Seasonal Affective Disorder: More Than Just the Winter Blues

From the National Institute of Mental Health

What is seasonal affective disorder (SAD)? 

Many people go through short periods of time where they feel sad or not like their usual selves. Sometimes, these mood changes begin and end when the seasons change. People may start to feel “down” when the days get shorter in the fall and winter (also called “winter blues”) and begin to feel better in the spring, with longer daylight hours. 

In some cases, these mood changes are more serious and can affect how a person feels, thinks, and handles daily activities. If you have noticed significant changes in your mood and behavior whenever the seasons change, you may be suffering from seasonal affective disorder (SAD), a type of depression. 

In most cases, SAD symptoms start in the late fall or early winter and go away during the spring and summer; this is known as winter-pattern SAD or winter depression. Some people may experience depressive episodes during the spring and summer months; this is called summer-pattern SAD or summer depression and is less common.

What are the signs and symptoms of SAD? 

SAD is not considered a separate disorder but is a type of depression characterized by its recurrent seasonal pattern, with symptoms lasting about 4 to 5 months per year. Therefore, the signs and symptoms of SAD include those associated with major depression, and some specific symptoms that differ for winter-pattern and summer-pattern SAD. Not every person with SAD will experience all of the symptoms listed below. 

• Symptoms of major depression may include: 
  • Feeling depressed most of the day, nearly every day 
  • Losing interest in activities you once enjoyed 
  • Experiencing changes in appetite or weight 
  • Having problems with sleep 
  • Feeling sluggish or agitated 
  • Having low energy 
  • Feeling hopeless or worthless 
  • Having difficulty concentrating 
  • Having frequent thoughts of death or suicide 

• For winter-pattern SAD, additional specific symptoms may include: 
  • Oversleeping (hypersomnia) 
  • Overeating, particularly with a craving for carbohydrates 
  • Weight gain  
  • Social withdrawal (feeling like “hibernating”) 

• Specific symptoms for summer-pattern SAD may include: 
  • Trouble sleeping (insomnia) 
  • Poor appetite, leading to weight loss 
  • Restlessness and agitation 
  • Anxiety 
  • Episodes of violent behavior

How is SAD diagnosed? 

If you think you may be suffering from SAD, talk to your health care provider or a mental health specialist about your concerns. They may have you fill out specific questionnaires to determine if your symptoms meet the criteria for SAD.

What causes SAD? 

Scientists do not fully understand what causes SAD. Research indicates that people with SAD may have reduced activity of the brain chemical (neurotransmitter) serotonin, which helps regulate mood. Research also suggests that sunlight controls the levels of molecules that help maintain normal serotonin levels, but in people with SAD, this regulation does not function properly, resulting in decreased serotonin levels in the winter. 

Other findings suggest that people with SAD produce too much melatonin—a hormone that is central for maintaining the normal sleep-wake cycle. Overproduction of melatonin can increase sleepiness. 

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. 

Deficits in vitamin D may exacerbate these problems because vitamin D is believed to promote serotonin activity. In addition to vitamin D consumed with diet, the body produces vitamin D when exposed to sunlight on the skin. With less daylight in the winter, people with SAD may have lower vitamin D levels, which may further hinder serotonin activity. 

Negative thoughts and feelings about the winter and its associated limitations and stresses are common among people with SAD (as well as others). It is unclear whether these are “causes” or “effects” of the mood disorder, but they can be a useful focus of treatment.

How is SAD treated? 

Treatments are available that can help many people with SAD. They fall into four main categories that may be used alone or in combination: 

● Light therapy 

● Psychotherapy 

● Antidepressant medications 

● Vitamin D

Talk to your health care provider about which treatment, or combination of treatments, is best for you.

Can SAD be prevented? 

Because the timing of the onset of winter pattern-SAD is so predictable, people with a history of SAD might benefit from starting the treatments mentioned above before the fall to help prevent or reduce the depression. To date, very few studies have investigated this question, and existing studies have found no convincing evidence that starting light therapy or psychotherapy ahead of time could prevent the onset of depression. Only preventive treatment with the antidepressant bupropion prevented SAD in study participants, but it also had a higher risk of side effects. Therefore, people with SAD should discuss with their health care providers if they want to initiate treatment early to prevent depressive episodes.

Get Immediate Help 

If you or someone you know is in immediate distress or is thinking about hurting themselves, call the National Suicide Prevention Lifeline toll-free at 1-800-273-TALK (8255) or the toll-free TTY number at 1-800-799-4TTY (4889). 

You also can text the Crisis Text Line (HELLO to 741741) or go to the National Suicide Prevention Lifeline website at https://suicidepreventionlifeline.org.