It is intended to provide a novel method of treating integration dysfunction syndrome. Namely, 5 mg to 120 mg/day of an active compound (1R,2S,3R,4S)-N-[(1R,2R)-2-[4-(1,2-benzoisothiazol-3-yl)-1-piperazinylmethyl]-1-cyclohexylmethyl]-2,3-bicyclo[2.2.1]heptane dicarboxyimide or its pharmaceutically acceptable salt (for example, hydrochloride) is orally administered to a patient with integration dysfunction syndrome once a day. According to this method, broad symptoms of integration dysfunction syndrome, in particular, positive symptoms and negative symptoms, can be ameliorated without causing any extrapyramidal reactions.
