Assays and methods for selecting a treatment regimen for a subject with depression

A method for treating a human subject with depression, comprising administering a composition comprising an effective amount of a folate-containing compound to a human subject, who is diagnosed to have depression, and is further determined to carry a combination of the following single nucleotide polymorphisms (SNPs):

• (i) a SNP at position 677 of SEQ ID NO. 1 or position 27 of SEQ ID NO. 7 (identified by rs1801133) comprising at least one thymine “T” allele, wherein the SEQ ID NO. 1 and SEQ ID NO. 7 are each independently a portion of a genomic nucleic acid sequence of methylenetetrahydrofolate reductase (MTHFR);
• and
• (ii) a SNP at position 2756 of SEQ ID NO. 2 or position 27 of SEQ ID NO. 9 comprising at least one guanine “G” allele, wherein the SEQ ID NO. 2 and SEQ ID NO. 9 are each independently a portion of a genomic nucleic acid sequence of methionine synthase (MTR)
• based on the recognition that the combination of said SNP alleles is associated with positive, symptom-reducing response to the folate-comprising compound.