Philadelphia, PA, December 6, 2007 – As in most fields of medicine, psychiatry researchers are working to identify specific types of patients, through their individual genetic variations, that may better benefit from particular drugs or combinations of drugs than other patients. A new study, published in Biological Psychiatry’s December 1st issue, investigated whether depressed patients with a particular genetic variation would better respond to the addition of lithium to their treatment regimen, as opposed to an antidepressant-only treatment.