Circadian Rhythms and Circadian
[A White Paper
By Apollo Health, Inc].
not the steam engine, is the key-machine of the modern industrial
Lewis Mumford - U.S. social philosopher.
What are circadian rhythms?
Circadian Rhythms are our body's natural cycles
that control appetite, energy, mood, sleep and libido. When our
body is out of sync with nature, we suffer from a Circadian Rhythm
Disorder. Almost all of us, at some time during a year fall out
of balance and suffer from sleep, mood or anxiety disorders. Fortunately,
after decades of research, science has found the way to create circadian
Much of nature is made up of rhythms or cycles.
Common rhythms include the four seasons and the twenty-four hour
rotation of the earth. Like nature, our bodies have rhythms. Some
of the rhythms of body and mind are tied to nature. When working
properly, our bodies respond to nature's cues to create their ideal
For example, when functioning properly, the human
circadian rhythm will respond to the morning light of a new day.
This light will cue the body to produce cortisol, serotonin, and
other hormones and neurotransmitters that get a person awake and
going and cause blood pressure to increase and body temperature
At sunset, the body receives another of nature's
cues and responds to dusk and ultimately the night's darkness. As
the sun goes down the body will produce and secrete the hormone
melatonin, and blood pressure will drop as the body prepares for
and eventually falls off to sleep.
In reality circadian rhythms control the timing,
quantity and quality of the hormones and neurotransmitters the body
produces and eventually secretes. Hormones and neurotransmitters
are the elements that determine how we feel, our sleep patterns,
our appetite, our sex drive and other sleep and mood-related issues.
When functioning properly, our circadian rhythms create circadian
balance. When out of balance, quantity, quality and timing of hormone
and neurotransmitter secretion suffer and our bodies suffer from
a circadian rhythm disorder (CRD).
The Master Clock.
Significant progress is being made in the field
of chronobiology, the formal name for the medical science that studies
circadian rhythms. Researchers have discovered that the human body
is orchestrated by internal biological clocks marching to several
internal rhythms that pace themselves hourly, daily, monthly, seasonally
and even yearly.
Central to the timekeeping mechanism of the body
and mind are Suprachaismatic nuclei or SCN. The SCN is the master
clock the circadian rhythm that controls all other rhythms of the
body. The SCN is actually two clusters of 50,000 neurons, one on
each side of the brain. The SCN sits inside the hypothalamus region
of the brain and works with several time keeping genes.
Together, the SCN and the timekeeping genes make
up the central clock which governs many aspects of physiology and
behavior because they orchestrate the daily rhythms and cycles that
control the ebb and flow of hormones, chemicals and neurotransmitters
that determine wake, sleep, appetite, sex and other key aspects
of our lives. It is vitally important to understand the SCN and
to how to care for it.
The study of circadian rhythms dates back to
the 19th century. However, significant studies and observations
began in earnest in the 1960's. One early pioneer was Curt Paul
Richter, a professor of psychobiology at Johns Hopkins Medical School
whose innovative concepts are the foundation for established concepts
and methods for studying circadian rhythms in humans.
The word circadian is Latin in origin from the
word circa meaning "about" or "approximately"
and dian meaning "day". The term circadian was coined
when Franz Halberg, a scientist at the University of Minnesota,
published a paper in 1959 showing blood count varied according to
a strict rhythm that was about a day. In fact, Halberg discovered
that the rhythms actually went somewhat longer than a twenty-four
The field of chronobiology, the medical discipline
that studies circadian rhythms, has since revealed that the body
undergoes more than just blood count variations. In fact, the body
makes significant changes throughout a day.
Human's Free-running rhythm.
Beginning in 1980, several studies were conducted
to learn more about the human circadian rhythm. These studies included
placing people in an isolated environment without any external cues
or clues as to what time it was. These studies conclude that, if
left alone, healthy humans undergo changes based on an internal
clock that is longer than twenty-four hours. These changes in biological
rhythms can be measured in physical strength, aerobic capacity,
body temperature, blood pressure, mental alertness, production and
secretion of neurotransmitters & hormones, and many other body functions.
No one knows for sure why the cycle is more than
twenty-four hours as opposed to precisely twenty-four hours, nevertheless,
herein lies part of the problem. If the internal circadian clock
of an individual is "free-running", (a state in which
the body is not receiving external signals or cues) it is only a
matter of time before lifestyle realities clash with free-running
circadian time. This clash means hormone and neurotransmitter secretion
becomes confused and will create problems for their health.
