These amazing Omega-3 supplements pulled me out of major episode.
Also have been trying St. John's Wort. Not sure yet if it's going to work long term but it's worth looking into.
On top of the vitamin D and getting sunlight when you can, I recommend buying a blue light similar to this one. I got one a few years ago and I use it every winter. It doesn’t permanently help but it does lessen my symptoms.
I know of only one quality book on dysthymia that's on-topic and aimed at a general audience: http://www.amazon.com/Beating-Blues-Approaches-Overcoming-Depression/dp/0195304535. It helped me immensely and I can't recommend it enough. It is a bit dated now; wish the author would write a new edition! Much of the early part of the book is devoted to describing what it's like to have dysthymia, and it was so "me" that it made me cry a couple of times.
I just clicked through and checked out The Half-Empty Heart. I had no idea it was specifically about dysthymia, but apparently, it is! I will definitely give it a read. Thanks!
I recommend the book The Half-Empty Heart: A Supportive Guide to Breaking Free from Chronic Discontent.
Give it a chance. The gist of it is that we have learned to block feelings because feelings are painful. Anytime we feel a strong emotion, we also feeling many of the similar prior emotions. We get overwhelmed and detached. We are unable to feel happy thoughts and remain empty.
Please read it. Even if it helps you just slightly any progress is good.