Broaden and build theory

The broaden and build theory discusses the following; happiness predisposes us to think more openly, allowing us to see the "big picture" we might have otherwise overlooked. They tested this theory by using candy and doctors. Doctors who received a candy bag made more accurate diagnoses on patients with liver diseases than doctors who didn't have any candy. While the book didn't go into detail about the study, for all intents and purposes we will assume that the study was done with equally competent doctors on both parties and that the candy made them noticeably happier. I can believe this hypothesis. I will go as far to say that the happier I am the more clearly I can think and project my thoughts more clearly and with more ease than I would be able to if I would be unhappy or under any kinds of stress. I'm not saying that someone can't be a depressed genius, but I think someone is more capable if they are happy. That may be because they see more of a point to it, or just because that is how our brain is wired. Your thoughts?