What Is Seasonal Affective Disorder or SAD? Understanding Depression Through Seasonal Triggers

Seasonal Affective Disorder (SAD) is a form of depression that follows a specific seasonal pattern, typically surfacing in fall and winter. Beyond the transient stress that comes with winter holidays or summer vacation plans, SAD involves persistent and often severe symptoms that impact individuals for about four to five months each year ¹. In the United States, approximately 4% to 6% of people struggle with SAD, with an additional 10% to 20% experiencing milder forms ². It is frequently observed in northern regions with longer, harsher winters and reduced sunlight.

There are several treatments to improve symptoms of SAD and prevent them from worsening. Here’s a breakdown on the nuances of SAD, shedding light on seasonal patterns and offering insights to manage its impact on mental health.

What Is Seasonal Affective Disorder (SAD)?

SAD is a form of depression that happens during different seasons — primarily fall and winter — which impacts your mental health for about four to five months every year. These depressive symptoms must be present for two consecutive years in order to meet the clinical criteria for SAD under the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR) — criteria used by mental health professionals to diagnose mood disorders. Although the exact causes of SAD are not fully understood, factors such as sunlight, genetics, and neurotransmitters are believed to play a role in triggering depressive episodes.

Types of SAD

SAD is often categorized into two subtypes: winter-onset and summer-onset. Here’s what that looks like:

• Winter-pattern SAD (winter depression): Characterized by depression symptoms that occur in the fall and winter months for two consecutive years, potentially caused by reduced sunlight exposure, which can disrupt circadian rhythms and melatonin production.
• Summer-pattern SAD (summer depression): Characterized by symptoms of depression that occur in the summer and spring months, potentially caused by weather changes that trigger irritability and agitation. Summer-pattern SAD is less common than winter-pattern SAD.

SAD can develop in any part of the year regardless of season-related changes in climate, and each subtype can manifest differently, so recognizing symptoms and taking prompt action is critical to improve your quality of life during these months. 

SAD vs. the “holiday blues”

Most people experience SAD during the winter and fall months, which is why it is often confused with the “holiday blues.” However, the holiday blues refers to situational stress, sadness, and loneliness during the holidays, and symptoms will subside after a few days to a few weeks after the hustle and bustle of the holidays passes. Additionally, the holiday blues are not a mood disorder diagnosable by the DSM-5-TR.

What Is the Cause of SAD? 

The exact causes of SAD are not fully understood, but research suggests that there are several season-specific factors that may be responsible for triggering symptoms in those who are susceptible. Here are some potential causes of both winter-pattern SAD and summer-pattern SAD. 

Potential causes of winter-pattern SAD

Understanding the specific causes and triggers of winter depression can help you recognize symptoms early and seek appropriate treatment options to manage this seasonal condition.

Sunlight pattern fluctuations and sleep disruptions

Research suggests that the lack of sunlight during the winter and fall months can affect the body in ways that might contribute to SAD. Reduced sunlight exposure can cause vitamin D deficiency, disrupt to your circadian rhythm or biological clock, decrease serotonin levels, and cause an imbalance in melatonin — all of which can disrupt sleep patterns and trigger feelings of depression ¹.

Sunlight plays an important role in maintaining serotonin levels — a neurotransmitter that influences mood — and reduced natural light can potentially bring about depressive symptoms. Additionally, melatonin is a hormone that governs sleep quality, and vitamin D affects the part of the brain in charge of mood regulation, supporting your body’s breakdown of mood-related neurotransmitters like dopamine and noradrenaline. When there’s less sunlight, you may produce excessive melatonin and become vitamin D deficient.

Stress and anxiety relating to holiday celebrations

Navigating the winter holiday season proves challenging for many, stirring a mix of emotions and stressors. The ongoing stressors of trying to create a flawless holiday experience can compound with the financial constraints and social commitments of end-of-year celebrations, leading to feeling overwhelmed. 

According to research done in 2022, 31% of adults feel more stressed during the winter months compared to the previous year, with concerns about affordability particularly impacting younger adults and those with lower incomes ³. This statistic highlights the growing psychological distress surrounding the year-end months, as navigating workplace stress, balancing responsibilities, and striving for the perfect holiday experience foster a situation where stress contradicts the traditional expectations of cheer and merry.

