疾病发生的原因简称病因，又可称为致病因素。它是指作用于机体的众多因素中，能引起疾病并赋予该病特征的因素。
某些心理疾症明显是导因于大脑组织的病变，例如阿兹·海默症，但是绝大部分这类疾病的致病机转，医界仍然不知道知或未能证明。
Some mental disorders, such as Alzheimer disease, are clearly caused by organic disease of the brain, but the causes of most others are either unknown or not yet verified.
感恩表征：林博士因痔疾接受疹治时以临时起意的笑话奉与医师，表感恩。
Tokens of Gratitude: Jokes spoken by Dr. Yutang Lin to his physician while being treated for Hemorrhoids.
近年来发生人类因食用各种肉类而患上重疾的事件，频频亮起的警号灯并没让人类醒悟。
Recent incidents where people became infected with diseases after eating the meat of various animals have caused great alarm, yet still failed to wake us up.
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