what is depression and why even Christians experience it?

Again, a message a bit different! In my desire to educate who are willing to come and listen, i go deep into finding useful information and then i am sharing them with you!
This is what we should do always! To educate ourselves and then eachother ! Knowledge makes us powerful! God is the one that endowed you with a brain and He expects you to use it, Ask the LIGHT that comes from the Holy Spirit to make you understand!
So, lets analyze depression and why Christians as well, experience it!
As a bible reference will give this
psalm 42:11

Why are you in despair, O my soul? And why have you become disturbed within me? Hope in God, for I shall yet praise Him, The help of my countenance and my God.

Thank you so much