lose marbles

Related to lose marbles: part and parcel, Look before you leap, up to par, worse for wear

lose (one's) marbles

To be or become mentally deficient, incompetent, or deranged; to become of unsound mind. My poor grandmother started losing her marbles after she had a stroke. I've been so sleep deprived lately that it feels like I've lost my marbles!
See also: lose, marble
Farlex Dictionary of Idioms.

lose (all) one's marbles

 and lose one's mind
Fig. to go crazy; to go out of one's mind. What a silly thing to say! Have you lost your marbles? Look at Sally jumping up and down and screaming. Is she losing all her marbles? I can't seem to remember anything. I think I'm losing my mind.
See also: lose, marble
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • lose (one's) marbles
  • lose all one’s marbles
  • lose one’s marbles
  • lose one's marbles
  • lose your marbles
  • lose one's buttons
  • lose (one's) buttons
  • lose (one's) mind
  • lose your mind
  • lose one's mind