Seasonal Affective Disorder: Causes and Treatment Options

Written by Rachel De La Merced and reviewed by Board Certified Psychiatric Nurse Practitioner Kate Filippelli, PMHNP who specializes in evidence-based psychiatry practices with personalized treatment plans for all mental health challenges, including psychiatric medication management, research-based supplements and behavioral interventions for major depressive disorder, bipolar disorder, anxiety, panic, OCD, ADHD and eating disorders.

 

Seasonal affective disorder (SAD) is a type of depression that follows a recurring seasonal pattern. For many people, symptoms begin during the fall or winter and improve during the spring and summer. Less commonly, depression can follow a spring or summer pattern. [1]

It is normal to experience changes in mood and energy throughout the year. However, SAD is more than simply feeling tired during the winter or disliking shorter days. When seasonal changes repeatedly cause significant changes in mood, sleep, appetite, energy, or daily functioning, it may be time to seek professional support.

In our clinical experience at Remedy Psychiatry, we often see patients initially attribute recurring seasonal changes in energy, motivation, or mood to their environment or lifestyle rather than recognizing them as a pattern of depression. Identifying when symptoms consistently emerge can be an important part of determining whether treatment may be helpful.

What Is Seasonal Affective Disorder?

Seasonal affective disorder is a form of depression associated with a predictable seasonal pattern. Symptoms typically occur during a particular season and improve during another part of the year. The most common pattern is winter-onset SAD, which tends to occur as daylight decreases. [1]

People with SAD can experience many of the same symptoms associated with other depressive disorders, including persistent sadness, loss of interest in activities, difficulty concentrating, low energy, and changes in sleep or appetite. [1, 2]

If you have ever wondered, “what does depression feel like when it happens every winter?”, the answer can vary. Some people primarily notice low mood and loss of interest, while others notice depression fatigue, increased sleep, social withdrawal, or difficulty getting motivated.

Because symptoms can develop gradually, it is possible to mistake SAD for stress, burnout, or simply having a difficult season. Recognizing a recurring pattern can be an important first step toward getting appropriate care.

What Causes Seasonal Affective Disorder?

The exact cause of SAD is not fully understood, but changes in daylight appear to play an important role. Reduced sunlight exposure during the fall and winter may affect the body’s circadian rhythm, which helps regulate sleep and other biological processes. Changes in light exposure may also affect systems involved in mood regulation. [1, 2]

This may help explain why depression and sleep can become closely connected during seasonal changes. Some people with winter-pattern SAD sleep considerably more than usual, while others experience disrupted sleep schedules. [1]

Researchers have also investigated the relationship between seasonal changes in light exposure, serotonin activity, melatonin, and the body’s internal clock. These biological changes may contribute to depressive symptoms in people who are particularly sensitive to changes in daylight. [1, 2]

However, SAD is not caused by a single factor. Genetics, individual biology, geographic location, previous depression, and other environmental factors may also influence someone’s risk. [2]

Signs And Symptoms Of Seasonal Affective Disorder

SAD can cause symptoms that affect both emotional and physical well-being. Common symptoms include:

• Persistent sadness or low mood
• Loss of interest or pleasure
• Low energy or depression fatigue
• Sleeping more than usual
• Difficulty sleeping
• Trouble concentrating
• Social withdrawal
• Feelings of hopelessness or worthlessness
• Changes in appetite
• Weight changes
• Increased cravings, particularly for carbohydrates
• Irritability
• Anxiety
• Difficulty completing everyday responsibilities

Winter-pattern SAD is particularly associated with oversleeping, increased appetite, carbohydrate cravings, weight gain, and pronounced fatigue. Summer-pattern SAD may involve insomnia, decreased appetite, weight loss, agitation, or anxiety. [1, 2]

Some people experience depression-related irritability rather than obvious sadness. They may become more impatient, frustrated, or short-tempered as their energy and mood change. Symptoms can also overlap with other mental health conditions. For example, someone may experience both SAD and an anxiety disorder, making it important to look at the full pattern of symptoms rather than focusing on one symptom alone.

Seasonal Affective Disorder Vs. Other Types Of Depression

Many people experience temporary changes in energy or motivation during the darker months. This is sometimes called the “winter blues,” but it is not necessarily the same as SAD.

One important difference is the severity and impact of symptoms. Someone experiencing a temporary dip in mood may still be able to maintain their normal responsibilities and relationships. SAD can cause more significant symptoms that interfere with work, school, relationships, self-care, or other areas of life. [1]

The distinction between depression vs burnout can also be important. Both can involve exhaustion, reduced motivation, and difficulty concentrating, but depression can affect multiple areas of a person’s life and may involve persistent changes in mood or loss of interest. A psychiatric provider can help determine what may be contributing to your symptoms.

A recurring seasonal pattern is an important part of evaluating SAD. If depressive symptoms occur throughout the year rather than primarily during a particular season, another depressive disorder may be more likely. [1, 2]

Other conditions can also resemble SAD. For example, persistent depressive disorder involves a more chronic pattern of depressive symptoms, while major depressive disorder can occur independently of the seasons. [3, 4]

How Is Seasonal Affective Disorder Diagnosed?

There is no single blood test or scan that can diagnose SAD. Instead, a psychiatric provider will typically evaluate your symptoms, their severity, when they occur, and how they affect your daily functioning. [1]

A provider may ask:

• When do your symptoms typically begin?
• When do they improve?
• Has the same pattern occurred in previous years?
• Do your symptoms improve during another season?
• How have your sleep and energy changed?
• Have you noticed changes in appetite or weight?
• Are you withdrawing from activities or relationships?
• Have you experienced depression outside of the seasonal period?

