Formulating a complete epidemiological profile of major depressive disorder: Investigating the global distribution, risk factors, outcomes, and burden of major depressive disorder

Abstract

BackgroundMajor depressive disorder (MDD) has been previously recognized as a severely impacting disorder.Although effective intervention strategies exist, access to treatment remains low, particularly in low-to middle-income countries. The purpose of this thesis was to formulate a complete epidemiological profile for MDD. This involved investigating (1) the global distribution of MDD;(2) the global burden of MDD in terms of disability-adjusted life years (DALYs), years lived with disability (YLDs) and years lost to premature mortality (YLLs) for the Global Burden of Disease Study 2010 (GBD 2010); (3) the contribution of MDD as a risk factor to the distribution and burden of suicide and ischemic heart disease; and (4) the risk factors of MDD and related avenues for further research. Such an epidemiological profile assists in identifying the size of the population who may need intervention for MDD. It provides policy-makers with information that can, along with considerations of cost-effectiveness and equity, be used in resource allocation within the health sector. For researchers, it identifies where the gaps in the literature exist regarding the epidemiology of MDD which need to be addressed with future research. MethodsA systematic literature review was conducted to capture studies of the prevalence, incidence, duration, and excess-mortality associated with MDD. Data points were integrated into a statistical disease model using DisMod-MR, a Bayesian meta-regression tool. DisMod-MR predicts epidemiological data for parameters and parts of the world with no raw data and also accommodates known methodological and ecological determinants of MDD.To estimate burden, disability weights measuring the severity of health loss from MDD were obtained from population survey data. These were combined with DisMod-MR prevalence data to calculate YLDs for MDD by age, sex, year, and country. To calculate YLLs, comparative risk assessment methodology was used to explore MDD as a risk factor for both suicide and ischemic heart disease. Data from additional systematic literature reviews and meta-analyses were used to obtain the pooled relative-risk of (1) ischemic heart disease in those exposed to MDD, and (2) suicide in those exposed to select mental and substance use disorders including MDD. For each risk factor-outcome pairing, population attributable fractions were calculated from the pooled relativerisks and DisMod-MR prevalence data. These were then used to calculate the proportion of DALYs originally allocated to ischemic heart disease and suicide in GBD 2010 which could be re-assigned iii to MDD. Finally, an investigation into the risk factors for MDD was presented, with a working example of how two previously established risk factors, child sexual abuse (CSA) and intimate partner violence (IPV), can impact on the distribution of MDD. ResultsThe literature search for epidemiological data identified 116 prevalence, 4 incidence, 5 duration, and 11 excess-mortality studies. DisMod-MR estimated over 298 million poi...

The molecular pathophysiology of mood disorders: From the analysis of single molecular layers to multi-omic integration

“…Among this group, Bipolar Disorder (BD) and Major Depressive Disorder (MDD) are the most prevailing syndromes in the general population. Indeed, BD affects around 1% of the global population (Ferrari, 2015), whereas MDD reaches a 12-months prevalence of 10.4% and a lifetime prevalence of up to 20.6% (Hasin et al, 2018). Mood disorders impose a substantial burden on patients and caregivers due to their recurrence and the frequently associated psychiatric comorbidities, including substance use, anxiety disorders, and suicidal behaviors (Isometsä, 2014).…”