This is an observational (non-interventional) prospective study, carried out in drug-naïve outpatients who start a treatment with escitalopram, fluoxetine, sertraline or quetiapine. Five blood samples are collected (i.e. before initiating the drug, and then after 1, 2, 4 and 8 weeks of treatment). It does not affect the choice or the treatment dose. The primary objective of this study is to measure the association between the EDIT-B® editing signature and response to pharmacological treatment in drug-naïve patients. Results of this research could provide an aid to early diagnosis, optimize pharmacological treatment and guide clinical practice towards individualized treatment.

Inclusion Criteria:

• Adult drug-naïve outpatients suffering from depression and/or bipolar disorders who start a pharmacological treatment with escitalopram, fluoxetine, sertraline or quetiapine and who gave his written informed consent to participate in the present study.

Exclusion Criteria:

• Any patient without capacity of discernment or with harmful use of psychoactive substances

The study population includes drug-naïve adult outpatients (aged 18 or over) with depression (F32-33) and/or bipolar disorder (F30-F31) who start escitalopram, fluoxetine, sertraline or quetiapine.