The invention provides methods and compositions for the treatment of a subject having a psychiatric disease or disorder based upon the subject's genotype and/or the number of risk alleles carried by the subject, which risk alleles have been found by the present inventors to predispose a subject to antipsychotic medication induced weight gain (AIWG). The methods of the invention also provide for different treatments, or different treatment regimens, for the subject depending on the subject's risk of AIWG. Related compositions, in the form of kits, systems, and computer-readable media are also provided.
