Sleep-disordered breathing linked with depression

Snorting, gasping or stopping breathing while asleep has been associated with nearly all depression symptoms. The Centers for Disease Control and Prevention (CDC) surveyed 9,714 Americans for a new study appearing in the April issue of SLEEP. The CDC determined that the likelihood of depression increased with the frequency of sleep-disordered breathing.

Symptoms reported included feelings of hopelessness and feeling like a failure. The association was made regardless of factors like weight, age, sex or race. The CDC study is the first nationally representative sampling to look at obstructive sleep apnea (OSA) and depression. Similar links have been made in previous studies, but in samples that were much smaller and more specific.

The study’s authors suggested that physicians screen for depression in the presence of sleep-disordered breathing, or vice versa. The said such screenings could help reduce the high incidence and under-diagnosis of both of these disorders.

Read more blog posts about sleep and depression. Or learn more about insomnia, or take a short quiz to test how well you sleep.

Clock Gene Levels Linked to Insomnia and Depression

Scientists are learning why insomnia and depression are so closely interconnected. Sleep disturbances, especially early morning awakenings, are a common symptom of depression. An Ohio State University study suggests that these symptoms are related to an over-active body clock.

The so-called Clock gene helps regulate the body’s circadian rhythms. Molecular-level disturbances in the Clock gene may disrupt the 24-hour body clock, causing sleep problems.

The study compared the blood samples of people with a history of depression to those who had never been clinically depressed. The study included 60 participants; 25 spent at least five hours per week caring for a family member with dementia.

Blood analysis shows people with a history of depression had higher levels of the Clock gene. The relationship held true after statistical adjustments for age and lifestyle factors such as substance use, exercise, medical conditions and caregiving status.

Researchers also analyzed three other circadian genes, but found no statistically significant differences in gene levels between depressed and non-depressed subjects.

The authors of the study caution that the findings demonstrate there is a link, but causal direction remains unclear. In other words, further research is needed to determine whether depression causes the clock gene to be elevated, or vice versa.

Researchers explain their findings are simply a snapshot of how gene activity differs between people with and without depression.

Several other studies have attempted to explain the link between insomnia and depression.

A study published in the September 2010 issue of SLEEP suggests sleep deprivation causes depression in young adults. Every hour of sleep lost significantly raises the risk of emotional distress, a combination of high levels of depressive and anxious symptoms.

Another study presented at SLEEP 2010 in San Antonio reported similar findings, but for teenagers. Students who reported problems with daytime sleepiness were three times more likely to have depression compared to their peers.

In any case, the treatment options for depression and insomnia often overlap. While medication can help in the short term, cognitive-behavioral therapy is the best approach for lasting results. Conquering depression and insomnia takes a lot of work, but your health and happiness are worth the effort.

Many Non-Depressed Insomniacs Have Suicidal Desires

Insomniacs have no shortage of alone time. Countless overnight hours are spent pondering, obsessing and agonizing over the inability to sleep and the stressful things in your life. This endless introspection may give rise to momentary suicidal desires.

The two-way relationship between sleeplessness and mental health disturbances is well documented at this point. Insomnia is both a symptom and a risk-factor for depression. In fact the DSM-IV lists disturbed sleep patterns as one of the nine main criteria for the diagnosis of major depressive disorder.

You don’t have to be depressed have suicidal thoughts with insomnia, a new study published in Sleep Medicine reports. The article concludes insomnia can predict suicidal desires, with or without diagnosable depression.

The clinical study involved 60 middle-aged patients with depression and insomnia. The subjects were prescribed the anti-depressant Prozac along with the sleeping medication Lunesta or a placebo. Over the course of the 8-week study, the patients were repeatedly assessed for insomnia, suicide ideation and depression.

Statistical analysis shows, although depression severity was directly linked to intensity of suicidal thinking, a similar relationship also holds true for severity of insomnia. Insomnia patients who were no longer depressed still had suicidal thoughts.

These findings further flesh out a disturbing revelation reported this month in the journal SLEEP. Middle-aged men with long-term insomnia are likely to die over a 14 year period. The large-scale, long-term study did not investigate the exact causes of the deaths, but it’s not too much of a stretch that some were suicides.

Like pushing through depression, conquering long-term insomnia can take hard work and dedication. Leading a longer and happier life is clearly worth the effort of working with a clinical sleep specialist to change your nighttime routine and eliminate harmful beliefs that prevent sleep.

