Research suggests that the reason for this could be the ageing effects of stress, and the persistent relaxation of facial muscles which can be an effect of long term anti-depressant use.

• 研究表明这种现象的原因可能是紧张导致的衰老效应，而脸部肌肉的持续松弛可能是长期服用抗抑郁药物的结果。