Seasonal Affective Disorder (SAD)
Seasonal affective disorder (SAD), also called winter depression, winter blues, summer depression, and seasonal depression, is a mood disorder subset in which people who have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year, most commonly in the winter.
Seasonal affective disorder (SAD) is a form of depression that the NHS estimates to affect approximately one in 15 people in the UK between September and April.
It can be particularly severe during December, January and February. For some people, SAD is so disabling that they cannot function in winter without continuous treatment. Others may experience a milder version called sub-syndromal SAD or 'winter blues'.
It occurs throughout the northern and southern hemispheres but is extremely rare in people living within 30 degrees of the Equator, where daylight hours are long, constant and extremely bright.
What are the symptoms of SAD?
SAD may begin at any age, but it most commonly starts between 18 and 30. Symptoms generally appear between September and November and continue until March or April, when there may be a sudden burst of energy and activity accompanying the longer, brighter spring and summer days. A diagnosis is usually made after you've experienced two or more consecutive winters of symptoms.
Common symptoms include:
• sleep problems - usually oversleeping and difficulty staying awake but in some cases disturbed sleep and early morning waking
• lethargy - lacking in energy and unable to carry out normal routine due to fatigue. Heaviness in the arms and legs
• overeating - craving for carbohydrates and sweet foods, which usually leads to weight gain
• depression - feeling sad, low and weepy, a failure, sometimes hopeless and despairing
• apathy - loss of motivation and ability to concentrate
• social problems - irritability and withdrawal from social situations, not wanting to see friends
• anxiety - feeling tense and unable to cope with stress
• loss of interest in normally pleasurable activities
• loss of libido - decreased interest in sex and physical contact
• weakened immune system - vulnerability to catching winter colds and flu
• mood changes - for some people bursts of over-activity and cheerfulness (known as hypo-mania) in spring and autumn.
What causes SAD?
The exact cause of SAD isn't fully understood, but it's often linked to reduced exposure to sunlight during the shorter autumn and winter days.
The main theory is that a lack of sunlight might stop a part of the brain called the hypothalamus working properly, which may affect the:
• production of melatonin – melatonin is a hormone that makes you feel sleepy; in people with SAD, the body may produce it in higher than normal levels
• production of serotonin – serotonin is a hormone that affects your mood, appetite and sleep; a lack of sunlight may lead to lower serotonin levels, which is linked to feelings of depression
• body's internal clock (circadian rhythm) –your body uses sunlight to time various important functions, such as when you wake up, so lower light levels during the winter may disrupt your body clock and lead to symptoms of SAD
It's also possible that some people are more vulnerable to SAD as a result of their genes, as some cases appear to run in families.
Seasonal affective disorder is diagnosed more often in women than in men. And SAD occurs more frequently in younger adults than in older adults.
Factors that may increase your risk of seasonal affective disorder include:
• Family history. People with SAD may be more likely to have blood relatives with SAD or another form of depression.
• Having major depression or bipolar disorder. Symptoms of depression may worsen seasonally if you have one of these conditions.
• Living far from the equator. SAD appears to be more common among people who live far north or south of the equator. This may be due to decreased sunlight during the winter and longer days during the summer months.
Take signs and symptoms of seasonal affective disorder seriously. As with other types of depression, SAD can get worse and lead to problems if it's not treated. These can include:
• Social withdrawal
• School or work problems
• Substance abuse
• Other mental health disorders such as anxiety or eating disorders
• Suicidal thoughts or behavior
Treatment can help prevent complications, especially if SAD is diagnosed and treated before symptoms get bad.
Seasonal affective disorder seems to develop from inadequate exposure to bright light during the winter months. Studies show that bright light changes the chemicals in the brain. Exactly how this occurs and the details of its effects are being studied. Factors like high levels of melatonin and low levels of serotonin in the brain, as well as low levels of vitamin D levels in the blood are found to be associated with a higher occurrence of seasonal affective disorder and some other depressive conditions.
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