Provided herein are methods of diagnosing depressive disorders in a subject by comparing a CDP-diacylglycerol synthase 1 enzyme activity or expression level to enzyme activity or expression level of CDP-diacylglycerol synthase 1 in a control subject. Also herein are methods of predicting therapeutic efficacy of an antidepressant drug in a subject with depressive disorders by monitoring enzyme activity or expression level of CDP-diacylglycerol synthase 1 in the subject. Further provided herein are methods of identifying a compound effective to treat or alleviate the symptoms of depression by monitoring enzyme activity or expression level of CDP-diacylglycerol synthase 1 in a tissue. Further provided are kits for diagnosing depressive disorders.
