Before you go to a pill doctor, try eliminating sugar and refined flour from your diet. Sugar can really be a bully emotionally. Also, caffeine can drag you down. We have started a support group in the Personal Growth forum for those of us that need a little encouragement to give up the coffee.
I agree with those who posted exercise and sunshine. Also, drink lots of water. Dehydration can be a cause of depression.
Take some time for yourself to meditate and clear your mind each day. Don't dwell on the negative. You will attract negativity to you.