Seasonal Depression: Causes, Signs, and Treatments

Seasonal Affective Disorder (SAD) is a condition where changing seasons affect a person’s mood. Also known as seasonal depression, SAD usually begins in the fall and lasts until the spring. 

Depression onset by the seasons isn’t any less concerning than other types of depression. And while it is common, SAD is also treatable. Here’s a look at what seasonal depression is, what signs to watch for, and the best tips for treating it.

What is Seasonal Depression?

Seasonal depression is a physiological response to reduced sunlight during winter. People who live in more northern climates, where it’s colder and darker during the winter, are more prone to this condition. Research shows that the further a person lives from the equator, the more likely they are to struggle with seasonal depression (1). 

Seasonal depression varies in terms of severity, but not all forms of SAD are equal. For example, “the winter blues” is a more common and less severe response to winter. In fact, it’s normal to feel more tired and sluggish as the weather gets colder and the days get darker. Still, these symptoms don’t interfere with everyday life. These winter blues affect 14% of the US population.

Seasonal affective disorder is a more severe form of the condition. SAD correlates with Major Depressive Disorder (MDD). This means people with SAD experience similar symptoms, at a similar intensity, to MDD, including stress, anxiety, appetite changes, insomnia, and changes in interests (2). 

SAD affects 5% of the US population—most of whom live in northern climates. It usually manifests between the ages of 20 and 30, and it is more common among women (3). 

Seasonal affective disorder often begins in the fall, when the days get shorter and the nights get longer. The most notable marker for seasonal depression is daylight savings time. When most states set the clocks back in early November, the body experiences an environmental disruption. 

What Causes Seasonal Depression?

Seasonal depression occurs most often in the winter months. Most healthcare professionals and doctors agree that SAD is the body’s response to reduced light exposure. But why does less sunlight cause a person to feel sad? Winter affects a person’s mood because it disrupts the circadian rhythm and serotonin levels (4). 

Changes to Circadian Rhythm

The shorter, darker days of winter can affect a person’s circadian rhythms (their sleep-wake cycle). Circadian rhythm is primarily regulated by light and darkness; it’s why we feel sleepy at night and get up after the sun rises. Daylight is the main factor that regulates circadian rhythm (5).

Thehormone melatonin plays a primary role in regulating circadian rhythm. The brain releases melatonin in response to darkness, which helps us sleep through the night. When daylight comes, the brain stops releasing this hormone, which helps us feel energized. Research shows that the darkness of winter disrupts melatonin production, which plays a role in circadian rhythm disruption. 

Some people’s circadian rhythms are more sensitive to changes in daylight, altering their sleep-wake cycle. This can cause a person to feel tired and unmotivated during the day but feel restless during the night. Dysregulation in the circadian rhythm may also contribute to insomnia and sleep disturbances, making it harder to function in daily life.

Decreased Serotonin Levels

Serotonin is a neurotransmitter that regulates mood, among other functions, in the brain. Common antidepressants, such as Prozac, reduce symptoms of depression by increasing serotonin levels. These drugs are called Selective Serotonin Reuptake Inhibitors (SSRIs) because they help the brain retain serotonin, thereby decreasing symptoms of depression.

In people who don’t have seasonal affective disorder, serotonin levels remain steady throughout the seasons. This helps keep their mood regulated and, in response, promotes sustained motivation and positivity throughout the winter.

However, for those with seasonal affective disorder, serotonin levels drop during the winter (6). Low serotonin can affect the body in a range of ways, both physically and mentally. 

Common symptoms of low serotonin include (7):

• Insomnia
• Anxiety
• Depression
• Appetite changes
• Eating disorders
• Social anxiety

Reduced exposure to sunlight causes serotonin to drop, which leads to depression and other seasonal affective disorder symptoms.

Signs of Seasonal Depression

People with seasonal depression experience sadness in response to yearly changes in weather. For this reason, they tend to exhibit the same symptoms every year. These symptoms are similar to those experienced by people with major depressive disorder.

Common warning signs of SAD include:

• Waking up later in the day and moving more slowly
• Decreased energy levels
• Overeating
• Cravings for starches and sweets
• Rapid weight gain
• Decreased productivity and interest in activities

These symptoms can cause a person to experience low motivation, resulting in challenges at work and school. SAD can also interfere with interpersonal relationships (8). When a person feels unable to carry out their everyday life, the lack of control can become overwhelming. As a result,anxiety and stress tend to occur in tandem with seasonal depression.

How to Treat Seasonal Depression

There are a number of ways to treat seasonal depression. Still, different people are more responsive to certain therapies, so it’s important to try multiple options. Some of the most effective SAD treatments focus on regulating circadian rhythm, counteracting the sleep-wake cycle disturbances caused by winter.

Light Therapy

Since SAD is primarily a result of reduced sunlight exposure, light therapy can help improve the regulation of important bodily cycles. 

Light therapy involves using a lightbox to expose yourself to artificial light, which mimics the benefits of sunlight. Research shows that light therapy can not only treat SAD but prevent it from happening in susceptible individuals (9). 

The following criteria can increase the chances of light therapy success:

• A light with at least 10,000 LUX exposure (the sun has 50,0000)
• Absorption for a total of 30 minutes daily
• Use your lightbox before 10:00 am
• Don’t stare directly into the light

The artificial light that emanates from light therapy boxes mimic that of the sun, and they’re an effective way to prevent and treat seasonal depression (10). Lightboxes are also a healthy option because they minimize exposure to UV rays, which can be harmful to the skin. 

Exercise in Daylight

Exercise has long been shown to improve mood among people who experience depression. It doesn’t matter which type of exercise either: walking, running, weight training, and flexibility training have all been shown to reduce depression (11).

For people with seasonal affective disorder,exercising outdoors may be the key to elevating mood (12).

A walk or run outside in daylight hours can help a person reap the positive benefits of both exercise and sunlight. While this can be hard for people who work a typical 9-5 schedule in a northern location, even a short daily walk during lunch can have a positive effect.

Cognitive Behavioral Therapy

Cognitive Behavioral Therapy (CBT) is a psychotherapy method that may help alleviate the symptoms of SAD. A person using CBT may employ specific thinking patterns, such as replacing negative thoughts with positive thoughts.

CBT-SAD is a sub-type of CBT therapy specifically designed for people with seasonal depression. It can help a person identify and implement healthy coping mechanisms. For example, a CBT therapist may ask a person to consider which activities help them feel happy and energized. Then, the therapist and patient may work together to devise a plan for incorporating that activity more into daily life (13).

CBT coping techniques can also alleviate the anxiety that’s often associated with depression. For example, CBT can help a person become more aware of their anxious thoughts. Then, they can implement tools such as active problem-solving, in which they create a realistic plan for reducing the challenge at hand. 

Lastly, someone can reduce their mental health struggles by asking for help and delegating tasks to others. These healthy coping mechanisms put someone with SAD in more control of their life and its stressors, in turn reducing the overwhelm of winter (and the stress it brings).

In Summary

The darker, shorter days of winter impact everyone, especially those who live in northern climates. Yet, for people with seasonal affective disorder (SAD), winter has a significant impact on everyday life. People with seasonal affective disorder can experience a range of symptoms, including fatigue, weight gain, poor motivation, and insomnia.

Seasonal depression is closely tied to circadian rhythm, and both serotonin and melatonin play an essential role in how SAD manifests. Treatment for seasonal affective disorder is available. Light exposure remains the most effective way to regulate the body’s sleep-wake cycle and restore a balanced mood.

Michelle Polizzi - Contributing Writer, Physician’s Choice