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Seasonal depression symptoms causes and treatment

The seasonal depression or seasonal affective disorder (TAF) is a depression linked to lack of natural light. In order to be medically referred to as seasonal depression, depression must occur at the same time each year, in the fall or winter, for at least two consecutive years, and last until the following spring.

During the winter period, the days are short and the brightness less intense. It would go from 100,000  lux (a unit of measure of brightness) on sunny summer days to sometimes just 2,000 lux on winter days.

Who is affected?

In Canada, about 18% of people experience a “winter blues” characterized by a lack of energy and a more fragile morale . Some people live this phenomenon more intensely. With a real seasonal depression , they may have difficulty doing their usual activities. This is the case of 0.7 to 9.7% (36) of the adult population in North America.

In Europe, studies of seasonal depression would concern 1.3 to 4.6% of the population. But the method of calculation depends on the objective criteria.

The majority, between 70 and 80% of those affected are women . Children and adolescents are more rarely affected.

The further away from the equator, the greater the number of people affected, because the number of hours of sunshine fluctuates more during the year. For example, in Alaska, where the sun does not rise at all for more than 1 month during the winter, 9% of the population suffers from SAD.

In people with classic depression or bipolar illness (with depressive episodes), depression has a seasonal exacerbation in 10 to 15% of people with the disease.

As with classic depression , the symptoms of seasonal depression can worsen to the point of suicidal ideation .

Seasonal depression in the summer?

Some people have seasonal depression in the middle of the summer. This can be due to the heat,sometimes  difficult to support or the  high brightness . No specific treatment has been designed for people who suffer from seasonal summer depression. Doctors offer standard treatment for depression ( psychotherapy , antidepressant drugs). Some people manage to relieve their symptoms with an air conditioning system and reducing the ambient light in their home, or traveling in temperate regions .

Causes of Seasonal depression

The relationship between light and depression. He defined seasonal depression . In fact, the “discovery” of this type of depression is inseparable from the invention of light therapy . By noting that exposure to broad – spectrum artificial light could benefit people with depressive symptoms during the winter season, Dr. Rosenthal was able to demonstrate the role of lightness on the internal biological clock and the mood.

Indeed, light plays an important role in the regulation of the internal biological clock. It controls several body functions according to specific rhythms, such as waking and sleeping cycles and the secretion of various hormones according to the time of day.

After entering the eye, the light rays turn into electrical signals that, once sent to the brain, act on the neurotransmitters . One of these, serotonin , sometimes called the “happiness hormone,” regulates mood and governs the production of melatonin , another hormone responsible for wake-sleep cycles. The secretion of melatonin is inhibited during the day and stimulated during the night. The hormonal imbalances caused by a lack of light can be significant enough to cause symptoms related to  depression .

Degree of brightness: some benchmarks

Sunny summer day: from 50,000 to 130,000 lux

Sunny winter day: from 2,000 to 20,000 lux

Inside a house: from 100 to 500 lux

In a well-lit office: from 400 to 1,000 lux

Symptoms of Seasonal depression

The following symptoms always occur at the same time of year, from October to March, but especially in November , December and January . They disappear gradually in spring or spontaneously during a trip under the sun.

  • A sad mood presents every day all day, irritability.
  • A decrease in the pleasure experienced during activities or situations that usually lead to pleasure.
  • A state of chronic fatigue and drowsiness during the day, difficulty getting up in the morning.
  • A loss of interest and a lack of initiative.
  • A lack of concentration, a difficulty in making decisions.
  • A higher degree of stress: this condition can lead to compensatory behaviors such as increased alcohol consumption or uncontrollable cravings for sugary foods that can lead to weight gain.
  • An impression of being slowed down or, on the contrary, agitated.
  • An increased need for sleep.
  • A drop in productivity at school or at work.
  • A drop in libido.
  • A tendency to isolate oneself.
  • A feeling of worthlessness, guilt.
  • Black thoughts, thoughts of death or even suicidal thoughts.

People at risk

  • Those of whom a close family member (father, mother, brother, sister) has suffered from seasonal depression.
  • Women at higher risk than men.
  • People living in countries where sunshine is low in winter.
  • People with an indoor craft preventing them from seeing the light of day in winter.

Risk factors for Seasonal depression

  • Live in a country that is far from the equator.

Prevention of seasonal depression

Why prevent?
  • To reduce the symptoms of seasonal depression
  • To have more energy and a better mood during the months when the hours of sunshine are at their lowest.
Basic preventive measures
Bath of natural light

  • Take the air at least 1 hour a day and a little longer the gray days, even during the winter. Indoor lighting is very different from the light spectrum of the sun and does not have the same effect as the outside light.
  • Allow maximum sunlight to penetrate inside your home. Walls of pale colors certainly increase the brightness of a room. You can also place some mirrors in strategic places.

Physical exercise

If exercised outdoors, in the light of day, physical exercise helps prevent seasonal depression. The practice of winter sports also adds a note of pleasure.

Light Therapy

See the Therapies section.

Other preventive measures
Fish consumption

Among Icelanders, there is little seasonal depression  compared to other northern peoples. Some researchers attribute this to their high consumption of fish and seafood sea. These are rich in omega-3 fatty acids, nutrients that seem to counteract depression. Some factors related to genes also help to keep the farthest Icelanders this form of depression. These are still hypotheses. At present, it is unclear what effect can have omega-3 consumption on symptoms of SAD.

Medical treatments for seasonal depression

If you think you are suffering from seasonal depression , it is best to consult a doctor to make a clear diagnosis.

Since seasonal depression is a result of a lack of light , it is usually enough to fill this gap to regain its energy.

