We are continually told that it is poverty - which of course these days means inequality - which contributes so much to mental health problems. Anything, dependent upon the person advancing the argument, from the green eyed God of jealously through to the unfairness of the distribution of resources leads to more mental health issues as the society becomes more unequal. This is rather what the Spirit Level was trying to tell us for example.

Except the actual empirical evidence seems not to be supporting that idea:

A quarter of young women in the UK have suffered from anxiety and depression, according to a new survey released by the Office for National Statistics (ONS).

...

The study also reveals that in the four years from 2009-10 to 2013-14, the number of young people saying their mental health had “deteriorated” rose from 18% to 21%.

This is all rather odd:

Other figures from the study show that the number of young people who believe they are financially comfortable has increased since 2009-10. Seven years ago, 15% said they were struggling to get by, while by 2014-15 the number reporting financial hardship was 7% – and a significantly higher percentage (45%) said they were satisfied with their household income, up from about 30% in 2009-10.

Economic conditions improve and mental health deteriorates? That's not exactly supporting the idea that it is deteriorating economic conditions which worsen mental health, is it? 

Ourselves we'd run with the idea that the two vary, except at the extremes of course, independently. For we're not in fact Marxists who believe that economics determines everything, just classical liberals who are pretty sure that economics aids in determining what happens to the economy but there's a lot more to life than merely that.