Michael Douglas says he couldn't help thinking about the troubled pasts of those close to him — including his half-brother, Eric, and his son,

Cameron — while playing the father of a drug-addicted daughter in Traffic (opening wide on Jan. 5).

"A lot of people came to mind, both family and friends," the actor tells TV Guide Online, noting that one particularly intense scene in which he confronts his daughter (played by Erika Christensen) about her drug use was eerily reminiscent of his own problems with Cameron. "In any role, you try to bring [in] your own personal experiences."

Douglas is happy to report that 20-year-old Cameron — whose past drug exploits made him a familiar face in the supermarket tabloids — is "doing great. For me, the fact that my son doesn't have the ability to make mistakes out of the public eye is one of the most unfortunate aspects of celebrity-dom. You wouldn't wish that on any of your own children."

The proud papa was particularly pleased to have his son beside him during his recent wedding to actress Catherine Zeta-Jones. "When I came down the aisle with Cameron, everyone broke into applause," he says. The younger Douglas even provided a light-hearted toast to the happy couple. "We were kind of touched and overwhelmed. The joy on Cameron's face for how happy he was for his dad meant a lot."

Douglas also weighs in on the substance abuse problems of Robert Downey, Jr., who was to have starred opposite Zeta-Jones in the upcoming comedy America's Sweethearts. "My heart goes out to him," he says. "I think everybody really is fond of him, personally, and I do think he is one of the best actors of his generation. The frustration about the waste is what both hurts you and makes you angry."