Light Therapy

Spending time outdoors is usually insufficient to treat seasonal depression, given the lower intensity of sunlight during the fall and winter. However, people whose symptoms are mild may feel the benefits .

Light therapy is a form of phototherapy (a therapy that uses light) that simply exposes people to a high-intensity white light at a fixed time every day.

It is recommended to expose 30 to 45 minutes per day to a lamp with a luminous intensity of 10,000  lux . It is suggested to start gradually with sessions of 10 to 15 minutes per day. In addition, it is recommended to do the treatment in the morning rather than in the evening 4 .

Attention, this type of lamp has nothing to do with lamps producing UV.

For the treatment of children and adolescents , the duration should be less, that is to say about 15 to 20 minutes per session.

Several studies confirm the efficacy of light therapy. It seems to be effective for the majority of people who try it. Some sources report that up to 85% of people diagnosed benefit . The response rate, however, varies from one study to another. In people who respond to treatment, the symptoms would be reduced by about half. This rate is comparable to that of antidepressant drugs , but light therapy produces far fewer side effects and is less expensive.

In general, symptomatic relief is felt after 2 to 4 days of light therapy , but 4 weeks of use are usually required before a clear improvement and measurable biological changes can be seen.

Ideally, the treatment starts in September or October and continues until spring. Some people may also feel the need in the summer if Gray made several days in a row. The most affected individuals may experience a return of symptoms only after 2 or 3 days of stopping treatment. Thus, it is better to decrease its exposure gradually.

The white light has beneficial effects on the symptoms of SAD. By entering the eye, it sends chemical messages to the region of the brain that regulates the biological rhythms and the production of various hormones.

Practical advice

  • To be effective, light therapy must be performed with a lamp specifically designed for this purpose. When buying, make sure that it is a 10,000 lux lamp (a 2,000 lux lamp, for example, although less expensive, requires an exposure time 5 times longer to obtain the same effect, so about 2 hours 30 minutes daily). Also, it must be ensured that the lamp emits a complete light spectrum , and that it does not expose to ultraviolet rays.
  • The light source should be placed at eye level, at a distance of 40 cm to 60 cm.
  • It is not recommended to look at the lamp directly.
  • Some personal or group insurance programs reimburse all or part of the cost of the light therapy lamp (which ranges from $ 200 to $ 500 or $ 100 to $ 200), at the doctor’s prescription.


  • Possible side effects . Light therapy can cause headaches, sedation or agitation. These effects are usually not very pronounced and disappear over time. Just reduce the exposure time slightly if necessary.
  • Possible contraindications . Light therapy can cause eye pain or other eye problems. Glaucoma users, those taking lithium, and the elderly should consult their ophthalmologist or doctor before beginning light therapy.
Blue light lamps: effective?

There are commercially available portable lamps called “new generation”. They emit only a blue light . According to their manufacturer, they would have the advantage of offering a treatment of shorter duration than white light therapy at 10 000 lux (15 to 20 minutes per day rather than 30 minutes). In addition, it boasts their ease of use, because these lamps are compact and lightweight.

Manufacturers attest that it is not necessary to expose oneself to the full spectrum of white light to act on the circadian cycle hormones. The blue light would be the one that would exert the most important effect. According to the manufacturers, the efficacy of light therapy would depend on the wavelength emitted rather than the luminous intensity (in lux ). Thus, these lamps emit mainly rays whose wavelength is between 446 nm and 520 nm, that of the blue color. Their luminous intensity is 2,500 lux or less.

The effectiveness of blue light in treating seasonal depression has not yet been proven. “The body of research indicates that the best therapeutic effect is achieved with the complete light spectrum of 10,000 lux white light. “We need more studies to evaluate the effectiveness of blue light,” he adds.

Only a few clinical trials have tested the efficacy of the blue light lamp. The results indicate a therapeutic effect superior to placebo. In his eyes, the effectiveness of exposure to blue light is less than that of conventional light therapy. That said, no study has yet compared the effectiveness of these two types of lamps.


Artificial simulation of dawn

Artificial simulation of dawn is another form of phototherapy that reproduces the natural conditions of awakening by simulating the brightness of a sunrise. In practice, simply swap its alarm clock for a “dawn lamp” programmed to illuminate the room gradually, at the desired time.

A meta-analysis published in 2005 concluded that the effectiveness of the artificial dawn simulation to decrease the intensity of the symptoms of SAD . This meta-analysis is based on 5 clinical trials. That said, the efficacy of the artificial simulation of dawn has been tested through a smaller number of studies than conventional light therapy.

The mechanisms of action of the dawn simulator are not yet well understood. Certainly, they do not rely on the intensity of the brightness, since it is relatively low (the device works with a bulb of 60 watts).

On the market, there are different models of “dawn simulators” which can be set for the start time of the dawn and its duration. For example, for a sunrise at 7am, the light can be programmed to light up slowly from 6am or 6:30 am, and be at its maximum intensity at 7am. The majority of models also include a ringtone.

For more information, consult the Luminothérapie file.


The use of antidepressants (fluoxetine or Prozac, sertraline or Zoloft, venlafaxine or Effexor, paroxetine or Paxil, or bupropion or Wellbutrin) has been shown to be effective, especially if symptoms are pronounced. They can be used alone or with light therapy.

Some people prefer drugs to light therapy, for practical reasons. Medications are also a solution for people who do not have light therapy to relieve symptoms, or are downright inefficient.


Psychotherapy follow-up can help overcome seasonal depression by working on negative attitudes and behaviors.

Physical exercise 
Physical exercise works against all types of depression and has an effectiveness that can be comparable to that of antidepressants. In seasonal depression, the ideal is to start an outdoor exercise in order to benefit from both the “physical exercise” effect and the “daylight” effect.

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