Seasonal affective disorder

Seasonal affective disorder is a pattern of depressive episodes that recur at particular times of year, most often in autumn and winter, with remission during other seasons.

Circadian rhythm: An approximately 24-hour cycle in biological processes, coordinated by internal clocks and environmental cues. Short winter days can shift biological timing in ways associated with seasonal symptoms.
Bright light therapy: A treatment that uses timed exposure to bright artificial light to address certain mood and circadian disorders. It is a commonly used treatment intended to compensate for reduced winter daylight.
Major depressive disorder: A mental disorder involving depressive episodes that impair functioning and include persistent mood or interest changes. Seasonal affective disorder is a seasonal pattern specifier associated with depressive disorders, not a separate diagnostic family.
Seasonality: A recurring pattern of change associated with the seasons of the year. Seasonal affective disorder is one clinical expression of seasonal variation in mood and behavior.
Winter-pattern seasonal affective disorder: A seasonal depressive pattern in which episodes typically begin in autumn or winter and remit in spring or summer. This is the common presentation associated with reduced daylight and increased sleep or appetite.
Suprachiasmatic nucleus: A small hypothalamic brain region that coordinates circadian rhythms using signals from the eyes. It translates daily light exposure into timing signals relevant to seasonal mood changes.
Cognitive behavioral therapy for seasonal affective disorder: A structured psychotherapy adapted to address seasonal depressive symptoms and recurring winter patterns. It targets seasonal thoughts and behaviors and may help prevent recurrence.
Bipolar disorder: A mental disorder characterized by episodes of depression and mania or hypomania. Seasonal depressive episodes can occur in bipolar disorder, which also includes elevated mood episodes.
Light exposure: The amount, timing, and spectrum of light reaching an organism or its visual system. Researchers investigate which features of light exposure best predict symptoms and treatment response.
Summer-pattern seasonal affective disorder: A seasonal depressive pattern in which episodes typically begin in spring or summer and remit in autumn or winter. This less common presentation shows that seasonal depression is not limited to winter.

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