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Diagnosing Depressive Disorders
Seasonal Affective Disorder (SAD)
winter

As one of the clinical subtypes of depression, seasonal affective disorder meets the criteria for major depression with a distinct pattern of onset, usually in winter. As SAD is associated with lower and briefer daytime light levels, it is more common in the northern hemispheres. Women suffer from SAD 4 times more often than men. Depressive symptoms typically start in late autumn or early winter, and characteristically improve (with or without treatment) in the spring or summer. In between, patients may function normally, although they can become hypomanic or manic in the summertime.


By definition, SAD is a recurrent disorder and patients must have had at least two episodes which met the DSM-IV criteria for major depressive disorder as well as the following criteria:

• onset and remission of episodes must occur regularly in the same seasons
• the last two seasonal episodes must be in consecutive years
• seasonal episodes must greatly outnumber any nonseasonal episodes
• no nonseasonal episodes in the last two episodes
• seasonal psychosocial stressors are excluded

 

SAD patients are also prone to a distinct set of vegetative depressive symptoms, including:

• an increased need for sleep
• carbohydrate cravings
• weight gain during their depressive episodes

 

 

Typically, somatic features including:

• fatigue
• low energy
• headache
• other pain syndromes prevail, and patients may say they feel as if they have a prolonged case of influenza
• immune function may be lowered

 

 

SAD patients also tend to feel almost immediately better on going south, to warmer, sunnier climates. Overall, SAD patients are less severely affected than patients with a major depressive illness and they are less likely to attempt suicide than those with major depression. Indeed, SAD patients often continue to work and function; that said, function is usually impaired and patients are clearly not living up to their full potential.

Please see:

Section II: "Managing Major Depression Disorder"
CANMAT – Guidelines for the Diagnosis and Pharmacological Treatment of Depression
(1st Edition Rev., 1999)
P. 22

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Over one million Canadians suffer from some form of depressive illness.