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Seasonal Affective Disorder

Learn everything you need to know about seasonal affective disorder (SAD), a type of depression that occurs during certain seasons. Find out how to cope with SAD and improve your mood and well-being.

Seasonal Affective Disorder

Seasonal affective disorder (SAD) is a type of mood disorder that affects millions of people around the world. It is characterized by recurrent episodes of depression that occur during certain seasons, usually winter or summer. SAD can interfere with your daily functioning, your relationships, your self-esteem and your quality of life.

But there is hope! SAD can be treated effectively with various strategies, such as light therapy, medication, psychotherapy and self-care. In this article, I will explain what SAD is, what causes it, what are the symptoms, how it is diagnosed, how it is treated and how you can manage it.

What is Seasonal Affective Disorder?

Seasonal affective disorder (SAD) is a subtype of major depressive disorder that follows a seasonal pattern. This means that people who have SAD experience depressive symptoms at the same time each year, usually during the fall or winter months in the Northern Hemisphere, or during the spring or summer months in the Southern Hemisphere. These symptoms often resolve during the opposite seasons.

SAD is sometimes called the “winter blues” or “summer depression”, depending on the season when it occurs. However, these terms may not capture the severity of the condition, which can be debilitating for some people.

SAD affects about 1 to 3 percent of the general population, and is more common among women than men. It is also more prevalent in higher latitudes, where there are fewer daylight hours during winter or more intense sunlight during summer.

What causes Seasonal Affective Disorder?

The exact cause of SAD is not fully understood, but several factors may contribute to its development. Some of these factors include:

  • Biological clock (circadian rhythm): Your circadian rhythm is your internal clock that regulates your sleep-wake cycle, hormone levels, body temperature, and other physiological functions. It is influenced by external cues, such as sunlight and temperature. When there are changes in the amount or intensity of daylight due to seasonal variations, your circadian rhythm may get disrupted, leading to changes in your mood and energy levels.
  • Brain chemistry: Your brain produces and uses certain chemicals called neurotransmitters to communicate with other parts of your nervous system. One of these neurotransmitters is serotonin, which is involved in regulating your mood, appetite, sleep, and other functions. Serotonin levels may decrease during winter due to reduced exposure to sunlight, which may trigger depressive symptoms. Another neurotransmitter that may play a role in SAD is melatonin, which is responsible for regulating your sleep cycle. Melatonin levels may increase during winter due to longer nights, which may affect your sleep quality and mood.
  • Vitamin D levels: Vitamin D is a hormone that is produced by your skin when it is exposed to sunlight. It helps your body absorb calcium and phosphorus, which are essential for bone health. It also has other functions in your immune system, brain, and other organs. Vitamin D deficiency may occur during winter due to reduced sun exposure, which may contribute to depression and other health problems.
  • Genetic factors: Some people may have a genetic predisposition to develop SAD or other mood disorders. If you have a family history of depression or SAD, you may be more likely to experience it yourself.
  • Personal factors: Your personality traits, coping skills, stress levels, social support, and life events may also influence your vulnerability to SAD. For example, if you are prone to negative thinking patterns, have low self-esteem, face significant stressors, or lack meaningful social connections, you may be more susceptible to developing SAD.

What are the symptoms of Seasonal Affective Disorder?

The symptoms of SAD vary from person to person, but they typically include:

  • Feeling sad, hopeless, or worthless most of the day
  • Losing interest or pleasure in activities you used to enjoy
  • Having low energy or feeling fatigued
  • Having difficulty sleeping or sleeping too much
  • Experiencing changes in your appetite or weight
  • Craving carbohydrates or sugary foods
  • Having trouble concentrating or making decisions
  • Feeling irritable or anxious
  • Having thoughts of death or suicide

The symptoms of SAD may differ depending on the season when they occur. For example:

  • Winter-onset SAD: This is the most common form of SAD that affects people during the fall or winter months. The symptoms may include oversleeping, overeating, weight gain and low energy.
  • Summer-onset SAD: This is a less common form of SAD that affects people during the spring or summer months. The symptoms may include insomnia, poor appetite, weight loss, agitation, and irritability.

Some people may also experience mixed episodes of SAD, where they have symptoms of both winter and summer depression, or rapid cycling, where they switch between depressive and manic or hypomanic episodes.

How is Seasonal Affective Disorder diagnosed?

