An evolutionary based social rank explanation of why low income predicts mental distress: A 17 year cohort study of 30,000 people

Does income relate to health due to psychosocial or material factors? Consistent support for the psychosocial hypothesis requires operationalization with income rank not the Yitzhaki Index

“…Income rank negatively relates to both self-report and objective measures of health. Our findings are consistent with a growing body of literature comparing the material and psychosocial processes on health (for example Martikainen, Adda, Ferrie, Smith, & Marmot, 2003;Elgar et al, 2013;Daly, Boyce, & Wood, 2015;Boyce, Brown, & Moore, 2010;Wood, Boyce, et al, 2012), and contrast the studies by Eibner & Evans (2005) and Li & Zhu (2006) who report mixed findings for an effect of rank on health. A failure to find a significant effect of rank in the two outlier studies may be the result of using datasets in which information on individual income was only collected being within in a broad income band (as in the case of the study by Eibner & Evans, 2005), rather than the actual income level, which is less suitable for forming the rank variable, or the use of a deflated income per capita household income variable (as in the case of the study by Li & Zhu, 2006), which assumes that people compare relative spending power rather than simply how much they are earning relative to others.…”

“…This parallels findings with mental health and depressive symptoms as the outcome (Elgar et al, 2013;Hounkpatin et al, 2015;Wetherall, Daly, Robb, Wood, & O'Connor, 2015;Wood, Boyce, et al, 2012) as well findings from a study by Subramanyam et al (2009) which indicated that percentile income rank significantly predicted self-rated health in a US population after controlling for actual income. The income rank specification is consistent with the psychosocial hypothesis but differs from the Yitzhaki Index in that it proposes that health is not necessarily related to the magnitude of the difference, but rather the position of income on the income distribution within a comparison group.…”

“…This function represents the average difference between an individual's income and the income of all individuals with higher income within the same reference group. Studies using the Yitzhaki Index to assess the psychosocial hypothesis have yielded mixed results, with many studies finding the Yitzhaki Index relates to health (for example, Eibner & Evans, 2005;Eibner, Sturn, & Gresenz, 2004;Kondo et al, 2008;Subramanyam, Kawachi, Berkman & Subramanian, 2009;Yngwe, Kondo, Hagg, & Kawachi, 2012;Yngwe, Fritzell, Burstrom & Lundberg, 2005;Yngwe, Fritzell, Lundberg, Diderichsen, & Burstrom, 2003), while many others (for example Gravelle & Sutton, 2009;Jones & Wildman, 2008;Li & Zhu, 2006;Lorgelly & Lindley, 2008;Wildman, 2003) Meanwhile, a new line of evidence (Boyce, Brown, & Moore, 2010;Daly, Boyce, & Wood, 2015;Hounkpatin, Wood, Brown, & Dunn, 2015;Wood, Boyce, Moore, & Brown, 2012) has consistently suggested that it is the rank (ordinal position) of an individual's income that is psychosocially important for their health. For example, Daly, Boyce & Wood (2015) compared the effects of income and income rank on self-rated health, obesity, and allostatic load, and they found that income rank was significantly associated with each health measure in two British populations, even after controlling for the effects of actual income.…”

Recalibrating the spirit level: An analysis of the interaction of income inequality and poverty and its effect on health

“…Beckfield (2004) analyzed the relationship across countries and over time, finding limited empirical evidence for the adverse role of income inequality. Analyses based on panel data are also mixed: some support the income inequality hypothesis with regard to mental distress (Wood, Boyce, Moore, & Brown, 2012) and happiness (Layard, Mayraz, & Nickell, 2010); others find no effect of inequality on mortality (Gerdtham & Johannesson, 2004), or self-reported health (Lorgelly & Lindley, 2008). These results overall suggest caution in assessing the robustness of the effect of income inequality on mortality/morbidity.…”

Integrating Positive and Clinical Psychology: Viewing Human Functioning as Continua from Positive to Negative Can Benefit Clinical Assessment, Interventions and Understandings of Resilience

“…An example of this is the withdrawal, hypervigilance, depressed affect, etc. that results from perceiving that one is of low social rank (Griffiths, Wood, Maltby, Taylor, & Tai, 2014;Taylor et al, 2010;Taylor, Gooding, Wood, Johnson, & Tarrier, 2011); necessary, perhaps, when the pack may set against one if different actions were taken, but wholly perverse when triggered by being of low income in today's society (Daly, Boyce & Wood, in press;Wood, Boyce, Moore, & Brown, 2012). However, whilst we may have some evolutionary propensity to react more to being low on some constructs than others, the extent to which this reaction occurs and is seen as intolerable (by the individual concerned, or by those providing or resourcing the treatment) depends in part on what society itself sees as intolerable and indeed treatable.…”