Patrick Kennedy in 2011, after launching One Mind for Research to improve funding and unify efforts in brain science . (Steven Senne/Associated Press)

Updated 10 a.m.

For a generation of liberals, legalization of marijuana has become a harmless — if not inevitable — issue.

Not for Patrick Kennedy. The former Rhode Island congressman and scion of the famed Democratic dynasty has taken a surprising turn to the right in this debate.

“Marijuana destroys the brain and expedites psychosis,” he told us Tuesday. “It’s just overall a very dangerous drug.”

Kennedy’s public battles with alcohol and prescription drugs are well known. Was pot an issue for him? He’s used it but wouldn’t elaborate. Still, it’s all part of the same conversation for him: “In terms of neurobiology, there’s no distinction between the quality and types of drugs that people get addicted to. That’s why they call it a gateway drug. Addiction is addiction is addiction.”

Supporters attending an Amendment 64 watch party last November celebrate after the marijuana amendment's passage, which made it legal in Colorado for individuals to possess marijuana for recreational use. (Brennan Linsley/AP)

After 16 years in Congress, Kennedy, 45, left Washington two years ago and began traveling the country to see how legislation he spearheaded on mental health is being implemented. He’s become convinced that marijuana (“the biggest single threat to the cause I care so much about”) is as destructive as alcohol and tobacco and just launched Project SAM (Smart Approaches to Marijuana) to shift the debate from legalization to prevention and treatment — despite what appears to be a growing social acceptance of the drug.

A passionate Kennedy cited his years researching mental health issues in Congress, consulting with experts in the field and his own experiences in rehab.

“I’m not just a casual bystander,” he said. “I’m ready to stake my reputation. I still consider myself having a public responsibility. The weight of evidence is so overwhelming that I don’t think it’s responsible not to speak out on this.”

There’s a personal reason, too: Kennedy, who married for the first time in 2011, has an 8-month-old son and said he’s worried about a family propensity to addiction and increased access to drugs if marijuana use is widely accepted.

Kennedy’s partners in the cause include Kevin Sabet, a former drug-policy advisor in the Obama administration, who noted that the group would like to see reforms to the current laws: Young people cited for marijuana use shouldn’t necessarily have their records permanently stained by it. Conservative commentator David Frum has joined Project SAM’s board; he said he fears legalization would create another Big Tobacco — “an industry with a vested interest in encouraging more use.”

News of Kennedy’s cause drew fast and furious criticism from the Marijuana Policy Project. “If Mr. Kennedy is truly concerned about public health and safety, I cannot fathom why he would prefer that adults use alcohol instead of making the safer choice of marijuana,” said spokesman Mason Tvert, who successfully led November’s Colorado initiative to legalize small amounts of pot for personal use.

Project SAM kicks off Thursday in Denver — no coincidence there— and Kennedy will come to D.C. on Jan. 18 to help promote his cousin Christopher Kennedy Lawford’s new book, “Recover to Live: Kick Any Habit, Manage Any Addiction.”

Kennedy told us he’ll be happy just starting a debate among his liberal friends: “If I can get people to think twice about this, that would be a win for me.”

10 a.m. Wednesday: This story has been expanded and updated.

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Earlier: Patrick Kennedy discusses leaving Congress after 16 years, 3/12/10 

Patrick Kennedy talks mental health (video), 10/5/12

Love, etc.: Patrick Kennedy welcomes baby boy, 4/16/12

Love, etc.: Patrick Kennedy marries Amy Petitgout, 7/16/11

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