Maria Puente

USA TODAY

David Cassidy's tragic family history of dementia has always haunted him; and now it's here. The former star of TV's The Partridge Family said Monday he is battling the memory-destroying brain disorder.

Cassidy's representative, Jo-Ann Geffen, confirmed to USA TODAY Monday that Cassidy, 66, has been diagnosed with dementia.

He acknowledged the diagnosis in an interview with People magazine, saying he watched his grandfather struggle with dementia and saw his mother “disappear” from it as well.

"I was in denial, but a part of me always knew this was coming," he told the magazine.

The former teen idol of the 1970s said he decided to stop touring as a musician to concentrate on his health and happiness. “I want to focus on what I am, who I am and how I’ve been without any distractions,” he says. “I want to love. I want to enjoy life.”

Cassidy is the son of a Hollywood family: His father, actor Jack Cassidy, suffered from bipolar disorder and alcoholism, and displayed increasingly erratic behavior towards the end of his life. He died in a fire in 1976 when he fell asleep with a lit cigarette. His mother, actress, Evelyn Ward, died in 2012.

Cassidy's stepmother, Shirley Jones, co-starred with her stepson in The Partridge Family, a musical sitcom based on a real family about a widow and her children who embark on a musical career as a band.

Cassidy's revelation about his health came two days after TMZ posted a video on Sunday that the gossip website claimed showed Cassidy slurring his words and forgetting lyrics in a performance near Los Angeles on Saturday night.

The website said Cassidy "seems to have fallen off the wagon," a reference to Cassidy's long struggle with substance abuse, including a stint in rehab in 2014. He said in an interview on CNN at the time that he was an alcoholic.

"If I take another drink, I'm going to die, physically, mentally, emotionally, spiritually. I'm dead," he said.

Later Monday, TMZ updated its post to add that while it may have "looked like he fell off the wagon," it wasn't that. "He says he has dementia," the site said.

Cassidy announced earlier this month on his website that he would be retiring at the end of 2017, after 49 years of concert touring.

On Feb. 7, he posted a message: "I will always be eternally grateful for the love and support you’ve shown me. I still love very much to play and perform live. But it’s much more difficult for me now. I’m not going to vanish or disappear forever."

Cassidy has had multiple arrests for drunk driving. In November 2010, he was charged with a DUI and was subsequently charged with the same offense in August 2013 and January 2014. A month after his third arrest, his wife, Sue Shifrin-Cassidy, filed for divorce.

In February 2015, the actor filed for bankruptcy. And in October 2015, he was charged following a hit-and-run crash in Fort Lauderdale, Fla., when he allegedly sideswiped a truck and then allegedly attempted to cover his license plate as he fled the scene.