I used to have a friend who suffered from major depressive disorder (MDD) before. At that time, she was really depressed like everything in her world was crumbled and shattered. She told me that she suffered but she didn't know why and what, she even had the idea of committing suicide. Everyone told her that she think too much but it's not, it's a disorder from abnormal neurotransmitter. Several months after treatment, her mental was better. So if you have friends who being MDD, please understood them and take them to see doctor before it's too late.