Zeitgebers: The Body's
Way of Synchronizing.
In order for to reconcile the difference between
natures exact twenty-four hour cycle and the internal circadian
rhythms we free-run on, nature has given us "zeitgebers",
a German word that means "time givers". As modern lifestyles
demand more flexibility in schedules, man has lost touch with its
most valuable zeitgerber, which is the sun. Modern lifestyles, work
schedules, and indoor living has altered the amount of sunlight
we receive as well as how we set our schedules.
It used to be that people generally woke up at
dawn, worked and spent much of their day outside or near a window,
and at nighttime they read by low levels of light until retiring
to bed. For better or worse, we don't follow that pattern any longer.
Social zeitgebers are important in organizing
the human day. The alarm clock is an important social cue. It wakes
us up and helps us to get on our schedule. Other social zeitgebers
include daily activities such as eating meals together with a family,
watching television, reading the mail or other regimented type of
activities that are habitual in nature.
Out of Synch:
What is circadian rhythm disorder?
A circadian rhythm disorder means your body is
producing hormones, chemicals and neurotransmitters in the wrong
amounts and/or at the wrong time of the day. Circadian rhythms stimulate
the timing and production of countless hormones and chemicals that
affect your sleep and mood. Circadian rhythms permeate practically
every aspect of our lives because they so heavily influence the
chemicals that determine our mood and sleep.
Nature, through its twenty-four hour cycle of
day and night, has provided us with a template or a pattern that
anticipates what we need to be healthy. Nature has obviously anticipated
our needs and when properly synchronized, our bodies respond to
nature's external cues.
The timing of psychological, behavioral, physiological,
and hormonal rhythms with respect to natures external day-night
cycle, clearly imply that temporal order is essential for optimal
health. If this is true, then temporal disorder is a potential recipe
for health and wellness disaster as indicated by a host of clinical
and non-clinical studies. Clearly, many forms of mood and sleep
problems can be traced to a circadian rhythm disturbance.
Because the circadian rhythm influences so much
of how a person feels or sleeps, if a person desires optimal health,
they need to manage their circadian rhythm. If a circadian rhythm
is out of balance, other health aspects will be impacted and out
of balance as well.
What causes circadian
Unfortunately, modern living has dramatically
altered nature's cues. We have developed lifestyle patterns, shelter,
conveniences, and modes of travel that dramatically influence the
cues that drive other mammals. A modern day does not start at the
crack of dawn or end at 8pm.
In a modern day, we get up when the alarm clock
tells us too, work indoors, often in inner cities or interior offices
where there is very little sunlight or the intensity is ineffective
in resetting our circadian clocks. After-work time is spent indoors
at social gatherings or in front of the television or computer often
late into the night. We go to bed late, usually far after we are
tired, and as a result, we are dependant on an alarm clock to get
us up in the morning. Unfortunately, we wake up to man made cues
and our circadian rhythm has not cued our body to secrete the proper
hormones and neurotransmitters resulting in an imbalance.
Circadian Balance is the state we enjoy when
our bodies sleep well, eat right, have lots of energy and feel great;
when in balance we are at our best.
Circadian Light Therapy
Resets and Stabilizes the Circadian Clock - Light is the most
effective way to synchronize the body with the twenty-four hour
day. In the early 1980's two groundbreaking studies were conducted;
one study was conducted at the Albert Einstein College of Medicine
in New York and another at the National Institute of Mental Health.
Both of these studies concluded that specific wavelengths, intensities
and color spectrum of light, (not available in ordinary room lighting)
could reset the circadian clock and create circadian balance. Since
that time, numerous studies have been conducted to understand how
and why light therapy works.
Light, when created in a circadian correct intensity,
wavelength and color spectrum, has been clinically proven to reset
the circadian clock. In addition to resetting the clock, light has
a direct and positive impact by increasing brain serotonin levels.
At the same time circadian light therapy has a depressing affect
on daytime melatonin. Excessive daytime melatonin has also been
linked to depression and sleep disorders.
