Assuming there's no organic cause, why not try looking at self-help books? I found the following useful:
http://www.amazon.com/Happiness-Trap-Struggling-Start-Living...
Ask HN: Depression, Loss of Motivation, Feeling Lost. Please Help
51–53 of 53 posts
Re: Ask HN: Depression, Loss of Motivation, Feeling Lost. Please Help
#52A couple of things: 1. I was in a similar state, and found out I had hyperthyroidism. Thyroid now removed, I'm much better, but there are many other such conditions that can be causing things that you might not have all the tools yourself to work out, so check with a doctor or your school's nurse at the very least. 2. Caffeine screws most people I know up. It's very fun and useful, and I don't recognize myself withou…
Somewhat related to #1 is vitamin D deficiency. Don't fall in the trap of dismissing it because it's "just a vitamin" (which it actually isn't), because a severe deficiency will screw you up good. Pretty much everyone is deficient, but the severity varies. Geeks who spend most of their time indoors, staying late up at night working on stuff are more at risk. Don't assume that drinking a lot of fortified milk/whatever…
Thank you for posting this. I have a friend who is after a year or more finally getting sort of back to normal after a vitamin D deficiency.
Re: Ask HN: Depression, Loss of Motivation, Feeling Lost. Please Help
#53Television and computers fool our brain into thinking that it is active, but give it none of the rewards of actually taking action and either failing or succeeding.
Boycott television and don't use the computer or iPod for a day. Do what you feel like doing, as long as you are actually doing something, not simply consuming media.