dear Ashrose, welcome to this site, there are plenty of different people here all with different points of view, and someone will click with you.
Depression doesn't only occur simply by someone passing away, nor by another event going wrong, or though these could be the reason, however, what it does to you, me and all the people is bring despair, misery, feeling of being negative, destroys relationships and affects our desire to not want to work or study.
It can come on for no reason at all, happy yesterday, but next day we are depressed, and we don't know why, and no circumstances can explain it.
I hope that you can get back to us and explain just a little more, to see if we can help you, but more so to make you feel comfortable. Take care. Geoff.