Can I use downloaded photoshop brushes in a book Im going to publish?

[yarjarrar]

Hi, I'm making a comic book which is all done in photoshop, and I downloaded some photoshop brushes that would be useful. When I'll finish the comic book, I'm going to be publishing it, and copywriting it and all that jazz. So I'm wondering if I may use these brushes I downloaded, in my book.

 

[TheAngusBurger]

I'd imagine that you'd need the creator's permission before you can use them for anything commercial.