While there is increasing evidence of an association between poor mental health and the experience of poverty and deprivation, the relationship is complex. We discuss the epidemiological data on mental illness among the different socio-economic groups, look at the cause--effect debate on poverty and mental illness and the nature of mental distress and disorders related to poverty. Issues related to individual versus area-based poverty, relative poverty and the impact of poverty on woman's and child mental health are presented. This review also addresses factors associated with poverty and the difficulties in the measurement of mental health and illness and levels/impact of poverty.

Key words Mental health--poverty--socio-economic status

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The relationship between poor mental health and the experience of poverty and deprivation has been well studied and an association between the two factors has been established. The World Health Organization report (1) on mental health states 'Mental disorders occur in persons of all genders, ages, and backgrounds. No group is immune to mental disorders, but the risk is higher among the poor, homeless, the unemployed, persons with low education......'. The link is however, complex and is influenced by numerous factors.

Prevalence of mental illness and socio-economic status

Psychiatric epidemiological surveys since the late 1930s have reported higher rates of mental illness in low-income communities (2). Early studies showed this in major mental illnesses like schizophrenia. Recent evidence suggests this is the case with other groups of psychiatric disorders as well (3).

Schizophrenia: Early work of Faris and Dunham in 19392 showed first admissions for schizophrenia to concentrate in the inner city, lower socio-economic areas of Chicago. This was supported by other studies that followed (4). Some later studies however reported that the actual incidence of schizophrenia does not vary with social class, but rather that the lower socio-economic status was secondary to the psychotic illness (5).

Mood disorders: Analyses of the data from the Epidemiological Catchment Area study, a large community survey in the United States (6), indicated that the lowest socio-economic group manifested twice the risk of major depressive disorder (MDD) than the highest income group. The National Comorbidity Survey (NCS) concluded that individuals with low socio-economic status demonstrate higher risk for MDD than individuals who are economically well-off (7). Bipolar affective disorder on the other hand is reported to occur more in the upper socio-economic strata (8).

Common mental disorders: Minor or nonpsychotic psychiatric morbidity that is largely constituted by symptoms of anxiety and depression are frequently encountered in the general population. These are among the most important causes of morbidity in primary care settings and produce considerable disability (9,10). While earlier studies looking at socio-economic issues focused on schizophrenia, recent literature has concentrated on the association with this group of disorders. These, termed "common mental disorders" (CMDs), are reported to be most prevalent among those with the lowest material standard of living, especially among those with a long-term experience of poverty (3,4) .The explanatory models of persons suffering from common mental disorders have been described in a number...