Toi: And I am saying that that that is a false assumption based on a lack of data and no small amount of undue prejudice.
Obviously I am not interested in marrying someone who would attack people with meat cleavers. I would not, however, write off someone with an emotional or mental disorder as potentially homicidal. For one–if I did so, I would have to write off the rest of humanity as well, since every last one of them has the potential to become mentally ill.
Also, I am not trying to say that I would totally be okay with any sort of illness at any stage of treatment. Some mental illnesses have more serious implications. The OP specifically asked about depression, to which I responded that it would depend on the circumstances surrounding the depression and how it was being/had been handled. Other illnesses, especially ongoing, would definitely give me more pause.