David Sheff says he was in denial about the extent of his drug addiction.

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David says he knew his son was in trouble, but he was in denial about the extent of his addiction. "I kind of think we parents are wired for denial because to see the trouble that our child is in is so painful. It's so terrifying," he says. "I would hear the good things; I'd see the good things. I'd block out the terrifying course that we were on until it was impossible to deny anymore."

When Nic began skipping classes in high school, David says he spoke to teachers and a counselor about his rebellious behavior. "[They said], 'Nic's fine. He's a smart kid. He's doing fine. He's doing well in school,'" David says. "It wasn't that I completely dismissed it. I was worried. [But] I didn't take it seriously."

The counselor also told David college would straighten Nic out. "Did I believe it?" he says. "I wanted to believe it." Nic enrolled at the University of California, Berkeley, but he didn't make it through his freshman year.

In an attempt to protect his son and himself, David says he hid Nic's addiction from friends and family at first. "I didn't want them to think badly of my son," he says. "I was ashamed. My son is a drug addict. What does this mean about me?"