The present invention provides methods for treating depression such as major depressive disorder (MDD) in an individual. The invention further provides methods for determining if an individual suffering from depression is likely to respond favorably or experience an enhanced treatment effect in response to treatment with vortioxetine. The present invention also provides methods for treating cognitive impairment in an individual, optionally wherein the individual also suffers from depression and/or MDD. The invention further provides methods for determining if an individual suffering from cognitive impairment is likely to respond favorably or experience an enhanced treatment effect in response to treatment with vortioxetine. The methods comprise determining the presence of polymorphisms in the collagen, type XXVI, alpha 1