Depression, Mental Distress May Start with Short Sleep

A variety of everyday problems can be maddeningly difficult on little sleep. Minor conflicts may cause a sleep-deprived person to feel frustration, anger or even sadness. Slight disruptions become emotional eruptions in the absence of restful sleep.

For teenagers and young adults who already grapple with heightened hormones, a string of sleepless nights can turn them into walking time-bombs. Mental illness is a real risk for many people less than 24 years of age who don’t get enough sleep, according to a new study in the September issue of the journal SLEEP.

The study reports that every hour of sleep loss significantly raises the risk of emotional distress, a combination of high levels of depressive and anxious symptoms. The risk is most relevant for people with pre-existing mental health issues or a history of depression.

Young adults who otherwise have no mental health history can develop mental distress by severely limiting sleep over a long period of time. The study found people with no psychological distress who slept five hours or less are three times more likely to be distressed a year later.

The study design involved 20,000 Australians aged 17 to 24. Each participant completed a sleep diary by listing the amount of hours slept per night over the course of a month. Subjects also answered the Kessler Psychological Distress Scale (K10), a mental assessment that includes questions about feeling tired, nervous, hopeless, restless, depressed, sad and worthless.

A randomly selected group consisting of about 10 percent of the participants completed a follow-up survey about a year later. Approximately 1 in 5 young adults who responded slept fewer than seven hours per night. Less than two percent were extremely short sleepers with less than five hours per night.

Mental health and psychological stress is a serious concern for young adults of any nation. The U.S. government estimates nearly 1 in 5 people between the ages of 18 and 25 years of age experienced serious psychological distress in the past year.

There’s been much discussion this early September about the risks related to insomnia and short sleep duration. A widely-reported study linked long-term insomnia to death for middle age males. Another study published in the same journal focused on teenage sleep patterns and suggested a relationship between sleep length and obesity. It concluded teenagers who sleep less than eight hours a night usually have unhealthier diets, consisting of fatty foods and frequent snacks.

Teenagers and young adults need more sleep than their parents or older siblings yet many in the age group are inclined to stay up late due to natural night-owl tendencies. High levels of stress and numerous distractions such as cell phones and video games also keep young adults from getting to bed at a decent hour.

The good news is after high-school, many have a more flexible schedule that can suit their sleep needs. This is especially the case for college students, who can avoid early morning classes if they wish. There’s no mental harm in sleeping too much. The study reports participants who reported sleep durations of more than nine hours showed no heightened mental distress.

Image by Andi Jetaime

Sleep Drug during Depression Treatment can Solve Insomnia Symptoms

Insomnia and depression are often closely related. The relationship can go both ways: depression can cause insomnia, and insomnia can lead to depression.

Depression drugs are the front-line treatment for most patients, but as the bleakness of depression goes away the sleeplessness often stays.

A team of researchers say the insomnia can be easily solved by altering patients’ prescriptions. They found that pairing the hypnotic sleeping pill Lunesta with serotonin reuptake inhibitors (SSRI) may be the ideal approach for depression with insomnia.

The study involved 60 patients diagnosed with depression and insomnia. After one week of taking Prozac, the subjects began combining the drug with Lunesta or a placebo.

Patients who took the sleeping drugs reported a higher health-related quality of life. Depression improved and the patients had less difficulty sleeping.


The AASM reports that insomnia can occur in 85 percent of people with a major depressive episode. Frequent awakenings during the night are typical; waking up early in the morning and being unable to go back to sleep also is common.

Often the insomnia complaint is among the earliest symptoms to appear in a person with a mental health disorder. People often attribute their mental symptoms to poor sleep.

Photo by Max Talbot-Minkin

Tired teenagers prone to depression

High school students who don’t get the recommended nine hours of sleep per night are three times as likely to have depression, according to a research abstract to be shown Wednesday at SLEEP 2010 in San Antonio.

The study found sleep deprivation is widespread among teens in the U.S. 52 percent of seniors at a public high school in New Jersey reported excessive daytime sleepiness.

Students averaged only 6.1 hours of sleep on school nights and 8.2 hours on weekends. The American Academy of Sleep Medicine reports students need more than nine hours of sleep to stay alert during the day.

More than 250 high school seniors participated in a cross-sectional survey. Excessive daytime sleepiness was defined as a score of 10 or higher on the Epworth Sleepiness Scale. Mood was evaluated with a validated depression scale.

A study published earlier this year in the journal SLEEP further supports these findings. The article reported adolescents who went to bed at midnight or later were 24 more likely to have depression compared to teens with parental set bedtimes earlier than 10 p.m.

