Taking alone the three keywords from the heading of your post: Ontology – social causation – mental illness.
- There are different types of mental illness, see ICD-10.
- There are diffent social environments.
- And during the history of philosophy different ontologies have been proposed and investigated.
At least, any hypothesis on this field should clarify:
Which mental disturbance is caused or inforced also by which social environment, and to which degree in comparison to other causal factors?
I assume that you mean by “ruling ontology” in your post simply an influential thesis in social science or psychology.
In order to assess Fisher’s thesis it would be helpful if you could provide some of his arguments, which you find convincing. And also some counter-arguments against those which do not seem so.
Otherwise the gap is too wide to link depression with the level of politics or philosophy.