A key point of the SCN is its location in the
human body. Because the SCN sits in the hypothalmus, it is connected
to the optic nerve. When the eye is exposed to circadian light the
SCN receives this signal and utilizes it as it regulates the circadian
cycle. Unfortunately, most people no longer get enough daylight
to receive the cues that nature intended and as a result there are
millions of Americans suffering from some form of circadian rhythm
The Results of Circadian
New research regarding the human circadian rhythm
and its affect on your body is surfacing on a weekly basis. In fact,
research studies are being done to determine the impact of the circadian
rhythm on hypertension, cancer and a host of other diseases. Over
the last couple of decades there has been significant research and
clinical studies on circadian rhythm as it relates to mood and sleep
Because circadian rhythms control the release
and timing of hormones, circadian rhythm disorder underlies many
mood and sleep disorders. Following are some examples of how circadian
rhythm disorder affects specific kinds of mood and sleep disorders.
Researchers report that depression is closely
tied to circadian rhythm disorders because almost all depression
sufferers have sleep problems and feel worse at a particular time
of day as well as in the winter. When treated with bright light,
these problems improved significantly. Because bright light quickly
corrects the circadian imbalance in depression, patients respond
to light within a week verses months with antidepressant medications.
The fact that depression is circadian related
is further evidenced through a new treatment known as wake therapy.
Researchers believe that depression sufferers have unresponsive
body clocks. Wake therapy awakens the patient several hours early,
which blocks any feedback signals to the body clock when it is most
active. This effect reboots' the body clock, causing it to revert
to an active day cycle. With wake therapy, symptoms of depression
disappear almost immediately. Wake therapy is only necessary for
the first night if used with bright light each successive morning.
This revelation on circadian rhythms and depression
has led researchers to conclude, "These common experiences suggest
that disruptions in biological clocks may be both cause and consequence
of disturbed moods."-- Michael Smolensky, The Body Clock Guide to
No other mood disorder is more closely associated
with circadian rhythm disorder than Seasonal Affective Disorder
or SAD. During the dark fall and winter months, the brain's control
center, the Suprachaismatic Nucleus (SCN) or body clock doesn't
receive the proper stimulus of light. The SCN needs bright light
signals to reset itself each day. When it doesn't receive this signal,
it malfunctions and produces the wrong hormones at the wrong time
Research also shows that without sunlight, the
brain doesn't produce enough serotonin, resulting in the symptoms
of depression . The darker days also signal the brain to overproduce
the hibernation hormone, melatonin. The symptoms diminish as the
days get longer, although many SAD sufferers note brief (1-2 week)
periods of SAD like symptoms in the summer.
Bipolar Disorder is different than major depression
in that it is marked by episodes of euphoria or mania. These episodes
can last for hours, days or even months. In almost all cases of
Bipolar Disorder, depressive and manic episodes are seasonal. In
the Fall and Winter, bipolar sufferers enter a depressive phase,
and require increased intervention. Bipolar sufferers also suffer
from sleep problems and feel worse at a particular time of day.
Because these symptoms reflect a circadian rhythm disorder, doctors
have found success by treating bipolar disorders with bright light.
Premenstrual Syndrome (PMS) is a combination
of physical discomforts and emotional symptoms that happen during
the latter half of the menstrual cycle and usually let up during
the first few days of menstruation. PMS is marked by low levels
of progesterone and serotonin hormones. Researchers believe these
hormones may deplete too quickly, and not allow enough time for
the body to adjust. During this period, women's body clocks also
speed up causing melatonin to be released prematurely and the supply
of serotonin to be cut off. This may account for the increased pain,
irritability and sleep problems.
Chronic illnesses are also at their worst during
PMS. Asthma, depression, diabetes, fibromyalgia, hot flashes, migraines,
acne, rheumatoid arthritis, are all affected by this change in hormone
One interesting study showed that close interaction
between people can affect their biological clock. In the study,
women who lived together, tended to keep regular cycles that coincided
with each other. Their menstrual cycles were often affected as well.
Close women often have their periods at the same time. With many
activities done together, they regularize many biological rhythms,
including those of the hormones that affect the menstrual cycle.
Bright Light helps
PMS - Women's health researchers discovered that PMS is tied
to circadian rhythms. Apparently, the body clock begins to cycle
too quickly during the second half of the menstrual cycle, and may
be a reason why these reproductive hormones deplete too quickly.
