sea·son·al affective disorder .sēz-ən-əl- n depression that tends to recur as the days grow shorter during the fall and winter abbr. SAD
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(SAD) a cyclically recurring mood disorder characterized by depression, extreme lethargy, increased need for sleep, hyperphagia, and carbohydrate craving; it intensifies in one or more specific seasons, most commonly the winter months, and is hypothesized to be related to melatonin levels. In DSM-IV terminology called mood disorder with seasonal pattern.Medical dictionary. 2011.