求翻译 Falling leaves, withering flowers, cold winds, faint sunshine. For many people late autumn can be a season of gloom and depression. Spirits can decline into melancholy. It can be a time of feeling low and sad with common signs of anxiety, irritability, loss of interest in life, withdrawal from social events and inability to concentrate. "The exact cause of this condition, often called seasonal depression or seasonal affective disorder (SAD), is not known yet," says Chen Jue, associate professor at Shanghai Mental Health Center. "But recent studies indicate that weather change is influential and strongly suggest that this condition is caused by changes in the availability of sunlight."