Seasonal Affective Disorder

SAD Basics - Sunny Day Blues

• Definition: Recurrent Major Depressive Disorder (MDD) exhibiting a regular seasonal pattern of onset and remission.
• Subtypes:
  • Winter-pattern (most common): Fall/winter onset. Atypical symptoms: hypersomnia, overeating, weight gain, carbohydrate craving.
  • Summer-pattern (less common): Spring/summer onset. Symptoms: insomnia, poor appetite, weight loss, agitation.
• Epidemiology:
  • Prevalence: 1-10%, varies by geography (e.g., higher in Alaska vs. Florida).
  • Age of onset: Typically 20-30 years.
  • Gender: More common in women (♀:♂ ≈ 4:1).
• Key Risk Factors:
  • Family history of SAD or other mood disorders.
  • Living at higher latitudes (reduced sunlight exposure).

⭐ SAD prevalence increases with distance from the equator.

Pathophysiology - The Gloom Creators

• Melatonin Dysregulation:
  • Phase-delay theory: Melatonin release delayed in winter, causing circadian misalignment with sleep/wake cycle.
  • Altered total melatonin secretion.
• Serotonin (5-HT) Pathway Changes:
  • ↓ Brain serotonin levels or transporter (SERT) activity, especially in winter.
  • SERT gene polymorphism (e.g., 5-HTTLPR) associated with vulnerability.
• Vitamin D Deficiency:
  • Reduced sunlight exposure leads to ↓ Vitamin D, impacting serotonin synthesis and mood regulation.
• Genetic Factors:
  • Significant heritability; polymorphisms in genes related to circadian rhythms and serotonin pathways.
• Neurotransmitter Imbalances:
  • Dopamine and norepinephrine systems may also be dysregulated.

📌 Mnemonic: 'SAD M&Ms': Serotonin, Melatonin, Morning light.

⭐ The phase-delay hypothesis of melatonin secretion is a key theory in winter-pattern SAD.

Clinical & Diagnosis - Seasonal Signs

DSM-5 Criteria (MDD with Seasonal Pattern):

• Regular temporal link: MDE onset & full remission at predictable times of year (e.g., fall onset, spring remission).
• Minimum 2 years: Two such MDEs in consecutive years, no non-seasonal MDEs during this period.
• Seasonal MDEs significantly outnumber any non-seasonal MDEs over lifetime.

⭐ Atypical depressive symptoms like carbohydrate craving and hypersomnia are characteristic of winter-pattern SAD.

Symptom Patterns:

• MDD (non-seasonal)
• Bipolar disorder
• Hypothyroidism
• Chronic fatigue syndrome
• Vitamin D deficiency

Management - Sunshine Strategies

• Light Therapy (Phototherapy): First-line for winter SAD.
  • Standard regimen: 10,000 lux exposure for 30 minutes daily, ideally in the morning.
  • Mechanism: Corrects circadian phase delay.
  • Side effects: Generally mild; may include eyestrain, headache, nausea, or insomnia.
• Pharmacotherapy:
  • SSRIs (e.g., fluoxetine, sertraline): Effective for SAD symptoms.
  • Bupropion XL: Can be initiated prophylactically before autumn.
• Psychotherapy:
  • Cognitive Behavioral Therapy for SAD (CBT-SAD): Specifically adapted, as effective as light therapy.
• Lifestyle Modifications:
  • Regular physical exercise.
  • Maximize natural sunlight exposure.
  • Vitamin D supplementation if deficiency is present.
  • Maintain good sleep hygiene.

⭐ Morning light therapy is the cornerstone of treatment for winter SAD, aiming to correct the circadian phase delay.

High-Yield Points - ⚡ Biggest Takeaways

• Seasonal Pattern: Recurrent depression, typically winter onset and spring/summer remission.
• DSM-5 Criteria: At least two years of seasonal episodes, outnumbering non-seasonal ones.
• Atypical Symptoms: Common, including hypersomnia, ↑ appetite/weight gain, and carbohydrate craving.
• Pathophysiology: Involves melatonin dysregulation, serotonin dysregulation, and circadian rhythm shifts.
• First-line Treatment: Light therapy (phototherapy).
• Pharmacotherapy: SSRIs (e.g., fluoxetine) and bupropion are also effective options.
• Geography: More prevalent at higher latitudes due to reduced sunlight.