Immune-inflammatory and autoimmune mechanisms in postpartum depression

Postpartum depression is a debilitating mental disorder with a high prevalence, usually related with a past psychiatric history of major depressive disorder, postpartum depression, bipolar disorder, premenstrual syndrome (PMS), and perinatal depressive symptoms during gestation. However, the existing literature does not sufficiently elucidate the pathophysiology of this clinical entity which appears in such a crucial period of woman's life. This review aims to search the available data regarding the involvement of immunological and autoimmune mechanisms in its onset. A literature review was conducted using web-based search engines provided by PubMed (for Medline database) and Google Scholar. Manuscripts in English and Greek language were included for the period 19902017. Nowadays, a large body of evidence indicates that depressive disorders are accompanied by activated neuro-immune, neuro-oxidative and neuro-nitrosative stress (IO&NS) pathways. However, clinical research regarding the biological mechanisms associated with PPD is a tough challenge as pregnancy and puerperium are periods of adaptive changes in pregnant women by definition. Two of the systems that have been studied as potentially contributing to the onset of PPD are: the activation of the Inflammatory Response System (IRS) and the deregulation of the Hypothalamic-PituitaryAdrenal axis (HPA). Controversial data indicate dysregulation of cytokines and other inflammatory agents in patients with PPD, as well as, a close correlation of immune-inflammatory mechanisms and kynurenine pathway. PPD has been closely associated with autoimmune diseases. It is notable that this entity shares many common traits with autoimmune diseases such as the genetic susceptibility, family history, the high correlation with other autoimmune diseases, clinical exacerbations and remissions, women's superiority in prevalence, and the possible re-occurrence during a future pregnancy. These facts suggest that the typical postpartum flare pattern, and other clinical characteristics, point towards an autoimmune etiology for PPD. There are indications that immune-inflammatory and autoimmune mechanisms may be the key to deciphering the complex pathophysiological pathways associated with the onset of PPD. Clinical studies have been insufficient to make clear the causative correlations of the underlying mechanisms involved. Future research could focus on the immune-inflammatory processes associated with the onset of the disease, as well as on potential biomarkers for an early diagnosis and an effective treatment of PPD.