I have a interdisciplinary PhD (media arts and technology). Personally, I think any PhD could pull from multiple disciplines and, really, most dissertations must to some extent. If you are doing something new in your field, you need to at least check what is relevant in other fields.

It’s good to know interdisciplinary programs are an option, and I wish I knew sooner, but I’d recommend joining one only if there’s a good reason. In other words, I’d suggest looking into a more typical program by default. The reason is that you will have to work with established disciplines at some point. For teaching positions, you will probably need to demonstrate both that you can do innovative research (thus the requirement of a dissertation) and that you can teach more broadly. And just generally, academics are actually pretty conservative as a whole, so you’ll have to fit your research into their view. Having a PhD in an established discipline just makes it easier to do that.

But the programs are still useful. For me, it would have been pretty difficult to get into a music or art program based on my past studies and work. I wouldn’t necessarily plan on doing that from the start though, because I could have studied music and engineering (for example) from my undergraduate degree onward.