Seasonal affective disorder (SAD) is now more commonly known as seasonal major depressive disorder. This is a type of depression that affects people living in countries farther from the equator. It is most common during the winter months and tends to disappear in the spring.
Other names for seasonal major depressive disorder include SAD, winter depression, and seasonal depression.
According to the American Psychiatric Association (APA), this condition affects about 5% of people in the United States.
Symptoms can last about 40% per year.
In this article, we’ll look at how the condition develops, who may be at risk, and what treatment options are available.
What is SAD?
People with SAD or seasonal major depressive disorder experience depressive symptoms with increasing frequency as the days get shorter. These symptoms gradually improve in early spring when the amount of sunlight increases.
The APA suggests this can occur when reduced exposure to sunlight causes a chemical imbalance in the brain. However, more research is needed to confirm the cause.
Seasonal changes in sunlight affect circadian rhythms that regulate our sense of timing. Some people see this as their “internal biological clock,” and disrupting the circadian rhythm can significantly impair mood.
According to Harvard Medical School, women experience SAD more often than men. SAD also develops more often in younger people than older people.
It is also more common in people living further north of the equator, as winter shortens the daylight hours even more in these areas.
Less commonly, some people experience SAD during the summer months.
SAD symptoms are similar to those of depression. The main difference is that symptoms develop as winter approaches and decrease in spring.
For most people, symptoms come and go at the same time each year.
As autumn approaches and daylight decreases, symptoms are usually mild. The severity, characteristics, and patterns of SAD can vary greatly from person to person.
Signs and symptoms of SAD typically include:
- anxious feelings that don’t match their cause or trigger
- feelings of guilt and worthlessness
- stress and irritability
- difficulty making decisions
- reduced concentration
- constant bad mood
- decreased libido
- restless activities such as walking
- crying, often without an obvious trigger
- feeling tired even after a good night’s sleep
- sleep too long
- increased appetite
- social isolation and decreased interest in activities that were once enjoyable
- difficulty concentrating
- overeating and possible weight gain
- suicidal thoughts
In people who experience SAD as a result of seasonal psychosocial stressors, a doctor may not be able to diagnose the condition. For example, seasonal workers may be unemployed during the winter months and may show some symptoms of depression as a result.
Some people experience these symptoms in the summer rather than in the winter, and the symptoms go away in the winter. However, SAD is most common during the winter months.
Certain factors can influence your risk of developing SAD. We’ll discuss this in more detail below:
Women are more likely than men to have SAD, but this may be associated with a higher prevalence of general depression in women.
According to a 2015 review in the journal Depression Research and Treatment, SAD diagnoses are four times more common in women than in men.
The National Institute of Mental Health (NIMH) suggests that living further from the equator may increase your risk of developing SAD.
People living in areas where the days in winter are much shorter are more susceptible.
Having close family members with a history of other types of depression may increase the likelihood of developing SAD.
Personal history of depression
People with a history of depression or bipolar disorder, or those currently suffering from any of these conditions, are more likely to develop SAD.
However, a doctor will only diagnose SAD if symptoms of depression become more frequent during a particular season each year.
Experts are still not sure about the exact causes of SAD. However, studies have pointed to the following factors:
Decreased production of serotonin in winter
Serotonin is a neurotransmitter that plays a key role in regulating mood. It binds to a specific protein to circulate in the body.
This protein is usually reduced during the winter months to protect a person from seasonal environmental stress.
However, a 2016 long-term study in the journal Brain found that people with SAD did not experience a decrease in serotonin transporter levels during the winter months. The risk is particularly high in people prone to mood disorders.
impaired melatonin levels
Melatonin is a hormone that affects sleep and mood.
The NIMH claims that reducing exposure to sunlight during the short winter days upsets the body’s balance of melatonin.
Decreased Vitamin D Production
A 2018 rat study published in the journal Genes & Nutrition found links between vitamin D and serotonin, which may explain the onset of depression in some people.
The body produces vitamin D after exposure to sunlight. Less sunlight during the winter months may explain the depressive symptom cycle of SAD.
The doctor may ask the following questions to determine if you have SAD:
- How long do a person’s symptoms last?
- How serious are the symptoms?
- How do they affect daily activities?
- Are there any changes in your sleeping or eating habits?
- Can a person identify changes in thinking and behavior during different seasons?
- Can they provide information about any relevant family history, such as a loved one with depression, bipolar disorder, or other mood disorders?
Because there are several types of depression, it may take some time for a doctor to accurately diagnose SAD. There are no medical or laboratory tests to diagnose this condition. However, your doctor may order certain diagnostic tests, including blood tests, to rule out other diseases or underlying conditions.
The APA, Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) does not classify SAD as a separate disorder. Instead, SAD is the “course token”.
A healthcare provider will only diagnose SAD if the person has symptoms of major depressive disorder that develop and resolve at a certain time each year.
According to the APA, a person can relieve SAD symptoms by increasing their exposure to sunlight. For example, long walks with a little more sunlight can help.
Treatment for SAD usually includes medication, therapy, and light box therapy.
Lifestyle adjustments can also help reduce the effects of SAD.
Although SAD seems to result from changes in brain chemistry, therapy that focuses on mood and behavior can also help. The APA suggests that this type of therapy may have a longer-lasting effect than using medication or using a light box to manage mood.
Cognitive Behavioral Therapy (CBT) can help people more effectively monitor and control their response to certain situations and conditions. If a person can perceive events, their behavior will also change over time.
This can help reduce the severity of SAD’s symptoms during the season when the effects are at their maximum.
A cognitive behavioral therapy course usually includes a personalized program of mental and breathing exercises to help the person identify and alleviate negative emotions.
People can attend group or joint CBT sessions. These sessions provide support and advice to those living with people with SAD.
Bright light therapy
If a person’s symptoms are severe enough to interfere with daily life, a doctor may recommend bright light therapy.
Also known as phototherapy, this intervention can help restore a person’s circadian rhythms.
In bright light therapy, a person sits in front of a special light box for a set amount of time each day between early fall and spring. UV lamps, full spectrum lamps, and tanning lamps will not have the same effect on people with SAD.
NIMH recommends using the light box as soon as possible after waking up.
Generally, people should receive light therapy for 20-60 minutes a day, depending on the intensity of the light.
Some people with SAD find that increased exposure to natural sunlight can help relieve symptoms. Examples include opening blinds and curtains, pruning trees around the house, and sitting close to a window during the day.
Going outside every day and being outside for extended periods of time, socializing and being active can help. The seasonal nature of SAD means that planning ahead for the season can help reduce its impact on daily life.
Likewise, regular exercise and eating a balanced, nutritious diet are also great for overall health. They can also help a person relieve anxiety symptoms and maintain a more regular sleep cycle.