Cory Monteith empathises with "marginalised" young people because of his own difficult teen years.
The 'Glee' star - who admits he had a "serious problem" with drugs in his teens - recently visited a centre for homeless people in the UK and admits it made him feel "humble" sharing their experiences.
The Canadian-born actor told The Sun newspaper: "I was a troubled kid. Although I was never homeless myself, I was marginalised. Meeting some of the people here makes me feel very humble.
"I feel fortunate that I had the support around so that I was able to overcome a lot of the difficulties I was dealing with.
"The reason I talk about my past is not to seem opportunistic, but to raise awareness that these problems exist for young people. A lot of people have come from marginalised situations."
Cory - who plays Finn Hudson in the musical TV show - is shocked that people can still find themselves in such circumstances in the developed world.
He added: "It's not hard to believe that this happened to someone on TV. It's hard to believe there are still such problems in First World countries."
Cory's own struggles saw him start drinking and smoking marijuana at the age of 13 before dropping out of school at 16 and starting to use harder drugs, taking "anything and everything.
His family intervened when he was 19, and he was able to turn his life around, something he is eternally grateful for.
Cory, now 29, has previously said: "I don't want kids to think it's OK to drop out of school and get high, and they'll be famous actors, too.
"But for those people who might give up: Get real about what you want and go after it. If I can, anyone can."