seasonal affective disorder
noun [ U ] uk/ˌsiː.zən.əl əˈfek.tɪv dɪˌsɔː.dər/ us/ˌsiː.zən.əl əˈfek.tɪv dɪˌsɔːr.dɚ/ (abbreviation SAD)
季节性情感障碍（指人在冬季时因日照缩短而表现出的抑郁）
a medical condition in which a person does not have much energy and enthusiasm during the winter because of the reduced period of natural light