I do believe that it effects we fiction writer's more. Non-fiction writers can be effected as well, but not in the same way as fiction writers. I believe it's because of the fact that so much of what the fiction writer conjures up is from our abitity to use our Imaginations and Dream up new and strange things.
It's hard to come up with something that hasn't been done before that will lure readers or viewers in and keep them coming back for more. This isn't the case for Non-fiction writers. While they may face the same demons when it comes to hooking an audience their writing comes from Facts or True Stories. They don't have to invent whole persons, places or things, they have other means inwhich to be creative.
So, Yes I do believe that writers block does effect Fiction writers more than Non-fiction writers and thanks for this great question.