Some people will go to bed at a certain time of night, say 10 or 11 pm, and find it takes them a really long time to fall asleep. However, once they fall asleep—at 1 or 2 in the morning—they sleep completely through the night and get a full 8 hours.
Yet, they visit their doctor and complain of insomnia because it takes so long for them to fall asleep.
If this describes you, it might be helpful to know that there is a name for this kind of sleep pattern: delayed sleep phase syndrome.
A delay in sleep phasing of at least 2 hours later than what is considered "normal" for others, followed by a complete night of healthy sleep, defines this unusual sleep-wake pattern.
To understand why it happens and whether it could be a problem, you first have to understand a little bit about the circadian system.
What are sleep phases?
The circadian system operates on a 24-hour clock that is more or less biologically synchronized, or entrained, to the earth's light-dark cycles. This is why it's considered normal to sleep when it's dark and to be most active while it's light.
These are not happenstance behaviors, but rhythms built inside our brains and bodies which use light exposure to ensure all of our systems are working in balance and tandem with one another.
Sleep phases are based on a few specifics.
When the sun goes down, light perception through the eye signals to the brain that evening is coming so that it will signal the pineal gland to release melatonin, a substance which encourages sleep.
Certain activities during the day also impact sleep phases. Evening meals create a shift in digestive rhythms (peristalsis) which coordinates with melatonin release for the purpose of encouraging sleep.
Also, enough wake time during the day leads to an increase in the brain and body's need for sleep. At night fall, our "sleep drive" begins to overtake our "wakefulness" drive.
These specific factors help to phase sleep in (as well as phase wakefulness out). For most human beings, sleepiness begins to take place after dinnertime, and for the most part, the majority of us are in bed well before midnight.
However, for some, midnight is too early a bedtime (if you have teenagers, you might have noticed this about them). A typical bedtime for them is well after midnight. It's not that they have insomnia. It's the way that their brain and body rhythms have shifted, from wakefulness to sleep... slightly off of the established pattern.
The result is delayed sleep phase syndrome, or DSPS (or, formally, Delayed Sleep-Wake Phase Disorder, according to the International Classification of Sleep Disorders, 3rd Ed.)
What is delayed sleep phase syndrome (DSPS)?
If you find that, even with proper preparation for bedtime at 10 or 11 pm, you still routinely do not fall asleep until well after midnight, it could be that your personal circadian clock is phase delayed.
Essentially, your sleep phase runs later than what is considered "normal" for society. This means you end up going to bed "late" for somebody else, but "right on time" for your particular rhythms.
If you can go to bed at 2 am and sleep until 10 am, wonderful! You still get your full 8 hours of sleep.
However, most people have to rise at earlier times to satisfy the scheduling demands of jobs, family, and/or school. Many people with DSPS still must rise at 6 am to meet these obligations, and that means they are getting roughly half the sleep their body needs to function normally. So they become sleep deprived, find themselves drowsy and making mistakes during the day, and nodding off or taking naps to make up for lost sleep.
This doesn't point to insomnia. About 10 percent of people complaining of insomnia at the beginning of the night actually have DSPS.
It is the most common of all the circadian rhythm sleep disorders. It's estimated that as much as 16 percent of the general population suffers from delayed phase shifting.
It usually starts with the normal delay in phase shifting that is part of adolescence, which occurs while final brain development takes place. Most grow out of this pattern by adulthood, but some remain shifted to later hours.
DSPS and "night owls"
For some people, a later bedtime is more a matter of preference. They don't considered themselves "morning people" but "night owls."
These people make the choice to stay up and typically have the opportunity to sleep in. They may naturally work later hours or find they are more energized later in the day.
For others with an early-morning schedule, having DSPS takes away this preference. They have circadian rhythms that are set for a later bedtime, but their lifestyle cannot accommodate their daytime schedule demands. Try as they might, they cannot fall asleep earlier than usual and they definitely cannot awaken at the crack of dawn. They are "night owls," but not by choice.
While it's normal for everyone to stay up late on occasion, most people return to their established routine. People with DSPS cannot. They are wired for "eveningness," versus those earlybirds who are wired for "morningness."
The main challenge with DSPS comes in morning awakening. People with DSPS, who must keep morning hours that are "early" for them, may struggle to get out of bed even after multiple alarms have gone off and family members have taken great lengths to wake them up.
Delayed sleep phase syndrome symptoms
DSPS can wreak havoc on a person's life. Here are the main signs:
Inability to fall asleep at a "decent" hour, followed by an inability to wake up at a "decent" hour.
Excessive daytime sleepiness due to sleep deprivation; most people with DSPS rarely, if ever, get their full 8 hours of sleep at night because of morning schedules.
Depression-like symptoms; as many as half of all people with DSPS suffer from depression.
Problems with attention and focus during the day.
