Poverty and common mental disorders in low and middle income countries: A systematic review⋆
Introduction
Common mental disorders (CMD), which include depression, anxiety and somatoform disorders, make a significant contribution to the burden of disease and disability in low and middle income countries (LMIC) (Lopez et al., 2006, WHO, 2001). In spite of high levels of poverty in LMIC, and the high burden posed by CMD in these countries, it is only in the last two decades that research has emerged that empirically addresses the relationship between poverty and CMD in these settings (Araya et al., 2003, Patel et al., 1999, Patel and Kleinman, 2003).
Recently, there has been debate in the literature regarding the strength of this relationship. Narrative reviews of 5 epidemiological studies from Brazil, Chile, India and Zimbabwe (Patel et al., 1999) and of a further 11 studies from a range of LMIC (Patel & Kleinman, 2003), suggest that CMD is strongly associated with lower levels of education and socio-economic status, as well as factors such as rapid social change, violence and insecurity, particularly among women. However, other reviews have concluded that when using measures of poverty such as consumption (defined as household per capita expenditure) or level of education, there is no consistent association with indicators of poor mental health (Das, Do, Friedman, McKenzie, & Scott, 2007).
The debate regarding the consistency and strength of the association between CMD and poverty is important, not only for conceptual reasons. A clear association between mental ill-health and poverty in LMIC would strengthen the case for the inclusion of mental health on the agenda of development agencies and on international targets such as the millenium development goals (MDGs) (Miranda and Patel, 2005, Sachs and Sachs, 2007). On the other hand, a weak association might suggest that interventions that target the purported social determinants of CMD would exert a limited effect (Das et al., 2007). In this instance, interventions might be better directed towards protecting individuals and households from adverse events (Das et al., 2007), as well as secondary and tertiary prevention.
This debate has taken place against the backdrop of a relatively well established field of study regarding poverty and mental health in high income countries (HIC) (Saraceno and Barbui, 1997, Saraceno et al., 2005). Unemployment (Weich & Lewis, 1998); adverse neighbourhood characteristics (Truong & Ma, 2006); low income, education, social class and socio-economic status (SES) (Lorant et al., 2003); and more recently income inequality (Pickett, James, & Wilkinson, 2006) have been shown to be associated with negative mental health outcomes in these countries. Theory regarding the mechanisms of this relationship is broadly divided into the “social causation” hypothesis, in which the conditions of poverty, such as stress, increased negative life events, worse physical health, reduced access to health care and stigma are thought to precipitate or maintain mental ill-health; and the “social selection” or “social drift” hypothesis, in which people living with mental illness are thought to drift into, or remain in, conditions of poverty, as a result of increased health expenditure, reduced income and lost employment (Dohrenwend et al., 1992, Saraceno et al., 2005). It has been hypothesised that the former theory may more readily apply to depression, whereas the latter may be more appropriate for schizophrenia (Saraceno et al., 2005).
In both HIC and LMIC, the definition of poverty appears to be central to examining its association with mental health. Traditionally, “absolute” poverty refers to a fixed income level and “relative” poverty refers to the level of income in relation to the mean or median income of a population (Toye & Infanti, 2004). A further distinction has been made between poverty and deprivation. Townsend argued that while deprivation refers to people’s unmet needs for a number of basic commodities, poverty refers to the lack of resources required to meet those needs (Townsend, 1979, Townsend, 1987). The subsequent development of the term “multiple deprivation” has come to refer to a range of indicators of social and economic deprivation and exclusion in poverty studies (Barnes et al., 2007, Toye and Infanti, 2004). Attempts have also been made to develop composite deprivation indices, such as the Index of Multiple Deprivation (IMD) (Department of the Environment, 2000) and the Human Development Index (HDI) (United Nations Development Programme, 2006).
In the light of the apparently contradictory findings from existing literature in LMIC, and the complex relationship between poverty and mental health, we carried out a systematic review of the literature to further elucidate the relationship between a variety of poverty indicators and CMD in LMIC. In particular, we aimed to describe the strength and nature of any association, and the type of poverty indicators most predictive of this relationship. These may inform national and international policy interventions.
Section snippets
Search strategies
This review was part of a broader systematic review examining the association between poverty and various mental illnesses. The search strategies therefore reflect that of the broader review, from which studies on CMD were subsequently selected. We searched the MEDLINE, EconLit and PsycINFO databases, using Medical Subject Heading (MeSH) terms (or equivalent terms for EconLit and PsycINFO) in February 2008 and again in January 2009 for published peer-review journal articles. Terms used to
Overview of studies
A total of 131 published articles representing 115 studies from 33 countries were included in the final analysis (Table 2). Among these, 18 studies were published in multiple articles and 3 articles reported on multiple studies within a single article. Details of all included studies are set out in Appendices.
Most of the studies were published in English, with 6 Portuguese, 5 Spanish and 1 Hebrew study. Most of the studies (77%) had as their primary purpose the reporting of the prevalence or
Summary of main results
This review presents findings on a complex body of epidemiological literature with heterogeneous methods, instrumentation, study settings and populations, published between 1990 and 2008. Despite the heterogeneity, the literature shows a relatively consistent trend in which CMD is associated with a range of poverty dimensions in LMIC. Among community-based studies that conducted multivariate analysis, 79% reported positive associations between a variety of poverty measures and CMD, and 6%
Conclusion
The epidemiological literature of the last 19 years indicates that the social and economic conditions of poverty are linked with CMD in LMIC. The mechanisms by which the cycle of poverty and CMD is maintained are complex and multi-dimensional. By presenting a systematic review of the literature, this paper has attempted to shift the debate from questions about whether poverty is associated with CMD in LMIC, to questions about which particular dimensions of poverty carry the strongest (or
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This paper was produced as part of the work of the Mental Health and Poverty Project, funded by the UK Department for International Development (DfID) for the benefit of LMIC. VP is supported by a Wellcome Trust Senior Research Fellowship in Tropical Medicine. JC is funded by the Western Cape Department of Health, South Africa. Initial drafting of this review was conducted as part of the Municipal Services Project, funded by the International Development Research Council. The views expressed are not necessarily those of the funders. We would like to thank Sara Cooper and Sarah Skeen for their assistance with the data extraction and Stephen Stansfeld for commenting on an earlier draft of this paper. We declare that we have no conflicts of interest.