Seasonal Affective Disorder

Seasonal Affective Disorder

As we leave the bright days of summer behind and head into fall, some of us welcome the change in season. Leaves changing colors, cozy sweaters, and the refreshing crispness of the air can feel like an exciting new phase of life. However, for others, the shift toward darker, longer, and colder days are an unwelcome and anxiety-provoking transition.

Seasonal Affective Disorder (SAD) is a mood disorder that follows a cyclical pattern. Seasonal Affective Disorder affects approximately 5% of the population, while another 15% experience more mild versions of SAD. What sets SAD apart from depression is that the person experiencing SAD typically begins to experience symptoms — which are similar to those of depression —  in the fall and winter but feels relief from them during the spring and summer. Someone with depression may feel the symptoms regardless of the season.

What are the symptoms of SAD?

SAD can be debilitating and the symptoms can include: 

  • depressed mood
  • social withdrawal
  • lack of pleasure in activities
  • hopelessness
  • irritability
  • mental dysfunction
  • difficulty waking in the morning
  • daytime fatigue
  • carbohydrate cravings followed by weight gain
  • lack of energy 
  • suicidality

What causes SAD?

Although we do not fully understand the biology of SAD, we believe that a disturbance in circadian rhythms plays a role. Melatonin secretion takes place at night in low light. Scientists hypothesize that, in those with SAD, the longer period of melatonin secretion induces depression. Another hypothesis suggests that a phase shift in circadian rhythms is at least partially responsible for the development of symptoms.  With the later dawn and diminished light in winter circadian rhythms are delayed relative to the clock and sleep time. As some mammals respond to this change with hibernation, the SAD symptoms of hypersomnia, increased appetite, and weight gain may be a form of this response.

The retina responds to light and plays a major role in circadian rhythms. In the winter, the retina increases its sensitivity to light. It is thought that those with SAD may have an impairment of their retina, which causes the sensitivity to be diminished. 

How do you treat SAD?

There are effective means to treat SAD. The methods listed below are a combination of lifestyle practices you can begin at home and treatments by medical professionals. If you’re able to manage your symptoms at home, that’s wonderful. But if you begin to feel suicidal, or have other concerns about the symptoms you’re experiencing, please see your doctor right away.

Light therapy

  • Bright light therapy: Bright light therapy has been shown to be an effective treatment for SAD. It requires sitting in front of (16-30 inches away) a lightbox that emits white light using fluorescent bulbs at 10,000 lux.  Treatment should begin shortly after waking and last approximately 30 minutes.
  • Dawn Simulation: Dawn simulation therapy takes place during the last 30 to 90 minutes of sleep.  As opposed to the bright light used in bright light therapy dawn simulation uses a less intense light that gradually increases to room light level and coincides with the person’s normal waking time. This can be preferred as it doesn’t require making time to sit in front of the bright light in the morning. 

Outdoor activity

Getting outdoors daily, especially on bright days, is universally prescribed for those with SAD.


Research has shown that aerobic exercise can help to alleviate the symptoms of SAD.


Psychotherapy is an effective and important adjunctive treatment for SAD.  Gaining insight into thought patterns and developing a reframe or alternative perspective can shift some of the symptoms experienced by those with SAD.

Sleep Hygiene

Maintaining a regular sleep (light-dark) cycle is important.  Following the other aspects of good sleep hygiene in order to preserve restorative sleep is critical for patients with SAD.  

If you believe you may be experiencing the symptoms of SAD it is important to begin treating symptoms early. Make an appointment with your physician to discuss your symptoms and develop a personalized care plan so you can start feeling better soon.