The 57-year-old — who was diagnosed with bipolar disorder at 22 years old — was prescribed lithium, a “wonder drug” he would take on and off, leading to manic episodes, he writes in his new memoir, “Nothing General About It: How Love (and Lithium) Saved Me On and Off General Hospital.”

In 1993, Benard was off his medication and just two weeks into playing leading man Sonny Corinthos on “General Hospital” when he “began hearing voices when no one was in the room with me. I heard them on set, in the car, and at home.”

The manic episode culminated in a breakdown one night at home, during which he threatened to kill his wife, Paula, and her two young nieces who were staying with them, he writes.

“I walked around the house and played Michael Jackson’s song ‘Man in the Mirror’ over and over,” Benard writes. “I thought I had a unique connection to Michael Jackson because, off my meds, my mind convinced me that Michael Jackson was singing about me.”

At that point, Paula frantically called Benard’s doctor, who prescribed a tranquilizer. Before she could get him to take it, Benard says he ran over to a nearby friend’s house and began yelling at his friend’s wife, “Devil, get out!”

Following the episode, “General Hospital” gave the star two weeks off to recover, he writes. He attended therapy and went back on lithium.

He writes that going back to work “was the hardest thing I have ever done in my life” and burst into tears on-set, even saying he wanted to quit. “They were the most gracious and kind producers in the world and that is something for which I will always be grateful.”

Benard, who is still playing Corinthos and has earned two Daytime Emmy Awards for the role over the years, revealed his diagnosis to the public in 2000 and is now a spokesperson for Mental Health America.

Despite it being 27 years since his last breakdown, Benard, who now shares four children with his wife, says he still suffers from anxiety.

“I do wake up some mornings with that knot in my stomach, that dread for no apparent reason engulfing me, and I still fight the anxiety demon that I will most likely fight the rest of my life,” he writes in the book. “It’s a pain in my ass, but I’ve accepted that’s just the way it is.”

He says he maintains mental stability through medication, exercise and meditating.