This article is about one of the mechanisms, which wasn't well known.

We know there's a bunch of reasons why poor people are unhealthy - more smoking, more alcohol, worse food, less exercise, more dangerous jobs, less protection in those dangerous jobs, less exercise, less access to health treatment (even if it's free).

But this study:

> The findings, in Science, had nothing to do with the unhealthy behaviours that are more common in poorer groups.