The present invention relates to a method of decreasing cholesterol or low density lipid protein in a subject in need thereof comprising: administering to said subject a pharmaceuticaly effective amount of a composition comprising dextromethorphan.The present invention also relates to a method of treating a subject suffered from bipolar II disorder, comprising administering to said subject a therapeutically effective amount of valproic acid and a combination of dextromethorphan and memantine, wherein the dose of dextromethorphan or memantine is a low dose not sufficient to work as a N-methyl-D-aspartate (NMDA) receptor antagonist.The present invention further relates to a composition for treating bipolar II disorder, which comprises valproic acid and a combination of dextromethorphan and memantine, wherein the dose of dextromethorphan or memantine is a low dose not sufficient to work as a N-methyl-D-aspartate (NMDA) receptor antagonist.
