lose (your) mind

to become crazy.

He was not the only prisoner to lose his mind.

Taking a child on a bike without a helmet – have you completely lost your mind?

• give someone chapter and verse
• give someone due
• give someone enough rope
• give someone enough rope to hang
• give someone enough rope to hang themselves
• give someone first refusal
• give someone food for thought
• give someone free reign
• give someone free rein
• give someone grief
• give someone hell
• give someone house room
• give someone pause
• give someone pause for thought
• give someone short shrift
• give someone some stick
• give someone ... stick
• give someone stick
• give someone the benefit of the doubt
• give someone the bird
• give someone the boot
• give someone the cold shoulder
• give someone the creeps
• give someone the elbow
• give someone the evil eye