I personally was born in an environment where many people were stressed and caught onto depression. Even so, few people knew about it. It was an unhealthy state at the time. I was interested so I went to ask my family doctor where I learnt a lot. There are so many websites online that teach about the dramatic causes of this disease including this website. Some of my close friends have depression too. Although 50% of the world the world does not get affected by this many people still do. It can be common. That's how i learnt about depression.