later. For many, it returns to a more typical pattern in adulthood. For others, especially those with strong genetic or environmental influences, the delay remains.
Genetics and Biological Influence
Research suggests a strong genetic component in DSPS. People with a family history of night owl behaviour or circadian rhythm disorders are significantly more likely to develop the condition themselves.
Certain gene variants alter how sensitive the body is to light, how quickly melatonin rises in the evening, or how long the circadian cycle lasts.
For some individuals, their biological day is naturally slightly longer than 24 hours, meaning their sleep time drifts later each day unless anchored by strong environmental cues.
This genetic influence helps explain why simply “going to bed early” does not work. If melatonin is not yet rising, the body does not initiate the physiological process of sleep, no matter how tired you want to feel.
Light Exposure and Modern Lifestyles
Light is the most powerful external regulator of circadian rhythm. Morning sunlight signals the body to wake, while darkness triggers melatonin release and helps prepare the brain for sleep. In DSPS, there is often a mismatch between light exposure and internal timing.
Many people with DSPS spend most mornings indoors, missing the bright natural light needed to reset the clock. At night, artificial lighting, screens, and bright overhead bulbs continue to signal wakefulness long after sunset. This combination delays melatonin release and reinforces the late sleep pattern.
Technology plays a major role as well. Phones, laptops, and televisions all emit blue light that suppresses melatonin. When used late into the night, these devices can push the internal clock even further out of alignment.
Psychological and Neurological Factors
Certain psychological and neurological conditions are strongly linked with delayed sleep timing.
People with ADHD frequently experience DSPS due to differences in dopamine regulation, heightened nighttime alertness, and patterns of hyperfocus that continue well past midnight.
Anxiety can also delay sleep onset by increasing mental activity at a time when the brain should be settling. Depression may shift the circadian rhythm later and reduce the strength of internal signals that promote sleep.
Stress is another major factor. High or prolonged stress elevates cortisol, a hormone that is normally highest in the morning and lowest at night. When cortisol stays high in the evening, the brain struggles to enter a restful state, reinforcing a later sleep pattern.
Lifestyle Behaviours That Reinforce Delay
Although DSPS is not caused by behaviour alone, certain habits can intensify or prolong the delay.
Late-night studying, gaming, or working keeps the brain active at a time when it should be winding down. Irregular sleep schedules, especially staying up much later on weekends, weaken circadian cues and make earlier bedtimes harder.
Lack of morning structure also plays a role. When meals, movement, and daylight exposure do not occur consistently, the internal clock receives fewer signals about when the day begins.
These behaviours are not the root cause of DSPS, but they can make the shift more pronounced.
Environmental and Social Pressures
Modern life often clashes with biological timing. People living in noisy environments or shared households may struggle to create calming bedtime routines.
Students and professionals who work late into the evening can unintentionally train their body to expect wakefulness at night. Shift work, frequent travel, and inconsistent schedules further weaken the circadian rhythm’s alignment.
These external pressures help explain why DSPS is more common in teenagers, young adults, and individuals in demanding academic or creative fields.
Final Thoughts: DSPD Causes
Delayed Sleep Phase Syndrome is the result of a complex interaction between genetics, circadian biology, lifestyle habits, and environmental influences.
It is not simply a preference for staying up late but a genuine shift in internal timing that can create significant challenges in daily life. With the right understanding and strategies, many people can improve their sleep timing or learn to work more effectively with their natural rhythm.
Article FAQ
Can you cure Delayed Sleep Phase Syndrome?
DSPS cannot always be completely cured, but it can often be managed very effectively. Many people improve their sleep timing through a combination of morning light exposure, consistent routines, reduced evening screen use, melatonin taken under professional guidance, and behavioural strategies such as gradually shifting bedtime earlier. In some cases, especially when DSPS has strong genetic roots, the goal is to manage the condition rather than eliminate it. With the right approach, most people achieve a workable and more predictable sleep schedule.
How is DSPS diagnosed?
Diagnosis typically involves a sleep specialist reviewing your sleep history, preferred bedtime, wake times, and any difficulties functioning within a conventional schedule. You may be asked to keep a sleep diary or wear an actigraphy device, which tracks sleep patterns over several days. Diagnosis focuses on identifying a consistent delay in the natural sleep window, rather than occasional late nights or irregular routines.
How common is Delayed Sleep Phase Syndrome?
DSPS is more common than many people realise. It affects an estimated one to five percent of adults, but the rates are significantly higher in teenagers and young adults. Because the condition is often mistaken for staying up late by choice, many cases go undiagnosed. DSPS also appears more frequently in people with ADHD, mood disorders, or a family history of circadian rhythm differences.
What causes Delayed Sleep Phase Syndrome?
DSPS develops from a combination of factors, including genetics, delayed melatonin release, reduced morning light sensitivity, evening screen exposure, and modern lifestyle patterns that favour late-night activity. Psychological factors such as stress, anxiety, and neurodevelopmental conditions can reinforce the delay. The underlying issue is a naturally shifted internal clock rather than a lack of discipline or motivation.
Is DSPS the same as being a night owl?
Not exactly. Many night owls simply prefer evenings but can still fall asleep earlier when needed. DSPS is different because the shift in timing is biological and persistent. People with DSPS often struggle to fall asleep early even when exhausted and typically feel their best only when allowed to sleep and wake according to their internal timing. It is a medical condition, not a preference.
Can DSPS get worse over time?
It can, especially when sleep schedules become irregular or when evening screen use, stress, or inconsistent morning routines strengthen the delay. However, with structured habits and attention to circadian cues, DSPS often becomes easier to manage. For some people, symptoms naturally lessen with age as the internal clock becomes more stable.
