Inequality: An overlooked contributor to mental health disorders (part 1)

Most people are aware of common risk factors for mental illness, such as genetics, adverse life events, and substance abuse. But there are a number of less obvious and less talked about influences at play when it comes to the mental health of populations across the world — one of these is inequality.

Societal inequality is an often overlooked but significant factor in predicting whether or not someone will experience a mental illness in his or her lifetime. Mental health is influenced by a number of social, economic, and physical environments, and research demonstrates that the more unequal these environments, the more likely it is that a society will have a higher prevalence of mental health issues across its population — affecting both women and men, rich and poor.

Inequality Today 

Unequal distribution of income and wealth has been growing steadily — and to unprecedented levels — over the past three decades, and widening disparities have been recognized in countries at all levels of socio‐economic development. According to estimates by The World Inequality Database (WID), in 2016:

  • The global income share captured by the top 1% of earners rose to 20% — an increase of 4% from 1980.
  • The top 10% of earners in the U.S. captured 47% of the national income, or an average income 4.7 times greater than the average income in the economy as a whole. 
  • Between 20% to 30% of children whose parents fell within the bottom 10% of earners in the U.S. went to college, compared to 90% of children whose parents fell within the top 10%.
  • Other nations in which the top 10% acquired disproportionate amounts of income included Europe (37%), China (41%), Russia (46%), Canada (47%), and Brazil (55%).
  • The Middle East was the world’s most unequal region, with 60% of its national income captured by the top 10% of earners.
  • The wealthiest 1% of India’s population owned close to 60% of the country’s capital.

Researchers at WID predict that if inequality continues to rise at the rate it has since 1980, the world’s top 1% income share could increase from 20% today to more than 24% by 2050, while the global bottom 50% share could fall from its current 10% to less than 9%. 

Income Inequality and Mental Health

Research has shown that the overall health of a population tends to be better in societies with greater income equality, and rates of mental illness, violence, and drug abuse are often higher in those that are less equal. So what exactly are the mechanisms linking economic inequality to poor health? 

In a recent review published by the World Psychiatric Association, researchers assessed 26 studies that looked at rates of income inequality in societies across the world, mostly from high-income countries, and their respective prevalences of depression. From a geographical perspective, four were conducted at the country level, 14 at the regional level (i.e., state, county, district, and municipality), and eight at the neighborhood level — 15 of the studies were from the U.S. A few significant findings included: 

  • Over 61% of the studies showed a significant positive relationship between income inequality and risk of depression. Strong correlations between residing on the lower end of the earning spectrum and feelings of social defeat and inferiority, social isolation, alienation, and loneliness were observed. These feelings were exacerbated if poorer people lived in a society that enabled them to compare themselves to those of exceptional wealth, generating greater levels of stress — a common risk factor for depression. 
  • There was a significant positive relationship between the incidence rate of schizophrenia and income inequality at the country level — one proposed cause for this association being, again, that inequality negatively affects social cohesion and increases chronic stress, which may place individuals at an increased risk of mental health disorders like schizophrenia. 
  • Five of the studies stratified their analyses by gender, with three showcasing an association between income inequality and depression in females only. One of these three studies assessed a random sample of 8,060 women in the U.S. three years after giving birth, and found that 19% reported depressive symptoms, with 7.5% reporting fair or poor health. When compared to those in the highest fifth of the distribution of household income, women in the lowest fifth more often reported depressive symptoms (33% versus 9%) and fair or poor health (15% versus 2%).

Researchers also witnessed variations of the relationship between income inequality and mental health at different ecological levels, noting that: 

  • At the individual level, yet again, the effects of income inequality on general health were likely due to psychological stress. In a meta-analyses included in the review, researchers analyzed 208 laboratory studies surrounding psychological stressors and corresponding cortisol responses — an excess of which is associated with a number of physical and mental health issues. Results showed that cortisol responses were elicited if tasks appeared to threaten self-esteem or social status, demonstrating the heightened level of anxiety associated with even just the idea of having a low social rank.
  • At the neighborhood level, researchers observed two main contributors to mental health issues. The first was social comparison and status anxiety, which argues that making personal comparisons to someone better off may create feelings of social defeat or status anxiety, potentially leading to withdrawal and shame for those in lower social positions. The second was around the social capital hypothesis, arguing that income inequality erodes social capital. Social capital facilitates social trust and integration, and when it is undermined by income inequality, those affected are more likely to experience feelings of isolation and loneliness, putting them at an increased risk for mental health disorders, notably depression. 
  • At national and regional levels, researchers proposed the neo‐material hypothesis, which argues that higher levels of income inequality are tied to material deprivations necessary for good health. Examples of these include a lack of housing, education, healthy food, and accessible healthcare, all of which may contribute to poor physical health and an increased risk for mental health issues. 

These findings demonstrate that as the distribution of income spreads further and further apart, societies begin to break down — and if income inequality continues to rise across the world, it is highly likely that the associated negative impacts on mental health will worsen into the future.

Tune in next week as we’ll examine the impacts of gender disparities and social comparisons. In the meantime, be sure to sign up for our weekly #InsightNetwork for all the latest in biotech, psychedelic medicine, and more.