Light is known to produce serotonin, the mood hormone lacking in
PMS sufferers. Evening light is also the most effective way to slow
the body clock down to a normal rhythm. When researchers used light
to slow the body clock back down, symptoms of PMS also dissipated.
The discovery that light reduces menstrual problems as well as regulates
cycles, is encouraging, particularly for women who are seeking natural
powerful yet simple and seemingly safe methodology should lead to
exciting progress in our understanding of human reproductive endocrinology.
Daniel Kripke MD, Head of Chronobiology Research, UCSD.
PMDD is a short-term depression, which occurs
during the latter part of the menstrual cycle. PMDD is usually associated
with more severe symptoms of PMS and interferes with the ability
to interact socially. Approximately 5-10% of PMS sufferers also
have PMDD. The difference between PMMD and other disorders is that
its symptoms generally appear the week prior to menstruation.
There is a strong connection between PMDD and
low serotonin. Serotonin acts as a calming hormone. When serotonin
levels are restored, many of the more destructive symptoms of PMDD
disappear, such as pain, anxiety, irritability, anger and food cravings.
The discovery that light regulates serotonin
and melatonin is significant, because these hormones are linked
to PMDD. For example, studies show that women suffering from PMS
and PMMD not only have low levels of serotonin, but that their body
clocks are running too fast. This releases the withdrawal hormone,
melatonin, too early, which depletes serotonin reserves and causes
sleep problems. Using this special light in the evening will slow
the body clock back down and balance natural serotonin levels.
Since light is known to produce serotonin as
well as reset the body clock, researchers at UCSD have had success
using Apollo's Britewave technology in treating women with PMS and
PMDD. Adding light a week before PMS or PMDD occurred, cut symptoms
by at least 50%. This was more effective than drugs alone, but relief
was even greater when light was used in conjunction with medication,
especially for women with severe symptoms. Many women reported complete
relief from light alone.
Prenatal and Postpartum
Prenatal and postpartum depressions are depressive
disorders that occur during or within a year after pregnancy, afflicting
10% of all women. Prenatal and postpartum depressions are among
the most serious mood disorders for women because they impact the
health of the fetus and newborn. An expectant mother will not take
as good care of herself, which may harm the fetus. Studies also
show that depressed mothers don't care for their babies as well
as other mothers. They talk less, show less affection and don't'
respond as well. As a result, their babies have more problems socially;
they withdraw, and are less animated than other babies. Commenting
on the long-term consequences,
÷Children of depressed
mothers are at increased risk for anxiety disorders in childhood,
major depression in adolescence, and alcohol dependence in early
adulthood. Furthermore, depressed offspring of depressed parents
have a longer duration of episodes, more impairment, more medical
problems and receive less mental health treatment. In addition to
having more serious and recurrent depression, they are more socially
and vocationally impaired. Thus, to reverse these adverse consequences
of maternal depression, treatments need to be instituted early in
the course of the illness.
Why expectant and
new mothers become depressed - Pregnancy and delivery causes
hormone levels in some women to be too low. During pregnancy, the
body clock releases hormones that increase the body's ability to
deal with the added stress of having a baby. These hormones take
their toll though, by depleting reserves of serotonin, the hormone
associated with wellness and mood. During the third trimester and
just after birth, serotonin levels are as low as those found in
people with major depression. This is why over 70% of new mothers
experience the blues,' and 10% suffer from depressive illnesses.
Pregnancy and postpartum depressions affect the
body clock Researchers have also noted a strong connection between
circadian rhythms and pregnancy related depressions. Symptoms are
generally worse in the morning time, and the sleep problems are
a result of disrupted circadian rhythms. Since light is known to
produce serotonin as well as reset the body clock, researchers at
Yale and UCSD have had success using Apollo's BRITEWAVE¾ technology
in treating women with pregnancy related depressions. In this case,
the specialized light is used in the morning time. News that morning
bright light is helpful is important because anti-depressant medication
is undesirable during pregnancy and nursing.
Because the circadian rhythm controls the sleep/wake
cycle, circadian rhythm disorder often results in insomnia. If there
is a pattern to the sleep disturbance, i.e., one consistently wakes
up or falls asleep at the wrong time, or if he/she cannot get to
sleep at certain times, it is most likely that his/her circadian
rhythm is malfunctioning.