There is no specific test to diagnose SAD, but your health care provider may use several methods to assess your condition, such as:

  • Medical history: Your health care provider will ask you about your symptoms, their duration, their severity, and their impact on your daily functioning. They will also ask you about your personal and family history of depression or other mental health conditions, your medication use, your substance use and your physical health.
  • Psychological evaluation: Your health care provider may use standardized questionnaires or interviews to evaluate your mood, thoughts, behaviour, and personality. They may also screen you for other mental health disorders that may co-occur with SAD, such as bipolar disorder, anxiety disorders, or substance use disorders.
  • Physical examination: Your health care provider may perform a physical examination to check for any signs of medical problems that may cause or worsen your symptoms, such as thyroid disorders, anaemia, or vitamin deficiencies.
  • Blood tests: Your health care provider may order blood tests to measure your hormone levels, such as thyroid hormones, cortisol, and melatonin. They may also check your vitamin D levels and other indicators of your general health.
  • Diagnostic criteria: Your health care provider will compare your symptoms and history with the diagnostic criteria for SAD that are established by the American Psychiatric Association in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). According to the DSM-5, you must meet the following criteria to be diagnosed with SAD:
    • You have a history of major depressive episodes that occur during a specific season (usually winter or summer) and remit during the opposite season.
    • The seasonal depressive episodes are more frequent than any non-seasonal depressive episodes in your lifetime.
    • The seasonal depressive episodes are not better explained by other factors, such as seasonal stressors, social rhythms, or substance use.

How is Seasonal Affective Disorder treated?

The treatment of SAD depends on the severity of your symptoms, your preferences, and your response to different interventions. The main treatment options for SAD include:

  • Light therapy: This is the first-line treatment for winter-onset SAD. It involves exposing yourself to a bright artificial light source for a certain amount of time each day, usually in the morning. The light mimics natural sunlight and helps regulate your circadian rhythm and brain chemistry. Light therapy devices are available in different forms, such as lamps, boxes, or visors. You can use them at home or at work under the guidance of your health care provider. Light therapy is generally safe and effective, but it may cause some side effects, such as eye strain, headache, or nausea. You should consult with your health care provider before starting light therapy if you have any eye problems, skin conditions, or mood disorders that may affect your sensitivity to light.
  • Medication: This is another common treatment option for SAD. It involves taking antidepressant drugs that help balance your brain chemistry and improve your mood. The most commonly prescribed antidepressants for SAD are selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (Prozac), sertraline (Zoloft) or paroxetine (Paxil). Another antidepressant that is approved by the Food and Drug Administration (FDA) for treating SAD is bupropion (Wellbutrin), which works by increasing the levels of dopamine and norepinephrine in your brain. Antidepressants may take several weeks to show their full effects, so you should not stop taking them abruptly or without consulting with your health care provider. Antidepressants may also cause some side effects, such as nausea, insomnia, weight changes, or sexual dysfunction. You should inform your health care provider about any side effects you experience or any other medications you are taking that may interact with antidepressants.
  • Psychotherapy: Psychotherapy is a type of talk therapy that helps you cope with your negative thoughts and feelings, identify and change unhelpful behaviour patterns, improve your self-esteem, and enhance your social skills. Psychotherapy can be done individually or in a group setting with other people who have SAD. The most effective form of psychotherapy for SAD is cognitive-behavioural therapy (CBT), which teaches you how to challenge and modify distorted thinking patterns that contribute to depression. CBT can also help you develop a regular schedule of activities that expose you to natural light and increase your physical activity and social interaction. Psychotherapy can be combined with light therapy or medication for optimal results.
  • Self-care: This involves taking care of yourself physically and emotionally by adopting healthy habits that support your well-being. Some self-care strategies for managing SAD include:
    • Keeping a regular sleep schedule and avoiding oversleeping
    • Eating a balanced diet and avoiding excessive intake of carbohydrates or alcohol
    • Exercising regularly and spending time outdoors when possible
    • Engaging in enjoyable and meaningful activities that boost your mood and self-esteem
    • Seeking social support from your family, friends, or other people who have SAD
    • Practicing relaxation techniques, such as meditation, Yoga, or breathing exercises
    • Seeking professional help if your symptoms are severe or interfere with your daily functioning

How can you prevent Seasonal Affective Disorder?

There is no sure way to prevent SAD, but you can take some steps to reduce your risk or minimize its impact on your life. Some of these steps include:

  • Starting treatment early, as soon as you notice the first signs of SAD
  • Continuing treatment throughout the season, even if you feel better
  • Following your health care provider’s recommendations and monitoring your response to treatment
  • Being aware of the triggers and warning signs of SAD, such as changes in your mood, energy, sleep, or appetite
  • Planning ahead for the seasons that affect you, such as scheduling vacations, activities, or events that give you something to look forward to
  • Educating yourself and others about SAD and its treatment options


Seasonal affective disorder is a common and treatable condition that affects many people around the world. It can cause significant distress and impairment in your personal and professional life, but it can also be managed effectively with various strategies, such as light therapy, medication, psychotherapy, and self-care. If you think you have SAD or know someone who does, do not hesitate to seek help from a qualified health care provider. You are not alone, and there is hope for recovery.

Please note that this article is for informational and educational purposes only and does not constitute medical advice or diagnosis.

If you are or someone you know is experiencing mental health issues, I strongly encourage you to seek help. Please contact your GP or mental health provider today.

There is no shame in seeking help for your mental health and well-being. You are not alone, and you deserve to feel better.