Some experts advocate pushing forward school start times to give teens more time to sleep. The author of the study suggests public high schools should regularly screen for sleep deprivation and depression.

Pregnancy, Sleep & Postpartum Mood

A new study examined the relationship between disrupted sleep and postpartum mood in mothers. The results were published today in the journal Sleep.

The study from Australia involved 44 healthy women. They all had a low risk for postpartum depression. Their ages ranged from 18 to 41 years. Sleep was measured by actigraphy for seven days during the third trimester and seven days after giving birth.

Results show that sleep deteriorated after delivery. Total sleep time at night fell from 428 minutes in the third trimester to 373 minutes after delivery. Daily nap time increased from 32 minutes to 101 minutes.

Forty-six percent of women had some deterioration of mood after delivery. But the link between objective sleep measures and mood was weak. Variables related to the subjective perception of sleep were stronger predictors of postpartum mood.

“Subjective perception of sleep shared a much stronger relationship with mood,” said lead author Bei Bei. “Women who are concerned about their sleep and/or mood should speak to health care professionals about cognitive-behavioral therapy.”

Bei said that pregnancy is a joyous and exciting time. But it also exposes women to many stressors, including disturbed sleep.

The authors reported that new moms often have a mild mood disturbance a few days after delivery. This is called the “baby blues.”

It tends to involve mood swings and tearfulness. Other symptoms such as irritability, anxiety and headaches may occur. Postpartum blues may last about a week.

Some moms may experience postpartum depression. This involves more severe mood changes that can impair daily functioning. The Office on Women’s Health reports that about 13 percent of pregnant women and new mothers have depression.

Last year a study found a hormonal link between restless legs syndrome and pregnancy.

Read more about sleep and pregnancy on SleepEducation.com. Get sleep tips for new parents from the AASM.

Sleep, Traumatic Injuries & Mental Health

A new study evaluated how sleep problems prior to a traumatic injury may affect mental health. The results were published in the Jan. 1 issue of the journal Sleep.

The study was performed in Australia. It involved 1,033 people who had a traumatic injury. They spent an average of 12.5 days in the hospital.

About 65 percent were hurt in a motor-vehicle accident. Fifteen percent were injured in a traumatic fall. Seven percent had an industrial accident. And six percent were victims of assault.

An initial assessment took place during their hospital admission. This included an evaluation of sleep disturbance in the two weeks prior to the injury. They were re-assessed three months later.

Results show that mental health problems were common at the three-month follow-up. Thirty percent of people who had no prior disorder developed a new psychiatric disorder after the injury.

The most common disorders were major depression and agoraphobia. Other common disorders were PTSD and generalized anxiety disorder.

Data analysis found that sleep impairment prior to the injury was a risk factor for the development of a mental health disorder. People with disturbed sleep prior to trauma were two times more likely to develop a psychiatric disorder.

The risk was even greater for people with no history of mental health problems. They were three times more likely to develop a psychiatric disorder if they had sleep problems prior to the trauma.

The authors suggested that sleep problems may limit your ability to manage stress after a traumatic event. Poor sleep may reduce your emotional, mental and physical resources. This may hinder your recovery.

They also noted that sleep problems may have contributed directly to the traumatic injuries. Disturbed sleep can result in fatigue, poor concentration and slow reaction times.

In November the Sleep Education Blog reported that the higher rate of insomnia in women may be linked to mental health problems such as depression. Read more about sleep and depression.

Get help for a sleep problem at an AASM-accredited sleep center near you.

Image by Joe

Teen Depression & Suicide: Sleep, Early Bedtimes Protect Adolescents

A new study shows that teens who go to bed early and get enough sleep may be less likely to suffer from depression and have suicidal thoughts. The results were published in the Jan. 1 issue of the journal Sleep.

The study involved 15,659 adolescents in grades seven to 12. Data were collected from the teens and their parents.

Teens who reported that they usually sleep for five hours or less per night were 71 percent more likely to suffer from depression. They also were 48 percent more likely to think about committing suicide than teens who reported getting eight hours of nightly sleep. Both depression and suicidal thoughts were less likely in teens who reported that they “usually get enough sleep.”

Teens were more likely to have problems if their parents set a weeknight bedtime of midnight or later. They were 24 percent more likely to suffer from depression than teens who had to go to bed at 10 p.m. or earlier. They also were 20 percent more likely to think about committing suicide.