Dependence on caffeine or other stimulants during the day and sedatives or alcohol at night.
Notable increase in accidents at work, at home, in the car, and general clumsiness.
It's important to note: DSPS occurs in the absence of other sleep problems. People with DSPS may sleep very well otherwise, they are just sleeping "off schedule."
If they are allowed to sleep their full night on this shifted schedule, they awaken without help, feeling refreshed, and energized all day.
Delayed sleep phase syndrome causes
Mostly, DSPS is a "body clock problem" with few clearly understood biological causes. Here are some risk factors:
Genetics. DSPS can run in families; 40 percent of people with delayed sleep phase may have inherited this trait from their parents.
Age. It's actually normal for teenagers to be delayed in their sleep phasing, even without computers, homework, social circles, the Internet, or blue spectrum light to keep them awake at night.
Lack of exposure to morning sunlight.
Too much exposure to bright light after sundown.
How is delayed sleep phase syndrome different from insomnia?
It's important to differentiate between a true case of insomnia and a true case of DSPS because treatments for either sleep disorder are quite different from one another.
Insomnia disorder is typically treated with behavioral therapies or a combination of these with hypnotic medications. Treatment of underlying medical or mental health disorders can also bring relief to insomniacs.
However, in the case of DSPS, there are a number of complex approaches to resetting one's rhythms to adapt to a schedule that more suits a person's lifestyle, but rarely do they involve drugs. Instead, they require some close work with a sleep specialist over a period of time to reestablish circadian synchronicity.
When does DSPS become a sleep disorder?
It depends entirely upon the individual.
For someone who doesn't need to awaken early on a daily basis for a job, school, or family commitments, a DSPS sleeping schedule is only inconvenient or problematic in the rare circumstance where they need to rise earlier than usual (to catch a flight or to make a doctor's appointment, for instance).
However, a person who must commute to a job that starts at 9 am (or earlier) can quickly default to a life cursed with sleep deprivation because DSPS is not a sustainable sleeping pattern for them. This holds true for students with morning classes, mothers who need to get their young children off to school, and anybody else who must adhere to an early morning routine out of obligation.
Night after night of short sleep for these people results in sleep debt and all the health consequences that come with it.
People who struggle with the activities of daily living because of DSPS are no longer diagnosed as having DSPS but DSPD, which stands for Delayed Sleep Phase Disorder.
People with DSPD not only have to manage the side effects of sleep deprivation, but they also struggle with maintaining healthy relationships with others because of their odd schedules. The inconvenience of sleeping in also shortens their days, making it difficult to run errands, do the shopping, or make appointments.
Two common approaches to treating DSPD include the use of the supplement, melatonin, and applications of phototherapy.
Though this nutritional supplement is easily purchased from a drugstore and generally recognized as safe, it is not an FDA-regulated substance and researchers are still not completely clear on how it works on the brain.
Recent studies show melatonin inside the body has multiple roles in regulating other body processes, so more research is needed to understand this complex hormone.
One thing scientists do know is this: the timing and dosage of melatonin are both critical for its success in treating DSPD. While it has been shown to be effective in advancing sleep phases to a more "normal" schedule, its inappropriate use could actually worsen sleep-wake cycles.
Melatonin also has side effects, such as:
potentially dangerous interactions with certain maintenance medications such as blood thinners, insulin, birth control pills, and immunosuppressant drugs
About light therapy
Also called phototherapy, this involves intentional exposure to specific doses of bright light in the early morning, and avoidance of bright light at night.
This approach can help someone with DSPD to "reset" their circadian rhythms to a more livable schedule.
Sunlight during the day is an easy source of bright natural light, but for those who live in cloudy climates or dark winters, an indoor therapeutic light—also known as a "happy light" for the way it can also help elevate mood—may be more convenient.
As with the use of melatonin, use of phototherapy must be supervised by a sleep specialist to ensure light interventions follow a strict protocol. Incorrect use of light therapy can actually worsen your sleep phase problems.
Also, light therapy is not beneficial for those with other health problems, such as bipolar disorder; inappropriate exposure to bright light for these individuals can lead to manic episodes.
Ultimately, if you suspect you have DSPS but you can live with it, then it may not be a problem for you. But if a later sleep schedule has turned your life upside down, you need to be proactive about solving the problem with the help of a sleep specialist.
Sleep deprivation, arguably the worst side effect of untreated DSPD, is considered by the Centers for Disease Control to be the biggest chronic health problem in the US. It comes with a long list of adverse results (depression, anxiety, diabetes, a compromised immune system, obesity, fibromyalgia, and cancer). Ignore the symptoms of DSPS at your own peril.
American Academy of Sleep Medicine
American Sleep Association
Centers for Disease Control
Circadian Sleep Disorders Network
International Classification of Sleep Disorders (3rd Ed.)
The New York Times
Sleep Medicine Clinics