Sister Morphine

I'm reading this book at the moment, by Catherine Eisner, published by Salt. If anyone else has read it, please can you explain why Salt call it a "novel" rather than a collection of short stories? I don't see how it can be a novel, as it consists of individual 'case studies' of women with mental health issues. I have read about a third of the way through so far, and there is no connecting thread between the individual accounts, or none that I can see. I know there is sometimes a stigma associated with selling short story collections (and this is a debut collection), but since Salt is a great champion of the short story, I can't think they would fall into the trap of believing readers would be put off by the tag 'short stories'.

Please don't misunderstand - I'm enjoying what I've read so far (although I do feel some of the stories are over-written and the individual voices don't always shine through). I just don't see it is as a novel, and wonder why Salt do.