lose one's mind

Idioms and Phrases

Also, lose one's reason . Go crazy, lose one's sanity, as in I thought she'd lost her mind when she said she was going ice-fishing , or That assignment is enough to make me lose my reason . The first expression dates from the late 1500s; the second employs reason in the sense of “unimpaired mental faculties,” a usage dating from the late 1300s. Also see under go out of one's mind ; have all one's buttons .