There are provided a therapeutic preparation for anxiety neurosis or depression which comprises a MC4 receptor antagonist as an effective ingredient; and a piperazine derivative represented by Formula [1]: [wherein Ar1 is a phenyl group, a substituted phenyl group, a naphthyl group or a substituted naphthyl group; Ar2 is a naphthyl group, a substituted naphthyl group, a quinolyl group, a group represented by the formula: (wherein R4 is a hydrogen atom or a halogen atom; and X—Y is CH—NH, CH—O, CH—S or N—O) or a group represented by the formula: (wherein R5 is a hydrogen atom, a hydroxyl group or a C1-10 alkoxy group); R1 is a hydrogen atom, a C1-10 alkyl group, a C3-8 cycloalkyl group, a C3-10 alkenyl group, a phenyl group, a 1-cyanoethyl group, a pyrimidin-2-yl group or an amidyl group; R2 and R3 are the same or different, and are each a hydrogen atom or a C1-10 alkyl group; A-B is N—CH2, CH—CH2, C(OH)—CH2 or C═CH; T1 is a single bond, —N(R6)— (wherein R6 is a hydrogen atom or a C1-10 alkyl group), —O—, —CH═CH— or —C(═O)—; n is an integer of from 1 to 10 and when T1 is a single bond, —CH═CH— or —C(═O)—, n is an integer of from 2 to 10 when T1 is —N(R6)— or —O—], or a pharmaceutically acceptable salt thereof.