These factors are potentially at the root of people experiencing increased emotional turmoil during the winter months, as a poll conducted by John Hopkins Medicine found that 41% of people say they are more stressed during the holidays ⁴. Therefore, it’s critical to recognize signs of SAD for effective management, which include prolonged feelings of sadness, loneliness, diminished interest in once-enjoyed activities, persistent anxiety, and sleep disturbances. Acknowledging and addressing these emotional challenges is essential for a sustained emotional wellbeing for a more fulfilling holiday experience.

End-of-year rumination

The march toward the end of the year can cause many to reflect and ruminate on their personal growth — or lack thereof — creating an environment for feelings of inadequacies to arise. You may find that as you reflect on your accomplishments, relationships, and unfulfilled resolutions, you begin to dwell on your unmet expectations, exacerbating symptoms of depression. To combat these feelings, it is important to practice mindfulness and minimize rumination during this vulnerable time.

Related: New Year Depression

Hormonal changes beyond melatonin

While research often focuses on melatonin and its relationship to SAD, your body’s seasonal changes can trigger a much wider hormone response. When winter brings less sunlight, your stress hormone patterns shift, thyroid function can decrease, and in women, estrogen levels may fluctuate seasonally — all of which affect your mood and energy. 

When one of these hormones is impacted by seasonal changes, the others follow suit. This provides a potential explanation as to why SAD isn’t just about feeling sleepy, and why you might experience changes in appetite, weight, energy levels, and emotional wellbeing as the seasons change.

Potential causes summer-pattern SAD

Although less common, it is crucial to understand what may potentially cause summer depression, especially when considering the summer months see the highest rates in suicide.

If you or a loved one is having thoughts about hurting themselves or others, call the Suicide and Crisis Lifeline immediately at 988.

Changes in heat and humidity

When the weather changes as spring and summer approaches, the heat and humidity that comes with it can lead to increased levels of irritability and agitation, which can trigger and exacerbate symptoms of SAD. Research suggests that increased stress levels associated with the extra effort it takes to regulate body temperature and keep cool may have a direct impact on mood regulation ⁵. Furthermore, high temperatures can interfere with your sleep quality as your bed may simply be too warm for comfort. 

Excessive sunlight exposure

Similar to how lack of sunlight exposure can disrupt circadian rhythms, too much sun can impact your sleep quality as your body responds by slowing the production of melatonin. This is of particular concern for those who are light sensitive, as prolonged daylight hours can lead to insomnia, mood changes, and other symptoms of SAD.

Inflammatory responses

For those with allergies, the spring and summer months are characterized by a spike in pollen count. As your body manages its allergic response, the stress placed on your immune system can create an inflammatory response that may contribute to depression ⁵.

Schedule disruptions

The summer months are often marked by vacations, school breaks, and disruptions in sleep schedules. Having a reliable routine can stave off feelings of anxiety and dread, and instability in your daily structure can create an environment where symptoms of depression are exacerbated. Additionally, medication efficacy, sleep quality, and consistent mindfulness practices all benefit from a consistent routine.

Related: Back to School Season and Mental Health

Beyond seasonality: additional causes of SAD 

Depression is rarely caused by one factor, and the same can be said of its subtype SAD. Although seasonal changes play a significant role, a history of mood disodrders, genetic predispositions, struggles with substance use, and stressful life events can also be considered causes of mental illnesses like depression. 

Who Is at Risk for SAD?