A provider may also screen for other conditions that can cause similar symptoms. This can include other depressive disorders, anxiety disorders, bipolar disorder, medical conditions, and medication-related effects.

A history of unusually elevated or energized moods is especially important to discuss because depressive episodes can occur as part of bipolar disorder, which requires a different treatment approach.

In our Remedy psychiatric practice, we place particular importance on distinguishing seasonal depression from bipolar depression and other causes of mood changes before recommending treatment. A careful history of past mood elevation, sleep changes, medication response, and symptom timing can meaningfully influence treatment decisions.

Seasonal Affective Disorder Treatment Options

There are several seasonal affective disorder treatment options. Depending on the severity and pattern of symptoms, treatment may include light therapy, psychotherapy, antidepressant medication, or a combination of approaches. [1, 5]

Light Therapy

Light therapy is one of the best-known treatments for winter-pattern SAD. It involves using a specialized bright-light box to provide exposure to artificial light during the darker months. A commonly recommended approach involves using a 10,000-lux light box for approximately 30-45 minutes in the morning, although treatment should be individualized with guidance from a healthcare professional. [1]

Research continues to examine how different types of visible light affect SAD. A 2025 systematic review and network meta-analysis found that visible-light therapy may be effective for SAD, although the researchers noted that additional high-quality research is needed. [6]

Light therapy is not appropriate for everyone. People with certain eye conditions or those taking medications that increase sensitivity to light may need additional guidance. Individuals with bipolar disorder should also discuss light therapy with a healthcare professional because mood elevation can be a potential concern. [1]

Psychotherapy

Psychotherapy can also be used to treat SAD. Cognitive behavioral therapy adapted specifically for SAD, known as CBT-SAD, focuses on changing unhelpful thoughts and behaviors associated with seasonal changes and increasing engagement in meaningful activities. [1, 7]

Research suggests that CBT-SAD and light therapy can both improve symptoms. Some research also suggests that the benefits of CBT-SAD may persist beyond the treatment period, potentially helping people manage recurring seasonal symptoms. [7, 8]

As a psychiatric nurse practitioner at Remedy Psychiatry, I often place importance on ensuring that patients have either pursued or are willing to pursue psychotherapy as part of their treatment plan. Combining psychotherapy with appropriate psychiatric management can provide more comprehensive care and support more meaningful, sustainable treatment outcomes.

Antidepressant Medication

Antidepressant medication may be appropriate for some people with SAD, particularly when symptoms are moderate to severe or significantly interfere with daily functioning. Medication may also be considered when someone has experienced recurring seasonal depressive episodes. [1, 5]

A psychiatric provider can consider your symptoms, medical history, previous response to medication, potential side effects, and whether symptoms occur only seasonally or throughout the year when determining whether medication may be appropriate.

Vitamin D

Vitamin D has also been studied in relation to SAD, particularly because vitamin D levels can be affected by reduced sunlight exposure. However, research on vitamin D as a treatment or preventive strategy for SAD has produced mixed results. It should not automatically be considered a replacement for established treatments such as light therapy, psychotherapy, or medication. [1, 9]

Can Seasonal Affective Disorder Go Away?

A common question is, “can depression go away?” With SAD, symptoms may improve as the season changes and daylight increases. However, that does not mean recurring seasonal depression should be ignored.

If the same symptoms return every year, become more severe, or interfere with your ability to function, seeking an evaluation can help you understand what is happening and identify appropriate treatment.

Knowing when to seek help for depression is particularly important if you are experiencing persistent hopelessness, significant social withdrawal, major changes in sleep or appetite, difficulty functioning, or thoughts of death or suicide. If you are experiencing thoughts of suicide or are in immediate danger, seek emergency help or call or text 988 in the United States.

Can Seasonal Affective Disorder Be Prevented?

For people who experience SAD at the same time each year, treatment may sometimes begin before or around the time symptoms typically appear. This is something to discuss with a healthcare professional based on your individual history. [1]

Keeping track of mood, sleep, energy, and other symptoms throughout the year can also help identify a seasonal pattern. If you notice that symptoms consistently appear during the same months, sharing that information with your psychiatric provider can make the evaluation more useful.

Healthy habits such as maintaining a regular sleep schedule, staying physically active, spending time outdoors when possible, and maintaining social connections may support overall mental wellness. However, these strategies should not replace professional treatment when depression is significant.

When To Seek Help For Seasonal Depression

You do not have to wait until your symptoms become severe to seek help. If changes in mood, sleep, energy, appetite, or motivation consistently occur during a particular season, consider talking with a psychiatric provider.

At Remedy Psychiatry, we often work with patients who have learned to anticipate a difficult season but have never received an individualized treatment plan for preventing or reducing those symptoms. Early evaluation can allow treatment strategies to be considered before seasonal symptoms become more disruptive.

SAD is a treatable form of depression, and identifying the seasonal pattern can help you and your provider develop a plan before symptoms become overwhelming.

If you find yourself asking “why am I always anxious?”, struggling with persistent fatigue, losing interest in activities you normally enjoy, or having difficulty maintaining your normal responsibilities during certain times of the year, an evaluation can help determine whether SAD or another mental health condition may be contributing to these changes.