The Oxford Thesaurus An A-Z Dictionary of Synonyms - mentaladj.

1) intellectual, cognitive, cerebral, perceptual, rational, conceptual, theoretical, noetic, abstract: The boy staggered us with his ability to perform rapid mental arithmetical calculations. 2) lunatic, mad, crazy, psychotic, demented, mentally ill, unstable, unbalanced, deranged, disturbed, daft, certifiable, Slang off one's rocker, nutty, batty, balmy or barmy, loony, screwy, bonkers, crackers, nuts, bananas, loco: My great-aunt has gone a bit mental in her old age.