Seasonal Affective Disorder (SAD)

Seasonal Affective Disorder (SAD) is defined by an experience of depressive symptoms in the fall and winter, when daylight is at a minimum (on rare occasions people experience the reverse, with depression in Spring and Summer).  According to the American Psychiatric Association, SAD is most common in January and February with about 5% of the US adult population experiencing it.  The DSM-5 does not list SAD as an diagnosis of its own, but rather as a subset within major depressive disorder, bipolar 1 and bipolar 2.

The website lists the DSM-5’s diagnostic criteria as:

  • A regular temporal relationship exists between the onset of mood symptoms and a particular time of year that is not better accounted for by seasonally related psychosocial stressors (e.g. seasonal unemployment, bereavement, trauma)
  • Full remission of mood symptoms (or change from depression to hypomania/mania), occurs at a regular time of year.
  • Over the last 2 years, at least 2 major depressive episodes have occurred that demonstrate the temporal seasonal pattern without evidence of non seasonal major depressive episodes occurring during the same period.
  • Over the lifetime course, the number of seasonal major depressive episodes substantially outnumbers nonseasonal major depressive episodes.

Not everyone who experiences a minor decrease in mood in the fall or winter has SAD.  For example, my mood often does worsen as the days shorten, however, my depressive episodes really tend to happen at any time of year.



In addition to talk therapy (particularly CBT) and medication (SSRI’s are the most common in this case), light therapy has been shown to be helpful.  Light therapy involves exposing yourself to a bright light from a light box each day. The duration and lux (or level of brightness) can vary depending on the manufacturer and/or doctor recommendation, however the general rule is 10,000 lux for 20-30 minutes a day.  When using a light box you should not look directly at the light, but it should be able to enter your eyes directly (so from the peripheral of your vision). A psychiatrist can help give more specific guidelines for your personal use of a lightbox.  For the most part, lightboxes are safe to use, and therefore they can be a good place to start.

Seasonal changes can be hard, if you think you are experiencing symptoms from the changing light and weather more severely than others, it’s a good idea to talk to your doctor to see if you may be experiencing SAD, and if so, what treatments to try.


  1. I have a consistent peak in depressive symptoms from approximately late August until late September most years, which I find a bit weird. It rains a lot in the winter where I live, and that can affect my emotional state but not necessarily my other depressive symptoms.


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