Major depressive disorder (MDD) is one of the most disabling mental illnesses and it has a significant impact on society. This review aims to provide updated scientific evidence about the epidemiology of MDD. A systematic literature review of the PubMed and MEDLINE databases was performed to identify articles on the prevalence of MDD and its correlates. The search was restricted to manuscripts published between January 2001 and December 2018. Sixty-three articles were included in the review. The lifetime prevalence of MDD ranged from 2 to 21%, with the highest rates found in some European countries and the lowest in some Asian countries. The main sociodemographic correlates were separated/divorced marital status and female gender. Child abuse, intimate partner violence, and comorbidity with other physical and mental disorders also were consistently associated with MDD across the reviewed studies. MDD is a highly prevalent condition worldwide. There are remarkable interregional differences in the disorder's prevalence, as well as in certain sociodemographic correlates. MDD is also highly comorbid with physical and mental health problems.

Objective Depression and obesity are two conditions with great impact over global health. This is mainly due to their high prevalence and the morbidity and mortality associated to both. The main aim of the present systematic review is to study the association between obesity and depression and the prognostic implications derived from it.Methods A literature review was performed in the PUBMED database. 18 articles were found (9 cross-sectional studies, 6 longitudinal studies and 3 clinical trials), which were reviewed by critical reading after which a summary of the main conclusions was written.Results These selected articles confirmed that there is indeed a link between depression and obesity, although there are doubts as to the significance of this relationship. Depression is a risk factor for obesity, especially atypical depression and in African-American adolescent males. Obesity is a risk factor for depression, especially in women and for recurrent depressive disorder. The comorbidity between obesity and depression is a risk factor for a bad prognosis illness.Conclusion The relationship between both disorders has been analysed in scientific literature, obtaining significant associations but also contradictory results. The most current data demonstrates that there is a relationship between both entities, although there is no unanimity when it comes to establishing the meaning of this association.

Objective: To investigate oxidative stress markers and antioxidants in bipolar disorder (BD).Methods: Electronic MEDLINE/PubMed/Cochrane‐Library/Scopus/TripDatabase search until 06/30/2019 for studies comparing antioxidant or oxidative stress markers between BD and healthy controls (HCs). Standardized mean differences (SMD) and 95% confidence intervals (CIs) were calculated for ≥3 studies.Results: Forty‐four studies (n = 3,767: BD = 1,979; HCs = 1,788) reported on oxidative stress markers malondialdehyde (MDA), thiobarbituric acid reactive substances (TBARS), and total nitrites; antioxidants glutathione (GSH), uric acid, and zinc; or antioxidantenhancing enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and GSH‐transferase (GST). Compared with HCs, BD was associated with higher GST (P = .01), CAT (P = .02), nitrites (P < .0001), TBARS (P < .0001), MDA (P = .01), uric acid (P < .0001), and lower GSH (P = .006), without differences in SOD, GPX, and zinc. Compared to HCs, levels were higher in BD‐mania for TBARS (P < .0001) and uric acid (P < .0001); in BD‐depression for TBARS (P = .02); and BD‐euthymia for uric acid (P = .03). Uric acid levels were higher in BD‐mania vs BD‐depression (P = .002), but not vs BD euthymia. TBARS did not differ between BD‐mania and BD‐depression. Medication‐free BD‐mania patients had higher SOD (P = .02) and lower GPX (P < .0001) than HCs. After treatment, BD did not differ from HCs regarding SOD and GPX.Conclusions: Beyond a single biomarker of oxidative stress, the combination of several parameters appears to be more informative for BD in general and taking into account illness polarity. BD is associated with an imbalance in oxidative stress with some phase‐specificity for uric acid and TBARS and possible treatment benefits for SOD and GPX. Future studies should take into account confounding factors that can modify oxidative stress status and simultaneously measure oxidative stress markers and antioxidants including different blood sources.