Transcript for Robin Williams' Battle With Depression, While Bringing Others Joy
Tonight investigators have not revealed whether there was a note left behind or any message for his family, his three children. His family knew of his struggles. Robin Williams had acknowledged his marriages had paid the price, and he was very candid with Diane sawyer about addiction after a stint in rehab in 2006, about the constant voice he heard, the temptation, and the new hope when he got out. Here's ABC's juju Chang. Reporter: Like many performers robin Williams used drugs and alcohol in his comedy on stage and off stage as well. Then in 1982 an overdose killed his chose friend, John belushi. They reportedly partied together that night. That inspired him to go cold Turkey, no rehab. He said he was clean nearly two decades, until he relapsed and wound up in rehab for the first time. Diane sawyer interviewed him in 2006 when he was still counting sobriety in months, not years. Two months, club medicated, quiet time. I'm back. People say how do you feel? With my fingers. Don't drink. What are you doing to stay that way, don't drink. Was there something somebody said to you that got through --? You're a drunk? You got to get help. You got to go away and deal with this. Family, friends? Many people. It was unanimous on that level. And you go you're right. It takes a lot to finally realize it and you say, got to go. And then you go and you go, yeah. Then the moment you start to deal with it you go whoa, wow. And then you come out of it. And then you have to go back and go, okay, this is what I've done and everyone says you're so brave. It wasn't brave. You have no choice. You do have a choice. You can keep going over the edge. How hard was it to talk to your kids, your wife? They're very supportive. It's not hard. It's hard admitting it. Then once you've done that, it's real easy. It's trying to keep up the pretense. The sad thing for most people is you think that people don't notice. You find out later on, we knew. Even the dog is like, woof woof. What have they said to you through this? That they love me, which is great. That's the simplest, most wonderful thing. How long before you decided this is it? I don't know. It was a couple of years of just thinking I can do it on my own, and you can't. That's the bottom line. I can do this, I can stop, and you really think you can, and then you realize, I need help. And that's the operative word. So to talk about it as caused by something -- It's not caused by anything. It's just there. Latent. Waits. It lays in wait for the time when you think, it's fine now, I'm okay, and then, beep, and then the next thing you know, it's not okay. It's not going so well. And then you realize where am I? This is strange. I didn't realize I was in Cleveland. You're standing at a precipice and you look down and there's a little quiet voice that goes, yeah, it's the same voice that says you can do this, you can jump. You can fly. And the idea of just one, for someone who has no tolerance for it, it's not a possibility. Reporter: It was that voice he said that encouraged him to take a drink of whiskey in 2006. Within a week he was in trouble. Just last month, another trip to rehab for the comedian. Williams described his addictions as an escape. We may now know from what. His representative says the comic and actor was in the grip of a severe depression. ABC news contributor Dr. Jennifer Ashton says addiction can fuel depression and vice-versa. Why does it frequently go hand in hand? It's kind of which came first, the chicken offer tr the egg. Does substance abuse lead to addiction or does addiction lead to depression. The answer is it really can go in both directions. Reporter: The irony of a master of laughter enslaved in darkness is to striking. Could there be a connection there as well? He was so eloquent in describing addiction and inspired people. Depression and addiction does not discriminate. It doesn't care whether you have an Oscar. It doesn't care whether you have a lot of money and it doesn't care whether you're homeless. Reporter: Comedian Jim carry said he, too, struggled with depression, describing it as a low level of compare. Comedian chevy chase said robin and I were great friends, suffering from the same, little known disease, depression. Lady gaga tweeted, perhaps this tragedy will shed light on the seriousness of depression and urged followers by saying, if you are struggling with depression, mental illness or addiction, you are not alone. I understand the pain you're all going through. Reporter: Actress Lisa Jacob who played Williams' daughter in "Mrs. Doubtfire" posted a farewell letter, saying she herself suffered from depression. It's real and it's not shameful and there is help available. Alcohol is dangerous for people like myself, alcoholics. Reporter: In that candid conversation with Diane, the word depression never came up, but Williams sounded hopeful. Is there a sadness about these past two years then? Yeah, there's a sadness, and then you have to go with there's also hope. Sadness is almost like, yeah, you wish that hadn't happened but it did. And the purpose is to make you different. It's what they call a buddhist gift. I would call it the ultimate Christian gift. It's that idea of you're back and you realize the thing that matters are others way beyond yourself. Self goes away. Ego, bye-bye. You realize there are a lot of amazing people out there to be grateful for, and a loving god. Other than that, good luck. That's what life is about.
This transcript has been automatically generated and may not be 100% accurate.