[What to consider when choosing an antidepressant to treat unipolar depression]

Major depression is a wide and heterogeneous concept. It is defined by DSM by the presence of 5 out of 9 different criteria. Most studies use the DSM definition of depression to screen patients who are then selected by applying strict inclusion and exclusion criteria. This process helps to unify the characteristics of the population under study and to focus more specifically on the variables that will determine safety and efficacy of the drug being studied. However, this ideal population under study is far from the real people that will be prescribed the drug once it is marketed. It is believed, theoretically at least, that most antidepressants of the same class have the same effect. However, advances in pharmacogenetics, pharmacodynamics and pharmacovigilance have shown new side effects and unexpected interactions that demand we take other precautions when prescribing an antidepressant to any given patient. Therefore, it is necessary to know the individual characteristics of each patient.