There’s quite some research around on empathy and/or “Theory of Mind” ((ToM): the ability to grasp another’s mental states) in schizophrenia. A quick search yielded: http://www.ncbi.nlm.nih.gov/pubmed/18514324, http://www.ncbi.nlm.nih.gov/pubmed/18514324, and a meta-analysis http://www.schres-journal.com/article/S0920-9964(16)30129-3/abstract?rss=yes, to name a few. The results are pretty consistent: most research indicates impaired empathic/ToM abilities in schizophrenia sufferers.
Such may partially account for some felt distance from people without mental illness. But it is clearly not the whole story, it seems to me. I came across an article that centred on the other direction of encounters between those with and those without a mental illness. The (from both parties) felt lack of understanding of those with, by those without mentall illness. I think we can all relate to the feeling, I certainly can, that ordinary healthy people don’t understand us, and all too often, they might readily agree to that. The latter would, in the technical sense of the terms, be a failure of empathy/ToM on behalf of the non-mentally ill.
Then there’s the fourth possible encounter (taking for granted encounters among those without mental illness), namely those among several patients with mental illness, like us interacting here on the forum, to some extent. And here all of a sudden, it seems, empathy resurfaces again as being actually achieved, and maybe some sense of recognition or even belonging may be found.
These three kinds of encounters taken in consideration together, if portrayed accurately, pose a bit of a puzzle to the empathy-impairment hypothesis present in the research referenced. The article I came across, while focusing on the misunderstanding of those with mental illness by those without, argues for a slightly different concept/definition of empathy than is taken for granted in the research, but which can account for said puzzle. Aside from that, I think that especially the first few pages are very sensitively written.