Depressive hypochondria can evolve into a serious delusional type in which the person is convinced of the disorder and has no insight into the irrationality of her fears. She is at risk for suicide.

严重的抑郁病症可以演变成妄想型，病人相信身染重病，对自己担心的非理性没有正确认识，甚至有自杀的倾向。

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Another risk factor is a condition called delusional disorder -- and in particular the "persecutory type" -- that causes people to believe that someone is plotting against them, Rossiter said.

CNN: Insights on why people 'snap' and kill