"脑子有病" 的英语表达是 "mentally ill" 或 "mentally disorderd"。这个词组的来源是来自英语中的 "mental"（心理的，精神的）和 "ill"（病，不适）。
例句：
He has been diagnosed with a mental illness. 他被诊断患有精神疾病。
Mental disorders are becoming more and more common in our society. 精神障碍在我们的社会中变得越来越普遍。
It's important to seek help if you are struggpng with a mental health issue. 如果你正在经历心理健康问题，寻求帮助是很重要的。
She was suffering from a severe mental illness and required constant care. 她患有严重的精神疾病，需要持续的照顾。