DiVerde, 34, was last seen walking away from the El Dorado Center in Live Oak on July 8, Santa Cruz County sheriff's Sgt. Dan Campos said.
His mother, Pam Campbell, reported DiVerde missing on Friday after he failed to call her on a toll-free number she had set up for him to routinely check in with her.
"I normally saw him every week, I would go down there to take him body boarding," Campbell said. "I would talk to him every other day if not every day. The last time I saw him he was real depressed."
Shortly thereafter "he walked away from a treatment center. I haven't heard from him in four months," she said.
DiVerde suffers from bipolar disorder, drug problems and has shown schizophrenic behavior, Campbell said.
"We consider him at risk," Campos said.
Sheriff's department search teams looked for DiVerde in the Pogonip Park area in Santa Cruz today on a report that he had been spotted there as recently as Friday, Campos said.
"It's a roll of the dice where he might be," Campos said.
DiVerde is described as a white man about 6 feet, 2 inches tall and weighing 185 pounds. He was last seen with a Fu Manch-style mustache, Campos said.
DiVerde played football at Mountain View High School, where a football injury to his head during his junior year may have lead to his mental illness, Campbell said.
"I think it brought it on," Campbell said of the injury. She added that mental illness "runs in my family."
DiVerde moved to Santa Cruz to attend Cabrillo College 14 years ago, Campbell said. He attended Castro Elementary School, Graham Middle School and Mountain View High School.
DiVerde has been arrested before on charges of battery and resisting arrest. Anyone with information is asked to call either 911, sheriff's office dispatch at (831) 471-1121 or the investigations unit at (831) 454-2311. Campbell can be reached at 800-983-1706.
Bay City News contributed to this report.