The American Academy of Sleep Medicine (AASM)
estimates that 25% of all sleep problems are directly related to
circadian sleep disorders and several other sleep problems are either
caused by or contribute to circadian rhythm disorders. These sleep
disorders include late night and early morning, insomnia, interrupted
sleep patterns, free-cycling sleep disturbances and irregular sleep
disorders. (For specific information on all circadian related sleep
disorders, visit the sleep section on this webpage.) The two most
common sleep problemsLate night and early morning insomnia are
Late Night Insomnia
- The majority of people with sleep problems experience difficulty
being able to fall asleep. They may only experience a few hours
of sleep each night, and feel worse in the morning time. In this
case, the body clock is running slower than a normal circadian rhythm
(24 hour period). The clinical term for late night insomnia is Delayed
Circadian Rhythm Disorder or DCR. DCR sufferers' body clock doesn't
'wake up' until later in the morning or day. They have difficulty
getting started in the morning, may feel a bit groggy or down during
part of the day, and may experience a second wind later in the evening.
Those with DCR are often referred to as night owls, and find it
easier to stay up late at night.
With DCR, the daily cycle, or circadian rhythm
is running slow, and the pineal gland releases the nighttime hormone
melatonin too late, causing sleep to occur later. In the morning,
the body clock is still producing the nighttime hormones. This is
why it may take several hours to feel active and energetic. Because
DCR sufferers don't receive the proper amount of sleep, energy,
alertness and ability to function may also be diminished.
Because DCR is the result of a slower circadian
rhythm, bright morning light is the most successful means to speed
the body clock up and restore circadian rhythms to their normal
function. Because DCR disorders vary with individuals, the treatment
schedule needs to be adapted accordingly. Apollo provides an effective
assessment tool on its website for determining the proper treatment
schedule and guidelines.
Early Morning Insomnia
- As people age, they tend to have difficulty staying asleep, and
usually awaken hours before dawn. Those with early morning insomnia
generally tire easily in the afternoon or evening and have little
difficulty falling asleep. The clinical term for this disorder is
Advanced Circadian Rhythm Disorder or ACR. ACR happens when the
body clock is running faster than a normal 24-hour period. Because
the body clock is running too fast, ACR sufferers tend to run out
of energy before the 'day' or 24 hour period is through. ACR also
tends to compress the sleep portion of the daily cycle, causing
ACR sufferers often sleep less than 8 hours per night.
Because the circadian rhythm is running fast,
the pineal gland releases the nighttime hormone melatonin prematurely,
causing one to feel tired earlier in the evening. Since melatonin
is released prematurely, the body clock can't sustain a complete
sleep cycle, causing early insomnia.
Bright evening light has been shown to be the
most effective treatment for ACR. Evening light slows the body clock
down to a normal rhythm. This delays the onset of melatonin and
sleep, allowing the person to sleep longer and have more energy
in the late afternoon and evening.
to other sleep disorders.
Circadian Rhythm Disorders keep our bodies from
enjoying a complete or rejuvenating sleep. Because CRD's disrupt
the sleep pattern, they may contribute to narcolepsy, sleep apnea,
snoring, etc. Most people find these symptoms diminish when their
circadian rhythms are working properly
that show a circadian Pattern.
Jet lag is the result of one's body clock being
out of synch with a new time zone. The symptoms of jet lag are similar
to depression, and will persist until the body clock can respond
to the new time. Without intervention, this process takes one to
two weeks, depending on the distance traveled. Jet lag is easily
avoided by using timed bright light to speed up the body clock's
adaptation to the new time.
Shift work almost always causes a circadian rhythm
disruption, where a person's internal body clock is at odds with
the shift schedule. Shift work problems are well documented and
range from perfomance issues to accidents and other health problems.
Recent evidence shows that shift work may contribute to cancer because
working at night in well lit enviornments suppresses melatonin,
which acts as a powerful anti oxident. Additionally, proper circadian
signaling causes cells to die, and shift workers may not be receiving
these needed signals. As a result, mutated or deformed cells continue
to grow when they otherwise would be destroyed.
Shift workers can easily adapt their body clocks
to work within the shift schedule's requirements by using a light
therapy protocol. Using this protocol will increase work performance,
improve sleep and off-shift scheduling problems, as well as decrease
health and cancer related risks.
Chronic Fatigue Syndrome.