Teens with a bedtime of 10 p.m. or earlier got the most sleep. They reported sleeping for an average of eight hours and 10 minutes per night. This was 40 minutes more than teens with a bedtime of midnight or later.

“Our results are consistent with the theory that inadequate sleep is a risk factor for depression,” lead author James E. Gangwisch, PhD, told the AASM. “Adequate quality sleep could therefore be a preventative measure against depression and a treatment for depression.”

Seven percent of participants had symptoms of depression. Thirteen percent reported that they seriously thought about committing suicide during the past 12 months.

The NIMH notes that girls are twice as likely as boys to have had a major depressive episode by age 15. But males are much more likely than females to commit suicide. In 2006 suicide was the third-leading cause of death for young people between 15 and 24 years old.

Parents reported setting a wide range of bedtimes. Fifty-four percent of parents reported that their teen had to go to bed by 10 p.m. or earlier on weeknights. Twenty-one percent reported setting a bedtime of 11 p.m. Twenty-five percent reported setting a bedtime of midnight or later.

And most teens complied with the bedtime that their parents set. Seventy percent of teens reported going to bed on time. Overall, teens reported going to bed only about five minutes later on average than their bedtime.

The AASM reports that most teens need a little more than nine hours of sleep each night to feel alert and well rested during the day. But a shift in the timing of their body clock causes teens to feel sleepy later at night. This explains why it can be hard for them to fall asleep before 10 p.m.

In August the Sleep Education Blog reported that a teen’s sleep pattern may be a marker of his or her risk for developing depression. Parents can get tips for teen bed times on SleepEducation.com.

Bipolar Disorder in Children May Be Linked to a Circadian Clock Gene

A new study found that the circadian clock gene RORB may be involved in bipolar disorder in children.

The study analyzed the genetic make-up of 305 children with bipolar disorder. They were compared with 140 controls.

Results show a positive association between bipolar disorder and four variants of the RORB gene. The authors suggest that this gene may be an important target in the search for the molecular basis of bipolar disorder.

The study also notes that bipolar disorder often involves a decreased need for sleep. This symptom helps discriminate children with bipolar disorder from those with ADHD.

The NIMH reports that bipolar disorder is a brain disorder. It is also known as manic-depressive illness.

It causes unusual shifts in mood, energy, activity levels and the ability to carry out daily tasks. These symptoms tend to be severe.

Bipolar disorder often develops in a person's late teens or early adult years. But some people have their first symptoms during childhood.

The disorder tends to run in families. Children are four to six times more likely to develop bipolar disorder if a parent or sibling has the illness.

Currently there is no cure for bipolar disorder. But ongoing treatment can help control the mood swings and other symptoms.

In 2008 FRONTLINE reported that bipolar disorder was long believed to exist only in adults. But in the mid-1990s it began to be diagnosed at much higher rates in children. Now one million children in the U.S. have been diagnosed with bipolar disorder.

Earlier this year the Sleep Education Blog reported that sleep problems in children may predict the future onset of depression. Learn more about sleep and children.

Image by Art & Line

Insomnia & Depression in Women

A new study examined why insomnia is more common in women than men.

The study analyzed data from the National Health and Nutrition Examination Survey. The survey is unique in that it combines interviews and physical exams.

The sample involved 5,469 young adults; their age ranged from 20 years to 39 years.

Results show that 16.7 percent of women reported insomnia symptoms; 9.2 percent of men had an insomnia complaint.

Why are women more likely than men to have insomnia? The study suggests that mental health is a key factor.

The gender difference in the odds of insomnia was no longer significant after adjusting for history of mental health conditions. The authors concluded that the higher rate of insomnia in women may be linked to mental health problems such as depression.

The NIMH reports that depression is also more common among women than men. This may be explained in part by hormonal factors that are unique to women.

The AASM reports that insomnia is seen in up to 85 percent of people with a major depressive episode. Frequent awakenings during the night are typical; waking up early in the morning and being unable to go back to sleep also is common.

Often the insomnia complaint is among the earliest symptoms to appear in a person with a mental health disorder. People often attribute their mental symptoms to poor sleep.

Read more about sleep and depression. Learn more about insomnia due to mental disorder on SleepEducation.com.

Teen Depression: Sleep Cycle is a Risk Marker

A recent study shows that a teen’s sleep pattern may be a marker of his or her risk for developing depression.

The study involved 48 teens who were “at risk” for depression; they had a high risk because of a parental history of depression. The at-risk teens were compared with 48 other teens in a control group; these teens had no personal or family history of a mental health problem.

