This is a very interesting question. I definitely think it's possible. However, I can understand why there might be a tendency for individuals with mental disorders to bond more frequently with others who have mental disorders. Similar-ish experiences of any sort, I think, can make people relate to one another more.

Also, I don't necessarily think someone who has been diagnosed with a mental disorder is always mentally unhealthy. They may have been and aren't any more, or they could go back and forth. In either case, dating someone with a mental disorder could potentially be just as rewarding as dating someone who doesn't, but that's just my personal view.

Best of luck to you.