noun
seasonal affective disorder; SAD
A psychiatric term for a type of depression that occurs at a specific season, usually winter.
季節性情動障害は、冬に日照時間が短くなることで発症しやすい。
Seasonal affective disorder tends to occur in winter when daylight hours become shorter.
冬季うつ病 is a more colloquial term for winter depression, while 季節性情動障害 is the formal psychiatric diagnosis.
A compound of 季節性 (seasonal) + 情動 (emotion) + 障害 (disorder), calqued from English 'seasonal affective disorder'.