Feb. 4, 2014 -- After more than two decades of sobriety, Oscar-winning actor Philip Seymour Hoffman was found inside his New York City apartment on Sunday, police said, with a needle stuck in his arm, dead from a possible heroin overdose.
Even with 23 years of abstinence under his belt, experts say that it's not all that surprising Hoffman fell off the wagon.
"We treat addiction like you can make it go away with a 28-day stint in rehab and that's the end of it, but that's not how it works," said Dr. Joseph Shrand, a Harvard professor and the medical director of CASTLE, a teen addiction treatment center in Brockton, Mass. "It requires lifelong vigilance to stay clean."
Research suggests that the chance of relapse does diminish over time but always remains a possibility.
One analysis funded by National Institutes on Drug Abuse found that between 25 percent and 50 percent of substance users resume drug or alcohol use within 2 years after finishing treatment. But two years is typically the maximum length recovering addicts participate in studies so people who hold out longer aren't captured in the data. In one of the few large, long-term studies that looked at addiction to opiates like heroin found that 25 percent of users relapsed after 15 years.
Relapses are so common, Shrand said, because drug dependency is a chronic condition not unlike diabetes or heart disease. So, while an addict can be in recovery, their addiction can only be managed, never fully cured.
And in a circumstance like Hoffman's, where he had been off of drugs for years, Shrand said it's easy for people to let their guard down.
"They get it in their mind that they can go back to using just once or just a little. Or maybe they think that they can use another substance other than their substance of choice and be fine, but they can't," he said. "It just takes one moment of weakness to lead them down a path of destruction."
Heroin is especially habit-forming because it overrides the brain's pleasure receptors, explained Dr. Jason Jerry, a professor of medicine with the Cleveland Clinic's Alcohol and Drug Recovery Center.
"Heroin crosses the blood-brain barrier and is transformed chemically into morphine, a substance that gives the user a rush of euphoria," he said.
With each use, the brain craves another rush -- and another and another. Over time, the brain is completely rewired so that getting high becomes an obsession and a compulsion, he said.
Ceasing heroin use doesn't reverse changes to the brain, Jerry said. Once the circuitry is altered, the change is permanent. A brain primed for heroin always itches for the drug. This not only predisposes a user for a setback, it could also explain why slip-ups like Hoffman's are so often fatal.
After using on a regular basis, the drug loses its potency, Jerry said. Eventually an addict needs a greater quantity of substance to get the same high.
"When you wake up the monster that has been lingering dormant in the brain for years, cravings for the drug are as strong ever, but tolerance is much lower," Jerry explained.
Addicts often lose sight of this and start with a dose that is close to the amount they took when they were actively using, he said.
"The brain may be ready for it, but the body can no longer handle it," he said.
Jerry stressed that he didn't know if this is what happen in Hoffman's case, but that it was common for addicts coming out of a relapse to overdose in this way.
Details surrounding Hoffman's death are still emerging. By his own admission, the actor struggled with drug problems for years, beginning in his twenties.
Hoffman said he had kicked the habit for 23 years and had remained drug free until May 2013, when he briefly relapsed. He admitted to snorting heroin and checked himself into rehab.
Shrand said that no one should think of an addiction like Hoffman's as a moral issue.
"This didn't happen because he was weak," Shrand said. "This was an actual physical thing driven by the brain and his addiction didn't go away just because he didn't use for such a long time."