To be honest If you ask me, I don't believe in Depression. Why? The word depression is connected to the SUICIDE these days. Did you read the news in which a 10th standard student committed suicide, he hailed from UttarPradesh and left a suicide note which read ‘If he can do it, why can’t I?’.
Isn't it better for us to not think too much about depression or any mental illness. Because that's what makes you more ill. That's my personal thought, and trust me it works for me all the time.