While there are ongoing discussions concerning the effectiveness and side effects of antidepressants in the treatment of Major Depressive Disorder, some studies are being carried out on methods to decrease the duration and cost of treatment, and unsuccessful attempts of treatment.
Pharmacogenetics made it possible to implement a personalized treatment; it enables one to predict the reaction to the drug, in addition to its side effects. For instance, a genetic test may predict the suicidal ideation of a patient during the use of antidepressants, which may lead to the administration of a different treatment to this patient.
In the pharmacogenetic studies carried out on depression, the functions of two genes carrying serotonin were defined (5-HTTLPR, STin2). It was seen that a change in their sequence numbers (through deletion, addition, copying, etc.) would change the genetic functions during the use of antidepressants. Nevertheless, pharmacogenetic examinations are limited by the fact that depression is a complex disorder arising from the interaction of genetic and environmental factors.
Genetic examinations reported that the significance of participation in major depression, and that the risk of incidence increases 2-3 times by 37% if it is present in the family. Epigenetic researches are being used to control the non-genetic factors. Epigenetics interprets genetic modifications through the examination of both hereditary factors and environmental factors (age, nutrition, smoking, etc.).
In the MDD treatment, it was observed that different reactions were given to the same drug in time. Epigenetics interprets this as follows: Environmental factors and antidepressants cause modifications in genes, and the modified genetic structure prevents the same antidepressant from showing the same effect later on. Accordingly, on another use, the patient may not feel the same effect in the antidepressant which s/he previously obtained a positive result from. This situation shows the significance of using the pharmacogenetic data (e.g. Saliva test) as a guide in the antidepressant treatment.