The research team monitored the sleep cycles of the teens for three days. They also used lab tests to measure levels of the hormone cortisol; increased cortisol levels are related to depression in adults. The teens were monitored for up to five years.

Results show that the at-risk teens took less time to enter the stage of rapid eye movement sleep – or REM sleep. They also had more REM sleep and elevated cortisol levels. These teens were more likely to develop depression by the end of the five-year study period.

Previous studies had shown that depressed adults enter REM sleep earlier in the sleep cycle; but it was unclear if this pattern also occurred in teens.

“This study is an initial step in determining baseline measures that differentiate healthy adolescents from those who are likely to develop depression,” lead author Dr. Uma Rao said in a UT Southwestern Medical Center statement.

Rao cautioned that REM sleep and cortisol levels are not diagnostic tools; but they are “vulnerability markers” for depression.

“If we can identify factors such as sleep and cortisol and their role, we could start the prevention process,” she said.

The NIMH reports that depression often occurs along with another disorder in teens; examples include anxiety, eating disorders and substance abuse. By age 15, girls are twice as likely as boys to have had a major depressive episode.

Earlier this year the Sleep Education Blog reported that sleep problems in children may predict the future onset of depression. A study showed that sleep problems at age 8 predict depression at age 10; but depression at age 8 did not predict sleep problems at age 10. The study found a strong genetic link for the presence of sleep problems.

Obstructive Sleep Apnea & Depression

A new study examined the rate of obstructive sleep apnea in people with major depressive disorder and insomnia.

The study involved 51 people with both depression and insomnia; they were evaluated by an overnight sleep study.

Results show a high rate of OSA in people with depression and insomnia; 39 percent of the people had an apnea-hypopnea index (AHI) of 15 or more breathing pauses per hour of sleep. An AHI of 15 to 30 is considered “moderate” sleep apnea.

Men were more likely than women to have OSA. People with sleep apnea also were older and had a higher body mass index (BMI).

Previous studies also have linked sleep apnea to depression.

A 2008 study in the Journal of Clinical Sleep Medicine involved 1,106 adults with sleep apnea. About 19 percent of the men and 37 percent of the women had depression.

A 2006 study involved 788 men and 620 women. Results show that people with mild sleep apnea were two times more likely to have depression than people without OSA. The risk of depression was even higher in people with moderate or severe sleep apnea.

The good news is that treating sleep apnea can reduce the symptoms of depression.

A 2007 study in the Journal of Clinical Sleep Medicine examined the effects of CPAP therapy on depression. The AASM recommends CPAP as the treatment of choice for people with sleep apnea.

The study involved 50 adults with severe sleep apnea. Four to six weeks of CPAP therapy lowered depression symptoms in 94 percent of the group.

This improvement was long lasting; after one year of CPAP therapy, 88 percent of the group still had lower symptoms of depression.

Get help for sleep apnea at an AASM-accredited sleep center near you. Learn more about the link between sleep apnea and depression on SleepEducation.com.

Risk of Depression in “Evening Types” and “Morning Types”

A new study examines how chronotype may be related to depression. Is the risk of depression greater in “evening types” (“night owls”) or “morning types” (“morning larks”)?

The study involved 200 healthy adults between the ages of 18 and 99 years. Results show that people who are “evening types” have a higher risk of severe depressive symptoms.

MSNBC reports that evening types went to bed around midnight; morning types went to bed around 11 p.m. and woke up about 40 minutes earlier. Total sleep time was about the same for the two groups.

The study was unable to show if sleep schedule causes depression. But it suggests that going to bed and waking up a little earlier could improve your mood.

Yet making a change may not be easy; your DNA has a strong influence on when you prefer to sleep.

Learn more about evening and morning chronotypes.

Do the Babies of Depressed Moms Have More Sleep Disturbances?

A small study in the journal Sleep examined the sleep of babies born to mothers who struggle with depression.

Results show that these babies are more likely to have disturbed sleep at 2 weeks of age. These sleep problems remain present at the age of 6 months.

The study involved 18 healthy, full-term babies. Seven “low-risk” infants were born to women with no history of depression. Eleven “high-risk” babies were born to women diagnosed with depression or with high levels of depression symptoms.

Babies born to depressed moms took an hour longer to fall asleep at night. They also had shorter periods of sleep. Their average total sleep time during a 24-hour period was similar to the “low-risk” babies. But their nightly sleep was 97 minutes shorter; during the daytime they had more sleep episodes of a shorter average duration.

