Several candidate gene association studies have been carried out in recent years and have identified some promising markers of antidepressant outcome. Numerous studies have implicated SLC6A4 variation in antidepressant treatment outcome, although the outcome phenotypes have varied substantially and a recent meta-analysis found no overall effect [Taylor et al 2010]. Other promising leads include: FKBP5, which encodes a protein involved in glucocorticoid trafficking [Binder et al 2004]; HTR2A, encoding the serotonin 2A receptor [McMahon et al 2006]; and ABCB1, which encodes a p-glycoprotein that affects brain concentrations of some antidepressants [Uhr et al 2008]. All of these findings await robust replication in large samples.
