Abstract: A method for predicting a negative symptom change in a subject during drug therapy is provided. The method comprises isolating genomic DNA from a sample of the subject, and genotyping a T5988C marker of GRIN2B gene. A GRIN2B 5988 T/T genotype is predictive of a negative symptom improvement in the subject in response to drug therapy. The drug therapy may be clozapine therapy. Also provided is a method of identifying a polymorphism in a nucleotide sequence of interest that is predictive of response to drug therapy comprising the steps of assessing negative symptom improvement in a plurality of subjects during the course of drug therapy, isolating a sample comprising DNA from each subject, genotyping one or more nucleotide sequences of interest in the DNA of each subject to identify one or more polymorphisms that exist in the one or more nucleotide sequences of interest, wherein correlation of a significant improvement of negative symptoms with one or more polymorphisms is predictive of response to drug therapy.

Abstract: A method for predicting a negative symptom change in a subject during drug therapy is provided. The method comprises isolating genomic DNA from a sample of the subject, and genotyping a T5988C marker of GRIN2B gene. A GRIN2B 5988 T/T genotype is predictive of a negative symptom improvement in the subject in response to drug therapy. The drug therapy may be clozapine therapy. Also provided is a method of identifying a polymorphism in a nucleotide sequence of interest that is predictive of response to drug therapy comprising the steps of assessing negative symptom improvement in a plurality of subjects during the course of drug therapy, isolating a sample comprising DNA from each subject, genotyping one or more nucleotide sequences of interest in the DNA of each subject to identify one or more polymorphisms that exist in the one or more nucleotide sequences of interest, wherein correlation of a significant improvement of negative symptoms with one or more polymorphisms is predictive of response to drug therapy.

Abstract: An association of a genetic marker with psychosis, a mood disorder, or a combination thereof is provided. Polymorphisms in the GRIN2B gene or alteration in the levels of GRIN2B gene products can be used to diagnose or identify a susceptibility to psychosis, a mood disorder, or a combination thereof. In certain examples, polymorphisms in the 3?UTR of the GRIN2B can be associated with psychosis, a mood disorder, or psychosis and a mood disorder. Also provided are kits for determining the presence or absence of such polymorphisms.