You may be very well aware of the winter blues and have experienced some them to some degree, personally. This seasonal feeling is termed Seasonal Affective Disorder and it is a type of depression that most commonly affects people during winter months, particularly January and February. The reason it is termed seasonal is because for most individuals with this type of depression, it resolves by the Spring months when the weather begins to warm and the days become longer with more sunlight.  


The Science Behind Why Seasonal Affective Disorder Affects Mood:  

SAD has been linked to a biochemical imbalance in the brain prompted by shorter daylight hours and less sunlight in winter. As seasons change, people experience a shift in their biological internal clock or circadian rhythm that can cause them to be out of step with their daily schedule. SAD is more common in people living far from the equator where there are fewer daylight hours in the winter. 


Symptoms of SAD:  

SAD affects women more often than men, statistically and typically begins between 18-30 years of age. It’s important to note that if you feel any combination of these symptoms that you talk to your trusted healthcare provider or mental health professional as they can provide the most accurate diagnosis.  

  • Fatigue (regardless of number of hours of sleep) 
  • Weight gain often related to increase in carbohydrate cravings/intake  
  • Sad or particularly down mood 
  • Social withdrawal 
  • Lack of interest in typical activities 
  • Increase in physical ticks such as pacing or restless leg type behavior  
  • Feelings of guilt or helplessness/worthlessness 
  • Difficulty thinking, concentrating, or making decisions 
  • Thoughts of death or suicide  


Causes of SAD: 

Though there is much to Seasonal Affective Disorder that is still not fully understood by science, it is known that people who suffer from SAD have a common denominator: reduced activity of serotonin, a type of neurotransmitter in the brain that helps regulate mood.  

Sunlight also plays a role in that sunlight regulates the mechanism which helps sustain healthy serotonin levels. However, in people who suffer from SAD, this does not function as it should and levels of serotonin fall in the winter months. Sunlight also produces vitamin D and vitamin D is known to aid in serotonin activity. With decreased sunlight in the winter months, people with SAD may have lower Vitamin D levels if they are not consuming adequate amounts in their diet.  

Research also suggests that people with SAD overproduce another type of hormone called melatonin. Melatonin is responsible for making a person sleepy, contributing to the feelings of fatigue and excess sleep.  

Both serotonin and melatonin help maintain the body’s daily rhythm that is tied to the seasonal night-day cycle. In people with SAD, the changes in serotonin and melatonin levels disrupt the normal daily rhythms. As a result, they can no longer adjust to the seasonal changes in day length, leading to sleep, mood, and behavior changes. 


Treatment Options for SAD: 

Treatment is broken into four main categories: 

  • Vitamin D: have your provider check your vitamin D levels with a lab test, if your Vitamin D is low you may need to be treated with additional Vitamin D supplementation 
  • Light Therapy: this treatment involves sitting in front of a very bright light box (10,000 lux) every day for about 30-45 minutes, usually first thing in the morning, from fall to spring 
  • Antidepressants: two types of medication are approved — selective serotonin reuptake inhibitors (SSRIs) and bupropion 
  • Cognitive behavioral therapy (CBT): is a type of talk therapy aimed at helping people learn how to cope with difficult situations; CBT also has been adapted for people with seasonal affective disorder.  


Feeling your best year-round is possible. If you believe you’re experiencing symptoms of seasonal affective disorder, it is important to seek help to get to the root of the causes and find solutions that suit your needs.