How can isolated living impact a person?

In school, my cl is doing a unit on Edgar Allen Poe. For some of his life, he was isolated and he lived by himself. I am supposed to find a website (it doesn't have to be about Edgar Allen Poe) that explains how isolated living can impact a person. I have searched every place I can think of, but I can't find anything. One example would be life as a hermit. Even the slightest help would be appreciated. Thanks!