Are these sleep problems directly linked to the mother’s depression? Is it the mother’s hormone levels that affect the infant’s sleep? This is still unclear, study author Roseanne Armitage, PhD, told the AASM.

“Whether it is maternal hormones that ‘cause’ the sleep problems in infants is not yet known,” she said. “It could be genetic, hormonal, or both.”

But Armitage thinks that it is possible to improve the sleep of babies born to depressed moms. A behavioral or environmental intervention may be helpful.

Learn more about how to help your infant sleep better on SleepEducation.com.

Sleep Problems & Depression in Children

Sleep problems and depression often are linked together. But which one comes first? Do sleep problems cause depression? Or is it the other way around?

The relationship is a complex one. But a new study in the journal Sleep shows that sleep problems in children may predict the future onset of depression.

The study involved 300 pairs of twins. They were evaluated for sleep problems and depression at 8 years of age and again when they were 10.

Results show that sleep problems at age 8 predict depression at age 10; but depression at age 8 did not predict sleep problems at age 10. There was a strong genetic link for the presence of sleep problems.

Parents completed a short version of the Children’s Sleep Habits Questionnaire. It helps identify eight common sleep problems in children:

• Bedtime resistance
• Sleep-onset delay
• Sleep duration
• Sleep anxiety
• Night waking
• Parasomnias
• Sleep-disordered breathing
• Daytime sleepiness

The AASM recommends that school-age children get about 10 to 11 hours of sleep each night. Getting help for sleep problems early on may prevent other problems from developing.

Contact an AASM-accredited sleep center if your child has an ongoing sleep problem. Learn more about sleep and children here.

More Young Adults Using Sleeping Pills

The New York Times reports that the use of sleeping pills by young adults has risen dramatically. The biggest increase from 1998 to 2006 came among adults between the ages of 18 and 24.

The report is based on an analysis by Thomson Reuters. It examined drug claims by adults under the age of 45. Overall sleeping pill use was highest among adults between the ages of 35 and 44.

The most popular sleeping pills were Ambien CR and Lunesta. The drugs were prescribed for an average of 93 days.

AASM president Dr. Mary Susan Esther told the Times that chronic insomnia often is linked to other problems. These include depression and anxiety. In these cases a sleeping pill won’t address the related problem.

Insomnia also can be caused by disruptions to the sleeping environment. This is called environmental sleep disorder. Dr. Esther pointed out that a noisy dorm is a common sleep disrupter for college students.

The report did not examine the use of other treatments for insomnia. One of the most effective treatments is cognitive behavioral therapy. Following the tips of good sleep hygiene also helps some people with insomnia.

Like any other drug, sleeping pills may cause some side effects. These side effects can include sleepwalking, sleep eating and other complex sleep behaviors. Some people also may experience memory problems.

The AASM offers these Guidelines for Taking Sleep Medications. Contact your doctor or pharmacist if you have any other questions about taking sleeping pills.

Do the Winter Blues Make You SAD?

Only 74 more days until March 20. What some people like to call the "vernal equinox." You know, the first day of spring.

But who’s counting, right? Certainly not people in states like Arizona, Nevada or California. There the sun is always shining. Or so it seems.

For the rest of us, there is winter. For some of us, there is a very long winter. Dark. Gray. Dreary. Cold – miserably cold. And depressing.

This kind of winter depression is called seasonal affective disorder (SAD). It may surprise you that SAD has little to do with how cold it is. Instead it’s all about sunlight. Or the lack of it, to be exact.

Sunlight is an important visual cue for your body. It lets your brain know that it is "showtime." Time to be awake, alert and active. Your brain responds by adjusting your body temperature and certain hormone levels.

The long, dark days of winter deprive your body of this signal. As a result, you may feel sluggish, sleepy and depressed. Like other forms of depression, SAD is more common in women.

To combat SAD the best thing you can do is to "see the light." Let your eyes see as much sunlight as possible. Sit by a window during the day. Go outside for a walk on your lunch break.

You can supplement this natural light with bright light therapy. In the morning you sit near a small "light box" at home for a specific length of time. This exposes your eyes to intense but safe amounts of bright light.

A study in 2007 also found that cognitive behavioral therapy can be an effective treatment for SAD. It can be used alone or together with light therapy. Some medications also may help treat SAD.

As with any other medical problem, you should discuss SAD with your doctor. He or she can develop a treatment plan for you.

What are you doing to cope with SAD this winter?