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Introduction

Seasonal affective disorder (SAD) consists of recurrent depression, mania, or hypomania that follows a seasonal pattern of onset and remission.  SAD is not a standalone diagnosis but rather a specifier of unipolar major depressive disorder (ie, MDD with seasonal pattern) and bipolar disorders (ie, bipolar II disorder with seasonal pattern).

The term SAD typically refers to unipolar depressive episodes with fall-winter onset and spring-summer remission since this is the most common pattern of symptoms; the remainder of this article pertains only to this subtype of SAD.

Epidemiology and risk factors

Among patients diagnosed with MDD, 10%-20% have SAD.  This condition is more common in young adults (usual onset occurs between age 20-30) and females.

Risk factors for SAD include:

  • Geographic location:  areas with less daylight in winter and more in the summer such as those in northern latitudes

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