SAD doesn’t impact everyone the same way, and certain groups are more vulnerable, including:

• Women: SAD is diagnosed four times more frequently in women than in men ¹.
• Those who live from the equator: Living in more northern regions of the United States increases the risk of depression as these areas receive less sunlight during the fall and winter seasons.
• Those with a family history of mood disorders: Your chances of developing SAD or another type of depression are higher if you have family members who suffer from mood disorders, such as major depression or bipolar disorder.
• Those with pre-existing mood disorders: When you’re already struggling with a mental health condition, it can make you more susceptible to developing SAD. 
• Younger people: SAD and depression are more prevalent in younger adults, teenagers, and children. As you grow older, your vulnerability of developing depression decreases as your hormones stabilize and you learn healthy emotional regulation skills.
• Those with a Vitamin D deficiency: When you naturally have lower vitamin D levels, you’re more vulnerable to experiencing low mood, fatigue, and irritability. 
• Those with melatonin dysregulation: This is an imbalance in the production and release of melatonin in the body, which can lead to disrupted sleep cycles. Sleep and mental health are closely intertwined. 
• Those with difficult lifestyle circumstances: This includes working night shifts, a sedentary lifestyle, poor sleep habits, and living a high-stress life.

What Are the Symptoms of SAD?

Knowing what symptoms of depression are can help you find prompt treatment and put you on the path to better mental wellness sooner. Here’s what symptoms of winter SAD and summer SAD look like. 

Symptoms of winter-pattern SAD 

When you know how symptoms of winter-onset SAD can manifest, you can better prepare for the year-end months to navigate this difficult time. Symptoms of winter depression include:

• Increased appetite or weight gain.
• Headache or fatigue. 
• Sleeping more than usual, or hypersomnia.
• Low mood and difficulty concentrating.
• Fluctuating energy levels.
• Feelings of guilt, hopelessness, or irritability.
• Avoidance of social situations or self-isolation.
• Loss of interest in activities that were once enjoyed.

Symptoms of summer-pattern SAD

Summer-onset SAD has symptoms that often contrast those of winter-pattern SAD and include: 

• Loss of appetite.
• Dramatic and unintended weight loss.
• Insomnia or trouble sleeping due to excessive daylight hours.
• Increased irritability, anxiety, agitation, and restlessness.

While everyone experiences emotional ups and downs throughout the year, SAD symptoms tend to recur at the same time and impact daily functioning. Treatment requires specific strategies due to the disorder’s cyclical nature and how it affects individuals during specific seasons. While SAD tends to impact individuals for four to five months each year, treatment often continues beyond that time frame and some people need continued support to manage their symptoms.

Related: What Is Holiday Depression?

Seasonal Affective Disorder Treatment Options

Navigating treatment for SAD involves collaborating with healthcare professionals to explore various approaches to manage symptoms effectively. From depression therapy and medications to innovative approaches like transcranial magnetic stimulation (TMS) therapy, individuals have diverse options to tailor their treatment plans based on personal preferences and needs.

Light therapy for seasonal depression

Bright light therapy involves exposure to very bright light — particularly blue light — to regulate melatonin and serotonin levels, which can positively impact mood ⁶. Since the 1980s, light therapy has been a primary treatment for winter-pattern SAD. During light therapy sessions, you’ll be exposed to a bright light box for about 30 to 45 minutes daily, typically in the morning during the fall and spring months. This type of therapy can compensate for the reduced natural sunlight experienced during darker months and filters out potentially harmful UV light, making it a safe treatment for most individuals ⁷.

Vitamin D supplementation

Taking vitamin D addresses deficiencies related to sunlight exposure and can support overall physical and mental health. This is especially helpful for winter-pattern SAD, where vitamin D deficiency is a potential cause.

Medications for depression

Depression can be managed with medication, pending a psychiatrist’s approval, and include: 

• Antidepressants are medications that can help alleviate symptoms of depression by affecting neurotransmitters in the brain. There are several types of antidepressant medications, but selective serotonin reuptake inhibitors (SSRIs) in particular have been proven effective in managing SAD symptoms, especially when combined with psychotherapy. 
• Hormonal therapy involves hormonal treatments to address imbalances, which can positively impact circadian rhythms and mood.

Related: Side Effects of Antidepressants

Psychotherapy

Psychotherapy, also known as talk therapy or counseling, is a beneficial intervention for individuals dealing with SAD. By imparting new ways of thinking and behaving, talk therapy aims to break the habits contributing to depression.

Cognitive behavioral therapy (CBT) — tailored for SAD as CBT-SAD — stands out as a focused psychotherapeutic approach. This method targets negative beliefs and thoughts associated with seasonal changes and replaces them with more positive ones. A structured CBT-SAD program typically spans two weekly group sessions over six weeks, incorporating behavioral activation exercises. These sessions help participants identify and schedule enjoyable season-appropriate activities, offsetting the loss of interest commonly experienced during challenging winter or summer months.

