Actually, having worked at the Center for Poverty, Risk, and Mental Health throughout the 1990s, I can tell you that mental health is a byproduct of money, in part. There is something called the health gradient. It has been one of the most consistent correlations in medicine since the early 1900s. There are numerous articles on this, but this one discusses how income inequality does not affect mental illness, but individual income strongly does: http://icmpe.org/test1/journal/issues/v4pdf/4-197_text.pdf

This is another source, but unfortunately, you can’t access it without being connected to a college, which you may be. It does provide a good overview on its first page, however: http://epirev.oxfordjournals.org/content/26/1/53.short