balmy, bananas, batty, bughouse [slang], certifiable, crackbrained, cracked, crackpot, cranky [dialect], cuckoo, daffy, daft, dotty, fruity [slang], gaga, loco [slang], loony (also looney), loopy, meshuga (or meshugge), moonstruck, nuts, nutty, scatty [chiefly British], screwy, wacko (also whacko), wacky (also whacky)

aberrant, delirious, disordered

delusional, delusionary, disturbed, neurotic, obsessive-compulsive, paranoiac (also paranoic), paranoid (also paranoidal), psycho, psychotic, schizo, schizoid, schizophrenic, schizy (or schizzy)

eccentric, odd, oddball, off, pixilated (also pixillated), potty [chiefly British], queer, strange

foolish, senseless, witless

irrational, mixed-up, unreasonable

depressed, despondent

distracted, distraught, frantic, frenzied, haywire, hysterical (also hysteric), raving, wigged-out

amok (or amuck), ape, ballistic, berserk, nuclear

fixated, monomaniac, monomaniacal, obsessed