Inequality and mental illness: Comment in Lancet Psychiatry by Professors Wilkinson and Pickett
For at least 40 years, research evidence has been accumulating that societies with bigger income differences between rich and poor tend to have worse health and higher homicide rates. More recently, this has been contextualised by observations that more unequal societies not only suffer higher rates of poor health and violence, but also of other outcomes which tend to be worse lower down the social ladder – including teenage births, lower maths and literacy scores, obesity and imprisonment. (1)
Taken together, the hundreds of research papers on these effects of inequality suggest that the relationships meet the epidemiological criteria for causality. (2) Though there may be some ‘reverse’ causality through which poor health – for example – increases inequality (2), much more important are the ways in which inequality damages health and social functioning. The causal pathways seem to be mediated by the effects of inequality on social capital and trust and are largely independent of absolute material living standards and of the benefits of public services. (3-4)
Mental illness is the most recent addition to this list of effects of greater inequality. In a meta-analysis of research on the relation between income inequality and mental illness in The Lancet Psychiatry, Wagner Ribeiro and colleagues find that greater inequality is associated with higher rates of mental illness – particularly of depression and anxiety disorders. (5)
This is particularly interesting in the light of an earlier review by Johnson and colleagues that, on the basis of a very large body of evidence, showed that the human brain’s dominance behavioural system, which processes issues to do with social dominance and subordination, is likely to be involved in a broad range of mental illnesses and personality disorders. (6) Specifically, they suggested that externalizing disorders, mania proneness, and narcissistic traits are related to heightened dominance motivation, while anxiety and depression are related to subordination (or the attempt to avoid it) and to submissiveness.
More frequent occurrence of mental conditions that involve the dominance behavioural system in societies with bigger income differences between rich and poor would be consistent with the suggestion that greater inequalities increase the salience of issues to do with dominance and subordination. The evidence that many health and social problems with inverse social gradients are also more common in more unequal societies (7) carries the same implication.
Ribeiro and colleagues’ meta-analytic review of the relation between mental illness and income inequality (5) finds modest effect sizes―0.06 for any mental health problem and 0.12 for depressive disorders―but two points need to be kept in mind. First, exposure to inequality affects the whole population, so even a small effect size means that the additional number of people with mental illness attributable to inequality is very large. Second, these effect sizes come from multilevel models which exclude the direct effects of individual high or low income. However, insofar as some of the effect of individual income is to create the feelings of superiority and inferiority in relation to others through which inequality is likely to have its impact, this leads to a substantial under-estimate of the effects of inequality.
The quality of social relations is a powerful influence on mental health. There is a growing body of research which suggests that greater inequality is a social stressor regardless of average living standards. (8) A study in 31 European countries found that status anxiety was higher at all income levels in more unequal societies, again suggesting that increased inequality heightens the importance of status differences. (9)
An illustration of the powerful psychosocial effects of relative poverty comes from a study which interviewed people experiencing poverty in seven countries at different levels of development. (10) It found that although material circumstances of the poor in countries as rich as Norway or Britain appear luxurious by comparison with poverty in India or Pakistan, the experience of poverty was remarkably similar. Being poor in relation to others meant people in each society were unable to escape feeling despised, shamed, and humiliated. Whether people live in a shack with an earth floor and no sanitation, or in a three bedroom house with fridge, washing machine and television, low social status is experienced as overwhelmingly degrading. As inequality makes social status more important, this also explains why violence, triggered by loss of face, humiliation and disrespect, is more common in more unequal societies. (11)
As the American anthropologist, Marshal Sahlins, pointed out, poverty is above all, “a relation between people...an invidious distinction between classes…” p.37. (12) It is also a warning against the common assumption, made also by Ribeiro and colleagues, that associations with poverty, even in developed countries, necessarily reflect the effects of material rather than psychosocial processes. We all need to feel valued.
Richard Wilkinson* and Kate Pickett**
* Emeritus Professor of Social Epidemiology, University of Nottingham
** Professor of Epidemiology, University of York.
Professor Richard Wilkinson, Department of Health Sciences, Seebohm Rowntree Building, Area 2, University of York, Heslington, York, YO10 5DD, UK. Email: firstname.lastname@example.org
Conflict of Interest Statement
Both authors are trustees of The Equality Trust, a registered charity
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