poremetiti

1. (+ acc.) to disrupt; to upset; to disturb
   Kiša nam je poremetila sve planove za vikend. — The rain upset all our plans for the weekend.
   Štrajk je poremetio saobraćaj u gradu. — The strike disrupted traffic in the city.
2. (of balance, health) to upset; to throw off
   Put u Aziju mi je poremetio san. — The trip to Asia threw off my sleep.
3. colloq. (poremetiti se) to go crazy; to lose one's mind
   Da li si se poremetio? Pa to je skupo! — Have you lost your mind? That's expensive!

The imperfective is remetiti or poremećivati; the participle poremećen often means 'mentally disturbed'.