Why am I depressed..?

I don't really have a complete answer to that question.. When I was 14 I came across papers that said I was adopted.. & that really messed me up.. My parents weren't fit to raise me.. They were addicted and doing all types of drugs and I was actually born addicted to crack and deaf(not deaf anymore started to hear around 2). I do think my depression is biological since drugs are depressants and I think learning that I was adopted triggered it.. 

     I've moved past the adoption part.. I understand I was blessed because I could be anywhere else right now but I'm in a economically sound family, in a nice house, on a computer, physically and mentally well.. except for the depression lol.. but my life could be so much worse than it is.. I do understand that.. but the depression is still here and that's what I don't understand. I probably  inherited a vulnerability to depression from one of my "parents", that my  brain may have reacted to a stressful event(finding out I'm adopted) in a way that caused me to get depressed. I read that in adopted children I have three times the risk of having depression.. so that might explain a lot. 
    Hopefully soon I'll be on antidepressants and things will go back to the way they were and I can be called a survivor.. But for now I'm just making it one day at a time.
This post deserved a picture...

 Even though the light at the end of the tunnel may not be visible.. it's there, just hold on. We can walk there together.