I look at depression as a state of mind so trauma and bad memories are first to cause depression, failures and criticsm also comes next and last is being introvert or a safe way to say is that most depressed people are being more and more depressed because they cannot let the feeling out. The are afraid to share the situation and are afraid to be judged. So to us who is not depressed a moment let us try to help someone by talking and listening to them.