The utilization of biomarkers, which include objectively measureable and assessable indicators of a biological process or biological state, in treatments is disclosed. Particularly, biomarkers enabling optimisation of treatment regimes and the use of the biomarkers in tests for the prediction of optimised treatments and treatment outcomes in the treatment of Major Depressive Disorder (MDD) are disclosed. Measurable and assessable cognitive and/or genomic parameters can be biomarkers indicating changes in system severity of MDD.
