I think it can be a source of inspiration, but I also have days when it takes a lot of effort to just hold conversation because I'm so mentally drained. When I feel good mentally, I'm a lot more productive and level-headed. It might take more effort to get in touch with intense emotions in order to make creative stuff, but after that being creative is a lot more organised and for-filling. It's easier to persist when I hit a wall and the end result is often more well-rounded.
I think mental illness can enhance creativity sometimes, but it's not really worth it.