You are correct. I believe there are many variables at play. There is certainly such a thing as mental illness but community and social context, isolation or cohesiveness etc. play a huge part also. 
In Canadian big cities we have had tremendous cultural upheaval with heavy doses of social engineering. I don't believe it has been good for mental health in general. In short, community and societal context can help prevent or exacerbate mental health issues. Which is something they don't really address; as if people are just some in vitro specimen.