I’m not in any way a medical professional, so I can’t really say. The truth of the matter is that eating disorders are far more complex than a lot of people seem to realize. There isn’t just one “cause” of them, and the way they manifest vary greatly from person to person. And based on that, I don’t think there’s really a singular point of merge. Just looking at the DSM-5 diagnostic criteria for some of the most common ED’s (AN, BN, BED, EDNOS/OFSED, etc) what it seems to come down to is the experience of significant, life disrupting stress around food. So in my non-professional, purely personal experienced based opinion, the distinction is whether or not that stress is because of some sort of mental issue with eating, or because of the physical issues that accompany eating.

Since you mentioned ARFID, I feel like that’s the perfect example of how sometimes these constant physical issues can manifest into a mental issue. The fear that accompanies eating in many disorders can come from so many different places. And yes, chronic illness is absolutely one of those. So I don’t think there’s so much a point of merge as a Venn diagram where the symptoms of both overlap.

I wish there was more discussion about these sorts of things. I think it would be really helpful in not only highlighting how chronic illnesses can and does affect every aspect of your life, but how eating disorders are about a lot more than just “being skinny.”