How can a friend or family member try to help someone with depression?

Anonymous
Last night, I went out of my room to get something, and when I came back, I overheard my sister and my best friend talking about how they both think they suffer from clinical depression. I have suspected this from both of them for a while but when it got serious I calmed them down and they never committed suicide. At this point, I don't think its right to just leave it at that anymore. My best friend thinks she can't talk to me about it, but she can. How can I try to help them?
How can a friend or family member try to help someone with depression?
3 Opinion