It is the only possible explanation for what happens in the direct-to-video movie Pooh's Grand Adventure: The Search for Christopher Robin. The end of the movie reveals that all of the frightening things that Pooh and his friends encountered while they were looking for Christopher Robin really weren't that scary at all (the "giant cliff" that they actually fell into was just a few inches high, for example). This would imply that either they were all having the same hallucination or that the forest itself changes in response to their expectations. They were afraid, and so the forest became more frightening. This also explains how their journey out was so much longer than the one back.