not (quite) right in the head

not (quite) right in the head

Mentally unwell or unstable. The term can be used both literally and hyperbolically. Tim has been behaving very erratically lately—I'm afraid that accident has left him not quite right in the head. Liz isn't right in the head if she thinks that plan will work!
See also: head, not, right
Farlex Dictionary of Idioms.

not right in the head

Mentally unsound, as in Physically, she's quite healthy for ninety, but we suspect she's not right in the head . This usage was first recorded as right in his wits in 1662.
See also: head, not, right
The American Heritage® Dictionary of Idioms by Christine Ammer.

not right in the head

SPOKEN, OFFENSIVE
If someone is not right in the head, they are mentally ill. According to Great-aunt Louise, the grandmother wasn't quite right in the head.
See also: head, not, right
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • be not right in the head
  • go crazy
  • everyone and their mother
  • chain (someone or something) to (something)
  • chain to
  • everyone and their dog
  • everyone and their brother
  • everyone and his mother
  • everybody and his mother
  • everybody and their mother