Explained: What Is Seasonal Affective Disorder? Know Its Symptoms, Causes And Treatments

Seasonal affective disorder can affect how a person feels, thinks and performs everyday activities. Mostly, seasonal affective disorder starts in the late fall or early winter, and goes away in summer

Seasonal affective disorder is a type of depression which makes people feel sad or unsatisfied for short periods of time when the seasons change. The disorder comes and goes in a seasonal pattern, and hence, the name. Often, one may start feeling "down" when the days get shorter in the fall and winter, according to the United States (US) National Institutes of Health (NIH). Such periodic mood swings during winter are also known as "winter blues". Some people often start feeling better in the spring because there are longer daylight hours. 

Types of seasonal affective disorder

Seasonal affective disorder can affect how a person feels, thinks and performs everyday activities. Mostly, seasonal affective disorder starts in the late fall or early winter, and goes away during spring and summer. In most cases, the symptoms of seasonal affective disorder become more prominent and severe during winter. When one experiences mood swings during winter, it is called winter-pattern seasonal affective disorder or winter depression. When one experiences these depressive episodes during the spring or summer months, it is called summer-pattern seasonal affective disorder to summer depression. This is less common compared to winter depression.

What are the symptoms of seasonal affective disorder?

Seasonal affective disorder is a type of depression characterised by its recurrent seasonal pattern, with symptoms lasting about four to five months every year. The symptoms of this disorder are similar to those associated with major depression. The symptoms of major depression include feeling depressed most of the day as a result of change of season, experiencing changes in appetite or weight, persistent low mood, feeling agitated, irritability, feeling hopeless, worthless or guilty, having frequent thoughts of death or suicide, losing interest in activities, having trouble sleeping, having low energy, feeling lethargic having difficulty concentrating, and sleeping for longer than normal, among others.

The additional specific symptoms for winter-pattern seasonal affective disorder include oversleeping or hypersomnia, weight gain, overeating, craving for carbohydrates and social withdrawal.

The specific additional symptoms experienced by people suffering from summer-pattern seasonal affective disorder include trouble sleeping, restlessness and agitation, poor appetite, weight loss, anxiety and episodes of violent behaviour.

What are the causes of seasonal affective disorder?

While the exact cause behind seasonal affective disorder is not known, the episodes of depression often occur in winter due to low amounts of sunlight. 

Due to the lack of sunlight, a part of the brain called the hypothalamus might stop working properly. This affects the production of melatonin and serotonin, and also the body's internal clock or circadian rhythm. 

In people with seasonal affective disorder, melatonin, a hormone that makes one feel sleepy, may be produced in higher than normal levels inside the body. 

A lack of sunlight leads to lower levels of serotonin, a hormone that affects one's mood, appetite and sleep. Lower levels of serotonin are linked to depression. Serotonin is a neurotransmitter which regulates mood. 

Since the body uses sunlight to adjust timings for various important functions, such as waking up, lower light levels during winter may disrupt the body clock and lead to symptoms of seasonal affective disorder, according to the United Kingdom (UK) National Health Service (NHS). 

Both serotonin and melatonin help maintain the circadian rhythm that is tied to the seasonal night-day cycle. The normal daily rhythms get disrupted due to the changes in day length. This leads to sleep, behaviour and mood changes. 

Since Vitamin D is believed to promote serotonin activity, deficits in Vitamin D may aggravate these problems. The body produces vitamin D when exposed to sunlight. Therefore, low sunlight during winter results in lower vitamin D levels, hindering serotonin activity.

Genetic factors may also make one more susceptible to seasonal affective disorder. 

People with seasonal affective disorder experience negative thoughts and feelings about winter and its associated limitations. 

How can seasonal affective disorder be treated?

Seasonal affective disorder can be treated by taking lifestyle measures, through light therapy, talk therapy or psychotherapy, antidepressant medications, vitamin D.

Light therapy

Since the 1980s, light therapy has been used as a treatment for seasonal affective disorder. The therapy aims to expose people with the disorder to a bright light every day to make up for the diminished natural sunshine in winter. 

In order to undergo light therapy, a person must sit in front of a very bright light box, with a luminosity of 10,000 lux, every day, for about 30 to 50 minutes. They should ideally undergo light therapy in the morning, and from fall to spring. 

These light boxes are usually 20 times brighter than ordinary indoor light. They filter out potentially damaging ultraviolet light. This makes light therapy a safe treatment for most people. 

However, people with eye diseases or those taking certain medications that increase sensitivity to sunlight should avoid light therapy. 

Medications

Since seasonal affective disorder is a form of depression, and is associated with low levels of serotonin activity, one must take antidepressant medications prescribed by a licensed medical professional. These medications are called serotonin reuptake inhibitors (SSRIs). The agents enhance patients' moods. Some examples include fluoxetine, citalopram, sertraline, escitalopram, and paroxetine.

Bupropion is another type of antidepressant which the US Food and Drug Administration has stopped. It can prevent the recurrence of seasonal major depressive episodes when taken daily from fall to spring. 

Vitamin D

People with vitamin D deficiency can also experience seasonal affective disorder. They can consume vitamin D to be relieved of the symptoms.

Psychotherapy

Cognitive behavioural therapy is a type of talk therapy which can help people to learn how to cope with difficult situations, and has been adapted for people with seasonal affective disorder. Talk therapy or psychotherapy is conducted in two weekly group sessions for six weeks and focuses on replacing negative thoughts related to winter with more positive thoughts.