WordNet (r) 3.0 (2006):

folie
    n 1: (psychiatry) a psychological disorder of thought or
         emotion; a more neutral term than mental illness [syn:
         mental disorder, mental disturbance, disturbance,
         psychological disorder, folie]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "folie":
   aberration, abnormality, alienation, brain damage, brainsickness,
   clouded mind, craziness, daftness, dementedness, dementia,
   derangement, disorientation, distraction, furor, insaneness,
   insanity, irrationality, loss of mind, loss of reason, lunacy,
   madness, mania, mental deficiency, mental derangement,
   mental disease, mental disorder, mental disturbance,
   mental illness, mental instability, mental sickness,
   mind overthrown, mindsickness, oddness, pixilation, possession,
   queerness, rabidness, reasonlessness, senselessness,
   shattered mind, sick mind, sickness, strangeness, unbalance,
   unbalanced mind, unsaneness, unsound mind, unsoundness,
   unsoundness of mind, witlessness