As could be expected, Sean Astin is approached often by strangers. What may be surprising, however, is that not all of them want to talk about the actor's roles in the epic "The Lord of the Rings" trilogy or his early work on the '80s classic "The Goonies."

Instead, many want to discuss his very public mother, Patty Duke, and her very public battle with bipolar disorder.

From a clerk at an airport gift shop to a makeup artist hired for a series of appearances in Salt Lake City, they say they have been affected in some way by the mental illness.

"Everywhere I go, people say that they've been touched by it," the 35-year-old Astin said, stopping in Utah as part of a public-awareness campaign about bipolar disorder, also called manic depression. "People are whispering less about it."

Astin spoke candidly Wednesday about life with Duke, who began having symptoms when she was in her late teens and early 20s.

"Our life was intensely impacted by her mood swings," he said.

Astin's family — which included his father, John Astin, famous for his role as Gomez on "The Addams Family" TV series, a younger brother and three older half brothers — called Duke's manic episodes "freak-outs." During these times, Astin said, his mother would scream, yell, throw and break things. Once, he remembered, she purposely drove her car into the front of the garage.

"What I know, from a family member's experience: It was painful, it was excruciating, to watch her suffer."

According to the National Alliance for the Mentally Ill, bipolar disorder affects 2.3 million adult Americans, about 1.2 percent of the nation's population. Sheri Wittwer, executive director of NAMI UTAH, praised the work that Astin and Duke have done to raise the level of awareness about bipolar disorder, a brain disorder that causes extreme shifts in mood, energy and functioning.

"We always appreciate when we have celebrities who are willing to put a name and a face to these illnesses," Wittwer said. "To show that you can live a very successful, productive life and have a mental illness. It's a part of your life, but instead of seeing the illness, we see people who are overcoming challenges and who are accomplishing tremendous things."

The campaign is sponsored by AstraZeneca, a pharmaceutical company that makes Seroquel, a drug used to treat schizophrenia and bipolar disorder. Still, Astin said, it was important to him that the campaign be about overall awareness rather than any particular drug.

"I've really looked with a critical eye in terms of how this awareness campaign was being approached," he said.

Duke's manic episodes continued for much of Astin's childhood. He has since learned that ongoing difficulties are not unique to his mother's situation. Studies have shown that a person with bipolar disorder will often suffer serious symptoms for 10 or more years before an accurate diagnosis and treatment plan is made.