It may be that higher levels of inequality have increased the incidence of poor mental wellbeing in the community. A recent book suggests a causal mechanism from one to the other.

International research shows that there is a socioeconomic status (or class) gradient, in which those with low SES experience higher morbidity from respiratory and cardiovascular diseases, ulcers, rheumatoid disorders, a number of cancers, psychiatric diseases, dementia and so on. Often those at the bottom of the SES scale have life expectancies five to ten years shorter than those at the top of the scale.

Part, but not all, of the differences can be explained by differences in access to health care and by ‘unhealthy life styles’ such as the consumption of tobacco and excess alcohol, lack of exercise and obesity. Even so, there remains a significant residual which cannot be so readily explained.

The intermediating channel seems to be stress. There is a substantial biomedical literature which has established that individuals are more at risk from the stress-sensitive diseases just mentioned and are associated with the SES gradient – if they

• feel they have minimal control over stressors;

• feel that they have no predictive information about the duration and intensity of the stress;

• have fewer outlets for the frustration caused by the stressor;

• interpret the stressor as evidence of circumstances worsening; and

• lack social support for the duress caused by the stressors.

An intriguing insight is that while the objective state of being poor appears to affect health adversely, the subjective state of feeling poor seems even more important. In which case, the notion of relative poverty levels becomes very relevant. Many of the stresses – such as those of inferiority feelings because of low spending power – do not go away just because of a general rise in income.

So it seems likely that the observed connection between income inequality and poor health is a stress-caused effect. The most probable channel is that the lower in the social pecking order, the more likely is it that status causes stress.

The bestseller, The Spirit Level by Richard Wilkinson and Kate Pickett, argued that for eleven different health and social problems, the outcomes are significantly worse in more unequal countries, whether rich or poor ones. They are physical health, mental health, drug abuse, education, imprisonment, obesity, social mobility, trust and community life, violence, teenage pregnancies, and child well-being.

Now a warning. The difficulty with social science research is not just that ideology can override science, but that we can rarely do research which rigorously demonstrates causality. In my experience a single observation or correlation is not enough. Instead, you build up a matrix of evidence (as I was reporting earlier). There was strong methodological criticism of The Spirit Level which I have followed up. So did Wilkinson and Pickles, as well as adding more evidence which is summarised in their new book The Inner Level.

I am almost convinced and shall proceed on the basis that this is the best theory based on the available evidence. (Incidentally I wish the critics would put forward an alternative theory; then we could compare.)

Mental Health

Since mental health is a priority in the government’s wellbeing campaign, I focus on that. Wilkinson and Pickett claim that poor mental health is more common in highly unequal countries.

They present a graph with the degree of income inequality on the horizontal axis and the percent in each country with any mental illness on the vertical axis. There is a strong trend line with most countries near it, Italy aside. That they are not exactly on it, tells us that some other things are going on. It probably includes measurement errors and other identifiable factors – for instance often the national age distribution also affects relative outcomes. 

New Zealand’s mental illness incidence (as measured by whether one has has had a mental health problem in the previous year, including minor ones) is around 22 percent of the population, which is high among the countries for which we have data, but not the highest. It appears to be high, because our income inequality is high.

This assumes that there is a causal relationship from inequality to mental illness. The Inner Level focuses on how inequality affects us individually, how it alters how we think, feel and behave. It sets out evidence that material inequities have powerful psychological effects: when the gap between rich and poor increases, so does the tendency to define and value ourselves and others in terms of superiority and inferiority; for example, low social status is associated with elevated levels of stress hormones. This suggests that rates of anxiety and depression are intimately related to the inequality where status is paramount. You cannot finish reading the book without thinking that high economic inequality is likely to be associated with poor mental health through a status-stress effect.

I should leave it there, except I cannot resist doing a rough calculation. Suppose New Zealand’s income inequality was still at the level that it was in the early 1980s. We do not have any data as to what it actually was, but if the Wilkinson and Pickett analysis is correct, the proportion of the population with mental health problems would be about a third lower – nearer to 15 percent than their figure of 22 percent. The headline finding is that it may be that one in three of our mentally ill are so as a result of the increased income inequality we experienced thirty years ago under neoliberalism.

This is a very rough calculation but the general conclusion is clear enough. Inequality appears to affect wellbeing on the mental health dimension and it seems likely that the substantial increase in inequality has led to a substantial increase in mental health. This conclusion is probably true on other dimensions of wellbeing.

There would not be an immediate major reduction in poor mental health if we were to return to the level of income inequality of the early 1980s. The problem has been evolving over decades. But to use another frequently forgotten principle, putting a fence at the top of the cliff eventually reduces the mess of ambulances at the bottom. It is a reminder that while we may have to pour resources into dealing with existing mental illness, we need to think about prevention. New Zealand is expert at shutting the stable door after the horse has bolted; of providing insufficient numbers of insufficiently equipped ambulances when the problem overwhelms it.

At this point some will say ‘think of the savings we would get from the fences. We would not have to spend as much on mental health care and there would be productivity gains in the work place together with reduced outlays because of the social damage that mental illness does.’

That may be true too, but  If the government is trying to focus on wellbeing; that there are also real output gains is an additional blessing.