2 sentences

1. 你这个神经病，快别乱说话了！

   nǐ zhè​ge shén​jīng​bìng, kuài bié luàn shuō​huà le!

   You lunatic, stop talking nonsense!

   Source: Dong Chinese Dictionary

2. 医生认为他这种怪异的行为是由于神经病引起的。

   yī​shēng rèn​wéi tā zhè zhǒng guài​yì de xíng​wéi shì yóu​yú shén​jīng​bìng yǐn​qǐ de.

   The doctor believes his strange behavior is caused by a mental illness.

   Source: Dong Chinese Dictionary