Hello tamilse: Well... the Skeezyks is certainly no expert with regard to the causes of depression.

But I believe the current thinking is that depression is caused by neurochemical imbalances in the brain. And, of course, life experiences can contribute to the development of depression as well... such as the death of a loved one, physical & / or emotional abuse, & other things.
I see this is your first post here on PC. So... welcome to PsychCentral… from the Skeezyks!

I hope you find the time you spend here to be of benefit.
PsychCentral is a great place to get information as well as support for mental health issues. There are many knowledgeable & caring members here. The more you post, & reply to other members’ posts, the more a part of the community you will become.

Plus there are social groups you can join & chat rooms where you’ll be able to connect with other PC members in real time (once your first 5 posts have been reviewed & approved.) Lots of great stuff! So please keep posting!