The Centers for Disease Control and Prevention
(CDC) has documented that a circadian pattern exists in Chronic
Fatigue Syndrome (CFS). Pain, fatigue, mood, social activity, energy,
sleep and weight worsened significantly in the Winter. In addition,
about half of CFS sufferers also have major depression in the Winter.
Because circadian rhythms affect CFS, researchers have found success
treating with light therapy, and have commented that, ÷Light therapy
may provide patients with CFS an effective treatment alternative
or adjunct to antidepressant drugs.
See appendix I ÷Sizing
Smolensky, M., L.
Lamberg. The Body Clock Guide to Better Health. Henry Holt and
Smolensky, M., L.
Lamberg. The Body Clock Guide to Better Health. Henry Holt and Company,
Hastings, M. H.
The Brain, Circadian Rhythms, and Clock Genes. BMJ 317:19-26. 1998
Halberg F. Physiologic
24-hour periodicity: General and procedural with reference to the
adrenal cycle. Z. Vitamin, Hormon-u. Fermentforsch. 10:225-296.
Czeisler, C.A., J.F.
Duffy, T.L. Shanahan, E.N. Brown, J.F. Mitchell, D.W. Rimmer, J.M.
Ronda, E.J. Silva, J.A. Allan, J.S. Emens, D. Derk-Jan, R.E. Kronauer.
Stability, precision, and newar 24-hour period of the human circadian
pacemaker. Science 284:2177-2181.
Biological Rhythms in Mood Disorders. 2000. University of Switzerland
; Kripke, DF et al.
Light Treatment for Nonseasonal Depression: Speed, Efficacy, and
Combin ed Treatment, The Journal of Affective Disorders. 1998 49
Loving, RT et al.
Bright Light Augments Antidepressant Effects of Medication and Wake
Therapy. Depression And Anxiety. 2002: 16; 1-3
Lambert, GW et al.
Effect of sunlight and season on serotonin turnover in the brain.
The Lancet 2002; 360:1840-42
Lam, R et al.
Canadian Consensus Guidelines for the Treatment of SAD. 1999; Clinical
and Academic Pubishing. 33-35
Parry, et al.
Blunted Phase-Shift Responses to Morning Bright Light in Premenstrual
Dysphoric Disorder. Journal of Biol Rhythms. 12: 5, October 1997:
Parry, B et al.
Can Critically timed sleep deprivation be useful in pregnancy and
postpartum depressions? Journal of Affective Disorders. 60 (2000)
Terman M, et al.
Light treatment for sleep disorders: consensus report. IV. Sleep
phase and duration disturbances. Journal of Biological Rhythms.
Terman M, et al.
Chronic fatigue syndrome and seasonal affective disorder: comorbidity,
diagnostic overlap, and implications for treatment. American Journal
of Medicine. 1998: Sep 28;105(3A):115S-124S
Espiritu, RC et al.
Low illumination by San Diego adults: association with atypical
depressive symptoms. Biol.Psychiatry. 1994;35:403-407; Kripke, DF
et al. Adult illumination exposures and some correlations with symptoms.
in Hiroshige T, Honma K (eds): Evolution of Circadian Clock. Sapporo,
Hokkaido University Press; 1994:349-360.
Czeisler, C.C., et
al. Entrainment of Human Circadian Rhythms by Light-dark Cycles:
A Reassessment. Photochemistry and Photobiology. 1981; 34:239-247.
Lewy, A., Light
Supresses Melatonin Secretion in Humans. Science. 1980;210:1267-1269
Lambert, C.W., Reid,
C., Kaye, D.M., Jennings, G.L., Esler, M.D., Effect of Sunlight
and Season on Serotonin Turnover in the Brain. The Lancet 360:1840-1842.
Brainard, G.C., Hanifin,
J.P., Greeson, J.M., Byrne, B., Glickman, G., Gerner, E., Rollag,
M.D., Action Spectrum for Melatonin Regulation in Humans: Evidence
for a Novel Circadian Photoreceptor. The Journal of Neurosckience,
Varma A, Kaul RK,
Varma P, Kalra V, Malhotra V. The effect of antidepressants
on serum melatonin levels in endogenous depression. J Assoc Physicians
India, 50:1262-5. 2002
This information is used by kind permission of
Apollo Healthcare of Utah.