“The Synanon Fix,” Rory Kennedy’s latest documentary, is a full-on immersion in the 30-plus years that were defined by Synanon’s promising rise and terrible fall.

It began in 1958 as a landmark breakthrough in the treatment of heroin addicts, confrontational therapy they called ‘The Synanon Game.’

Instead of demonizing addicts, Synanon saw them, like alcoholics in AA, as people who could learn sobriety. Synanon expanded to other states and cities and became national news. There was even “Synanon,” a 1965 Hollywood movie with Chuck Connors and Stella Stevens.

Funded by donations with a tax-exempt status, Synanon thrived until in the ‘70s its founder Charles “Chuck” Dederich became essentially a cult leader, dictatorial, paranoid and eventually charged with child abuse and attempted murder.

Producer-director Kennedy and her husband and producing partner Mark Bailey, who also is a co-writer, gained remarkable access to years of archival material for this four-part history that includes contemporary reflections, reactions and insight from past members.

“We started talking about this project four and a half years ago with HBO,” Kennedy, 55, began in a Zoom interview. “Part of our development process was, ‘Can we explore the Synanon Archive’?

“We came to understand pretty quickly that there was a lot of Archive but that the Synanon Trust owned it and they were not, at that point, willing to share it. And they documented a lot!”

She discovered that the many Synanons in various cities and locales were connected with The Wire, their communication system. Dederich and everyone else who spoke on The Wire were constantly recorded  — as were virtually nonstop video recordings of every kind of Synanon activity.

“Outside the Synanon Archive a number of artists who went through Synanon took their own photos and videos and we had those,” Kennedy said.  “But the Synanon Archive was the biggest.

“Chuck’s daughter, JD was a trustee along with a few others. I don’t like to speak for other people but I’m pretty comfortable in summarizing that she felt that Synanon, even though it did a lot of great things, it did a lot of damage to a lot of people.

“And she didn’t want the Archive being used in a way that could cause more damage or be more hurtful to anybody. We came to terms to make her comfortable.

“Then just three weeks before we were to ‘lock picture’ on the series, the Archive gave us the green light.

“That was really a breakthrough for us. We then had to go back to HBO to ask, ‘Can we go through all this Archive that’s now available to us?’

“They were enormously supportive and gave us the time that we needed to integrate this massive amount of material into the film.”

“The Synanon Fix” airs on HBO April 1 and will be available to stream on Max. New episodes debuting subsequent Mondays

Rory Kennedy attends the Los Angeles Premiere of “The Synanon Fix” last week in Santa Monica, California. (Photo by Jon Kopaloff/Getty Images for HBO)