Inflammation and depression: a study protocol to dissect pathogenetic mechanisms in the onset, comorbidity and treatment response.

About one third of patients suffering from Major Depressive Disorder (MDD) do not respond to any antidepressant medications and 75% experience relapses and general health deterioration. Importantly, inflammation can contribute to such negative outcomes, as well as to cause depression in patients who have been exposed to adverse childhood experiences and/or to viral infections, including COVID-19. Depressed patients also have an increased risk for developing comorbidities, such as cardio-metabolic dysfunctions, where inflammatory alterations, again, play a role in connecting MDD and these comorbid conditions. Here, we present our study protocol funded by the Italian Ministry of Health in the context of the PNRR call (M6/C2_CALL 2022; Project code: PNRR-MAD-2022-12375859). The project aims to clarify the role of inflammation: i) in the onset of depression in association with environmental factors; ii) in the mechanisms associated with treatment response/resistance; iii) in depression and its comorbidity. To reach all these aims, we will perform biochemical, transcriptomic, genetic variants analyses on inflammatory/immune genes, pharmacokinetics and machine learning techniques, taking advantage of different human cohorts (adolescent depressed patients exposed to childhood trauma; adult depressed patients; treatment resistant depression patients; both prevalent and incident depression cases identified within a large population cohort). Moreover, we will use