Seasonal Affective Disorder

Seasonal affective disorder (SAD) is a type of depression that comes and goes with changing seasons. The overwhelmingly most common form begins in the fall and continues throughout the winter with symptoms resolving in the spring. SAD is likely related to the diminishment of daylight in the winter as well as chemical imbalances in the brain. Treatment can bring relief and may include light therapy, behavioral therapies, and the use of antidepressant medications.

What Is Seasonal Affective Disorder?

Seasonal affective disorder, or SAD, is a mood disorder and a type of seasonal depression that occurs most often in the winter months. There are rarer cases in which it is triggered by the summer months. Someone who has SAD will experience the onset of depression at about the same time each year. It typically resolves as the seasons change again. SAD symptoms are very similar to those of major depression, and according to the Diagnostic and Statistical Manual of Mental Disorders it is classified as a type of depression.

SAD is more than just feeling a little bit down because it is winter or the weather isn’t very nice. It is a serious mental health issue that triggers real symptoms of depression. There may be actual biological causes of SAD, and treatments that include both standard depression treatment, like medication and therapy, and the use of light can be effective in providing relief.

Types of Seasonal Affective Disorder

The majority of people who struggle with SAD each year experience what is called fall and winter SAD. This is a type of depression that sets in during the fall or winter months. The symptoms begin to resolve on their own as spring begins. The low light, as well as the colder weather of fall and winter, may be to blame for this type of SAD.

A rarer type of seasonal affective disorder is known as spring and summer SAD, or summer depression. For people with this type the symptoms of depression begin in spring, continue through the summer and only resolve naturally in the fall. It is essentially the opposite of the more common type of SAD that is triggered by the onset of winter.

People who have been diagnosed with bipolar disorder, a mood disorder characterized by cycling periods of depression and mania, may experience seasonal shifts that can resemble SAD. This is not considered SAD, but it can be similar. For some people with bipolar, spring and summer can trigger more mania and less depression, while the opposite occurs in fall and winter.

Facts and Statistics

SAD is more severe and serious than the “winter blues.” It is a real mental health condition that causes significant depression and affects hundreds of thousands of people every year.

Symptoms and Diagnosis of Seasonal Affective Disorder

Seasonal affective disorder can be diagnosed much like major depression is. A physical exam and blood tests to rule out any illnesses or nutritional deficiencies may be done first, but then a psychological evaluation is done to determine if a mental illness diagnosis can be made. This should be done by a mental health professional.

The diagnostic criteria for seasonal affective disorder include the symptoms of major depression as well as other signs of seasonal depression:

  • Feeling depressed most days and for most of the day
  • No longer having interest in once-enjoyable activities
  • Low energy and fatigue
  • Difficulty sleeping or sleeping more than usual
  • Changes in appetite, which may lead to weight gain or weight loss
  • Difficulty concentrating, making decisions, or getting things done
  • Feelings of hopelessness, guilt, and worthlessness
  • Thoughts of suicide
  • Feeling sluggish or heaviness in the arms or legs
  • Feeling agitated or irritable
  • Avoiding social situations
  • Cravings for foods high in sugar or starch

Some of the SAD symptoms that are more common in the fall and winter type of the condition are oversleeping, craving sweet and starchy foods, weight gain, and fatigue. Spring and summer SAD tends to cause more insomnia, loss of appetite and weight loss, and anxiety, agitation or irritability.

Experiencing the occasional bad mood in the winter or feeling down sometimes because of the weather or the short days is normal. It does not necessarily indicate SAD. However, when these feelings persist and there are symptoms of depression that go beyond simply feeling down or blue, it may be time to be evaluated for a possible SAD diagnosis.

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Causes and Risk Factors

Like other mental illnesses and major depression, it is not possible to determine one single cause of seasonal affective disorder. However, this is a unique type of depression that is clearly related to the changing seasons, which gives experts clues as to what may trigger it in some people and not others. As with other types of depression, neurotransmitters, which are chemical messengers in the brain, are likely to play a role. Serotonin, for instance, which helps regulate mood, may drop in the winter as levels of sunlight decrease.

Another neurotransmitter, melatonin, may also be implicated in the onset of SAD. Production of melatonin is triggered by darkness and is what helps people sleep when it gets dark outside. Studies have found that people with SAD produce significantly more melatonin during the winter months, as compared to people who do not have SAD. Extra melatonin may cause someone to feel sleepier and more lethargic.

There is also evidence that vitamin D may play a role in the development of SAD in some people. Being deficient in vitamin D may trigger the onset of depression symptoms, possibly because of a connection to serotonin. One way in which people get vitamin D is through exposure to the sun. In the winter, when sunlight is low, there is a greater risk of deficiency.

In addition to these potential causes or contributing factors, there are several known risk factors for seasonal affective disorders. These include a family history of SAD or depression of another type, already having depression or bipolar disorder, and living far to the north or south of the equator where there is less winter sunlight.

Co-Occurring Disorders

As with other types of depression, a co-occurring substance use disorder is not uncommon with SAD. A person struggling with mood in the winter may turn to drugs or alcohol to self-medicate. Alternatively, misuse of substances can trigger or worsen feelings of depression, especially in the winter, contributing to the onset of SAD.

Being diagnosed with depression or bipolar disorder is also a risk factor for SAD, and these other mood disorders may co-occur. SAD can also trigger or contribute to other conditions and issues, such as suicidal thoughts, withdrawal from socializing, difficulties at work or in school, eating disorders, or anxiety disorders.

Treatment and Prognosis of Seasonal Affective Disorder

Seasonal affective disorder is treatable and the prognosis is largely positive. Most people who get diagnosed and seek treatment can find relief from seasonal symptoms. Treatment may include some of the strategies typically used for major depression: therapy and medications. Behavioral therapies can help patients learn to manage their symptoms, recognize and change negative thought patterns, and develop strategies for coping with the seasonal changes and mood shifts.

Medications for SAD include all types of antidepressants, but selective serotonin reuptake inhibitors are used most commonly. As with treating depression, it can take weeks to determine if a medication will work for an individual, and it may be necessary to try a few types to maximize the effect with minimal side effects. Because of this, a doctor may prescribe an antidepressant a few weeks before symptoms of SAD typically begin.

A unique treatment for SAD is light therapy. Because the low light of winter may be a trigger for SAD, being exposed to light can be helpful. Therapy involves the use of a device called a light box that mimics natural light. It is typically used first thing in the morning, for 30 to 60 minutes, to expose the patient to light after waking up and is used every day from fall to spring. Patients should be shown how to use the light box correctly by a medical or mental health professional before taking it home to use.

With professional mental health treatment and good self-care throughout the winter, the prognosis for managing SAD is good. Self-care may include keeping track of mood, eating well, getting exercise and adequate sleep, taking vitamin D supplements, and planning social activities. SAD is seasonal and comes and goes, but it is possible to find relief, even in the middle of winter.