<P>PROBLEM TO BE SOLVED: To provide an animal model for studying depression, schizophrenia or Alzheimer's disease. <P>SOLUTION: There is provided a mammal whose genome is disrupted by recombination at Glycine N-methyltransferase (GNMT) gene locus. The method of generating an animal model comprises disruption of GNMT gene in the animal by recombination at GNMT gene locus. The screening method of drug candidate using the animal model, comprises: (a) administering a drug candidate to the animal model, (b) measuring the response of the animal to the drug candidate, (c) comparing the response of the animal with that of an animal having a wild type GNMT gene, and (d) screening the drug candidate based on the difference in response observed between the animal obtained from the observation and the animal having a wild type GNMT gene. <P>COPYRIGHT: (C)2011,JPO&INPIT 
ANIMAL MODEL, PRODUCTION METHOD THEREOF AND DRUG CANDIDATE SCREENING METHOD USING THE SAME