Seasonal Affective Disorder

Written By Lori Steffen

Seasonal Affective Disorder (SAD) is a type of depression that follows a seasonal pattern, most often showing up during the fall and winter months. Symptoms commonly peak in January and February, when daylight exposure is at its lowest.

SAD is a biological and neurological response to seasonal changes — not a weakness or lack of motivation.

Why does SAD happen?

Shorter days and reduced sunlight can affect the brain’s regulation of:

  • Circadian rhythms (sleep–wake cycles)

  • Serotonin (mood regulation)

  • Melatonin (sleep and energy levels)

  • Vitamin D levels

These changes can impact mood, energy, sleep, and focus.

Common signs of SAD

People with SAD may notice:

  • Low mood or emotional numbness

  • Fatigue or low energy

  • Sleeping more than usual or difficulty waking

  • Increased appetite, especially cravings for carbohydrates

  • Difficulty concentrating

  • Pulling back from social activities

To be diagnosed, these symptoms typically occur during the same season for two or more years in a row.

What helps?

SAD is very treatable. Evidence-based supports include:

  • Light therapy, usually used in the morning

  • Talk therapy, especially CBT

  • Medication, when appropriate

  • Vitamin D supplementation, if levels are low

  • Keeping a consistent sleep schedule

  • Spending time outdoors during daylight hours when possible

A reassuring note

Seasonal shifts in mood are common, and support can make a real difference. If winter feels heavier or harder than expected, you’re not doing anything wrong — your nervous system may simply need extra care during this season.

Lori Steffen