Seasonal Affective Disorder

Reviewed by Jessica Muñoz, Jessica Muñoz is a registered nurse and educator with 20 years of experience in critical care emergency nursing, specializing in patient care, education, and evidence-based practice. She holds multiple certifications and serves as a Patient Safety Coordinator.

Seasonal affective disorder (SAD) is a type of depression linked to changing seasons. Often referred to as “winter depression,” the symptoms of SAD are typically more noticeable and severe in the winter, although some people may experience them during the summer instead.

Feeling a bit down during the colder months is somewhat common, and this milder version of SAD is known as the “winter blues.” In the USA, about 5% of adults suffer from seasonal affective disorder, with symptoms usually starting in early adulthood. SAD affects women more than men, with a ratio of 75:25.

Symptoms of SAD

SAD a type of depression that follows a seasonal pattern. Symptoms typically last 4 to 5 months each year and are similar to those of depression. While individuals with SAD may not experience all the symptoms, some common ones include:

• Persistent feelings of sadness
• Loss of interest in everyday activities
• Irritability
• Feelings of guilt, worthlessness, and despair
• Lethargy, sleepiness, and low energy throughout the day
• Difficulty waking up in the morning
• Cravings for sugary foods, overeating, and weight gain
• Disrupted sleep cycles
• Difficulty concentrating
• Suicidal thoughts
• Anxiety
• Loss of interest in social activities

Causes

The exact causes of seasonal affective disorder (SAD) are not fully understood. However, some hypotheses suggest that reduced exposure to sunlight during autumn and winter affects certain brain functions, leading to:

• Increased melatonin production: People with SAD have higher levels of melatonin, a hormone that induces sleepiness, making them feel lethargic, sleepy, and lazy throughout the day.
• Decreased serotonin production: Serotonin regulates mood, sleep, and appetite. Lower levels of this hormone in people with SAD lead to feelings of depression and anxiety.
• Disrupted circadian rhythm: Reduced sunlight can interfere with the body’s internal clock, disrupting essential functions like the sleep-wake cycle and potentially contributing to SAD.
• Negative thoughts: It’s unclear whether negative thoughts are a cause or effect of seasonal depression. However, people with SAD often experience negative thoughts, stress, and anxiety.

Additionally, genetics may play a role, as some cases of SAD run in families.

Risk Factors

Several factors can increase the risk of developing seasonal affective disorder (SAD):

• Family History: Individuals with SAD often have relatives who suffer from either SAD or other types of depression.
• Major Depression and Bipolar Disorder: Those with major depression or bipolar disorder may experience worsening symptoms seasonally if they have SAD.
• Distance from the Equator: People living far from the equator, especially near the poles, often suffer from SAD due to reduced sunlight in winter.
• Low Levels of Vitamin D: Vitamin D boosts serotonin activity, and its production depends on sunlight exposure. A lack of sunlight leads to decreased vitamin D levels, which can reduce serotonin activity.
• Region: Residents of higher latitudes or consistently cloudy regions are more likely to suffer from SAD.

Treatments

Following a diagnosis, healthcare providers tailor treatments based on individual symptoms. Some people may require a combination of treatments, including:

• Phototherapy: Bright light therapy involves sitting in front of a special lamp for 30 to 45 minutes, typically in the morning. This is a common treatment for SAD.
• Cognitive-Behavioral Therapy (CBT): CBT, or talk therapy, helps individuals cope with challenging situations through various activities. It is highly effective for treating SAD and produces long-lasting effects.
• Antidepressant Medication: Providers may recommend antidepressants to manage SAD, often in conjunction with light therapy.
• Spending Time Outdoors: Engaging in outdoor activities and increasing exposure to sunlight can help alleviate SAD symptoms.
• Taking Vitamin D Supplements: Vitamin D supplements can significantly reduce SAD symptoms.
• Lifestyle Adjustments: Regular exercise, increased sunlight exposure, and stress management are recommended to help mitigate SAD symptoms.

References

• Overview - Seasonal affective disorder (SAD) - NHS, 2024. https://www.nhs.uk/mental-health/conditions/seasonal-affective-disorder-sad/overview/
• Seasonal affective disorder (SAD) - Symptoms and causes - Mayo Clinic, 2019. https://www.mayoclinic.org/diseases-conditions/seasonal-affective-disorder/symptoms-causes/syc-20364651
• Seasonal Affective Disorder. NIMH.nih.gov. 2019. https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder