they aren't playing with a full deck

When adults have mental issues, whether diagnosed, or gone undiagnosed, that lead them to act out erratically, or not like a logical, pragmatic individual.

Example: "they aren't playing with a full deck."

Damien: I ain’t going after nobody! They are fully grown adults. If they choose to go out that door, mad, or whatever, so be it.

Jimmie: Well, they may be fully grown adults, but…

Felicity: (Cutting her father, Jimmie, off). But they aren’t playing with a full deck.