Since I went Paleo and then Paleo-ketogenic, I'm always happy, and there are times that I feel naturally high (starting laughing like a maniac, but in a good way). My brain chemistry has really changed since I changed my diet, I have no situational depression anymore either.

UPDATE: A month after I wrote the answer above, I had more info on my hands, and I wrote a blog post about the ketogenic euphoria/bliss people under ketosis are often experiencing: http://eugenia.queru.com/2012/03/07/bliss/

Since I went Paleo and then Paleo-ketogenic, I'm always happy, and there are times that I feel naturally high (starting laughing like a maniac, but in a good way). My brain chemistry has really changed since I changed my diet, I have no situational depression anymore either.