Transcranial magnetic stimulation (TMS) therapy

TMS therapy is FDA-approved for the treatment of depression and offers a promising path to recovering from depression, especially those with treatment-resistant depression (TRD). In a four-year follow up study published by the National Library of Medicine on people who are not taking medication and have TRD, around 50% of individuals responded positively to treatment ⁸. 

Lifestyle and holistic treatments

Some lifestyle changes and holistic treatments can be beneficial to managing SAD, including: 

• Dietary modifications: Changes in diet, potentially with a focus on foods that are high in vitamin D, can address deficiencies related to sunlight exposure.
• Increased exercises: Regular physical activity boosts dopamine levels and improves overall well-being to improve SAD symptoms. If the winter months make it difficult to exercise outside, consider home workouts or joining an indoor gym, if feasible.
• Meditation: Mindfulness practices can help develop healthy coping strategies for stress related to SAD.
• Improved sleep hygiene: Establishing good sleep habits and patterns can support the fatigue often associated with SAD.
• Dawn stimulation: Exposure to light — particularly in the morning — can regulate circadian rhythms and improve mood.

When To Seek Professional Help for SAD

If you are noticing your SAD symptoms becoming increasingly difficult to manage, seeking professional support can ease the duress experienced during this time of the season. You’ll be compassionately taught to properly manage symptoms that arise and learn real life coping techniques. If needed, medication and TMS therapy can be discussed and considered for your treatment plan as well. SAD doesn’t have to dictate your season — learn how to cope and alleviate your symptoms for easier transitions throughout the year. 

How Neuro Wellness Spa Can Treat SAD and Support Mental Wellbeing Throughout the Year

Dealing with mental health challenges like SAD involves recognizing patterns and individual triggers. The holiday season may bring stress, but prioritizing self-care and seeking support can make a profound difference. 

Neuro Wellness Spa offers a wide range of mental health treatment options designed to help you manage seasonal depression. Our psychiatrists can work with you to find the right psychiatric medication or to determine if TMS therapy is the right fit for you. Our care team can also work with you to provide psychoeducation on how your SAD is manifesting and how to implement routines. Additionally, we provide CBT, dialectical behavior therapy (DBT), and other therapeutic modalities that facilitate a supportive environment to discuss your seasonal depression concerns.

Take control of your well-being by contacting Neuro Wellness Spa today and learn more about how we can support you.

References

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2. Seasonal affective disorder. (2000, March 1). AAFP. https://www.aafp.org/pubs/afp/issues/2000/0301/p1531.html

3. As holiday season begins, America’s stress rises, but less about COVID-19. (n.d.). https://www.psychiatry.org/News-room/News-Releases/As-Holiday-Season-Begins-Americas-Stress-Rises

4. Martinez, M. (2022, December 5). ’Tis the season to focus on your mental health. Johns Hopkins Medicine. https://www.hopkinsmedicine.org/news/newsroom/news-releases/2022/12/tis-the-season-to-focus-on-your-mental-health

5. Sima, R. (2023, July 20). Sad in the summer? You may have summer seasonal depression. The Washington Post. https://www.washingtonpost.com/wellness/2023/07/03/summer-sad-depression-symptoms-causes-treatment/

6. Munir, S., Gunturu, S., & Abbas, M. (2024, April 20). Seasonal affective disorder. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK568745/

7. National Institute of Mental Health. Seasonal Affective Disorder. https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder/index.shtml

8. Mantovani, A., Pavlicova, M., Avery, D., Nahas, Z., McDonald, W. M., Wajdik, C. D., Holtzheimer, P. E., George, M. S., Sackeim, H. A., & Lisanby, S. H. (2012). LONG-TERM EFFICACY OF REPEATED DAILY PREFRONTAL TRANSCRANIAL MAGNETIC STIMULATION (TMS) IN TREATMNT-RESISTANT DEPRESSION. Depression and Anxiety, 29(10), 883–890. https://doi.org/10.1002/da.21967