Seasonal affective disorder, also known as SAD, is a type of depression that occurs in countries that are far away from the equator during the winter months.
SAD is sometimes called winter depression. As the mornings start later and evenings begin earlier when winter approaches, there is less total sunlight each day.
Experts say SAD is most likely caused only by lack of sunlight and not cold temperatures. Depressive symptoms usually build up slowly as days start getting shorter, and gradually subside in early spring, as the amount of environmental sunlight each day rises.
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You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on seasonal affective disorder
Here are some key points about SAD. More detail and supporting information are in the main article.
- SAD did not receive a clinical name until the early 1980s.
- The symptoms of SAD are similar to those of depression.
- Common symptoms include low mood, lethargy and social withdrawal.
- Females are more likely to experience SAD than males.
- People with close relatives who have had SAD are also more likely to develop the condition.
- SAD is diagnosed through consultation with a doctor.
- Raising exposure to sunlight may alleviate the symptoms of SAD.
- Antidepressant medication and psychotherapy can also help treat the condition.
What is SAD?
SAD was first mentioned, in any literature we have access to today, in 1845. However, the condition did not have a clinical name until the early 1980s.
We know that seasonal variations in sunlight intensity can have an impact on what animals do, from hibernating, reproducing and seeking out a mate. These seasonal changes in sunlight affect our circadian rhythms (biological internal clocks).
SAD is thought to affect about 7% of people in the UK, and is more common among young adults. It is more common in females than males. Approximately 8.9% of people in Alaska are believed to be affected by SAD, and 24.9% with subsyndromal SAD.
According to the British National Health Service (NHS), some people may have SAD during the summer, but this is very rare.
Symptoms of SAD
The symptoms of SAD are similar to those of depression and typically recur at the same time each year.
The signs and symptoms of SAD are similar to those of depression, but they typically come on as winter approaches, and gradually go away during springtime.
In the majority of cases, symptoms come back each year, at around the same time. Symptoms are usually mild as autumn advances, and gradually worsen as the amount of daylight goes down. SAD severity, characteristics and patterns can vary considerably from person-to-person.
About four-fifths of SAD patients develop unipolar depression, while the rest have bipolar. Unipolar means there are persistent depressive symptoms, while bipolar involves swinging from high (manic) to very low (depressive) periods.
The signs and symptoms related to SAD include:
- Feeling guilty and worthless
- Feeling stressed
- Low moods and despair
- Reduced libido
- Lethargy and fatigue
- Increased appetite
- Social withdrawal
- Difficulty concentrating
- Weight gain.
The signs and symptoms of Seasonal Affective Disorder are covered in our article, Seasonal affective disorder: could you spot the signs?
Who has a higher risk of developing SAD?
Sex: females are more likely to suffer from SAD than males. However, males tend to have more severe symptoms
Geography: the further you live from the equator, the higher are your chances of developing SAD. Put simply, those who live in places where days are considerably shorter in winter have a higher risk of developing SAD
Genetics: if you have a close relative who has or had SAD, your risk of having it yourself is greater
Having, or having had depression: patients with a history of depression or bipolar depression are more likely to suffer from SAD, that those with no such history.
Causes of SAD
Experts are still not sure what the exact causes of SAD are. However, studies have pointed to the following:
- Circadian rhythm - our body clock. Each of us has an internal body clock which tells us when to be awake and asleep. Less sunlight in the winter is thought to disrupt our circadian rhythm, which most likely results in depressive symptoms
- Melatonin levels - melatonin is a hormone which influences our sleep patterns and mood. Experts believe that reduced exposure to sunlight (shorter days) disrupts our melatonin balance. SAD patients produce higher amounts of serotonin during the winter months
- The hypothalamus - it is believed that sunlight stimulates the hypothalamus, a part of the brain that controls sleep, mood and appetite - three things that have an impact on our moods. Apart from disrupting melatonin levels, lack of sunlight may also affect the production of serotonin, a neurotransmitter (brain chemical) that affects mood. People with SAD during the winter months are said to have lower serotonin levels.
Recent developments on seasonal affective disorder (SAD) causes from MNT news
Researchers have hypothesized that reduced exposure to light can cause imbalances of brain chemicals called neurotransmitters, which affect mood. A University of Copenhagen research team builds on this theory and claims they have confirmed the biochemical cause of SAD.
A new study led by researchers from the University of Georgia associates low vitamin D levels with greater risk of seasonal affective disorder. The research team publish their findings in the journal Medical Hypotheses.
Seasonal affective disorder is believed to be triggered by seasonal changes in daylight, with the condition most prevalent during winter months. But what makes certain people more susceptible to such changes? Researchers say they have uncovered a gene mutation that could be responsible.
On the next page, we look at the diagnosis of SAD and the available treatment options for the condition.