Seasonal Affective Disorder (SAD): Symptoms, Causes, and Treatments

What Is Seasonal Affective Disorder?

Seasonal affective disorder (SAD) is a recurrent depressive episode that follows a seasonal pattern—most commonly starting in fall, continuing through winter, and remitting in spring. A less common summer-pattern SAD also exists.

Common Symptoms

• Persistent sad, hopeless, or “empty” mood most of the day
• Loss of interest in previously enjoyed activities
• Low energy, fatigue, or sluggishness
• Difficulty concentrating or making decisions
• Sleep changes (hypersomnia or insomnia)
• Appetite changes, often craving carbohydrates and weight gain
• Feelings of worthlessness or excessive guilt
• Recurrent thoughts of death or suicide

Proposed Causes

• Reduced daylight disrupting circadian rhythms
• Melatonin dysregulation affecting sleep-wake cycles
• Serotonin reduction linked to diminished sunlight
• Genetic predisposition and family history of mood disorders

Evidence-Based Treatments

• Light therapy: Daily exposure to 10,000 lux cool-white fluorescent light for 20–30 minutes each morning.
• Antidepressants: SSRIs (e.g., fluoxetine, sertraline) or bupropion XL for prevention.
• Psychotherapy: Cognitive-behavioral therapy (CBT) tailored for SAD.
• Lifestyle: Regular exercise, outdoor time, consistent sleep schedule, vitamin D supplementation if deficient.

Early recognition and treatment can markedly improve quality of life during vulnerable seasons.