"脑子有病"用英语可以表达为"to have a sick mind"或者"to have a diseased mind"。

这个短语的来源可能来自于人们将脑子看做是一个像其他器官一样容易生病的器官。

例句：

He has a sick mind and always thinks about dark things.（他脑子有病，总是想到黑暗的东西。）

She has a diseased mind and always says hurtful things.（她脑子有病，总是说伤人的话。）