If you are in depression, do continue your regular treatment and anti-depressants till the docs allow you to stop. Once you are treated, then mindfulness/ being in the Now, can move you to happiness and freedom. I say this because no one (I've read) has said this cures depression. And the root of depression can be bio-chemical. However, in the long run, you would give up medication (hopefully in a year), and then the "present moment" is the key. The beauty is that is becomes easy and natural after a while. If you've suffered (been unhappy) then you have the motivation not to give up, to take this through to completion.

Go through Eckhart Tolle and Mooji (on youtube). "Power of Now" is good. Start this moment.