Do writers have more self-doubt than professionals in other fields?

According to Sylvia Plath, “The worst enemy to creativity is self-doubt.” Even great writers, such as Virginia Woolf or Anne Frank, have been known to express recurring doubts about the quality of their work. I believe that this self-consciousness is one of the core causes of “writer’s block”. The fact that the problem has a name is a good indicator of just how common it is. Is the inability to work effectively due to self-doubt more common among writers and artists than people in trades or professional positions like health care or auto repair? After all, you don’t often hear an auto mechanic say, “I just can’t work on this car. I’ve got mechanic’s block”. Are writers and people in artistic disciplines more prone to second-guessing their abilities than people in more strictly practical fields? If so, then why?