Governor Chris Christie recently spoke about treating substance abuse like the disease it is and the video went viral. He was spot on except at the very end when he said, “we need to start treating people in this country, not jailing them.”  It’s true we need to treat substance abuse, but the threat of jail is often what makes treatment work.

Crime in America is mostly a symptom of substance abuse. The Arrestee Drug Abuse Monitoring survey found that three-fourths of criminals tested positive for illegal drugs but only a fourth had ever had treatment. The CASA Columbia report Behind Bars says two thirds of prison inmates have diagnosable substance problems, and half of them are in prison for something they did when they were drunk or high.

As a psychiatrist, I’ve spent years working in jails, prisons, homeless clinics and drug treatment programs. My favorite question to ask my inmates patients is: “Have you ever been arrested for anything you did clean and sober?”

They usually stop and think for several seconds. I can see them counting off each incident. Then they smile and say, “No.” Prisons aren’t just filled with criminals; they’re filled with untreated substance abusers. If we could get them all into treatment and recovery, crime would drop dramatically.

But that’s where this story takes a twist. According to the National Survey on Drug Use and Health, nearly 90 percent of substance abusers don’t think they have a problem and don’t want treatment. When Amy Winehouse sang, “They tried to make me go to rehab; I said no, no, no” she spoke for addicts and alcoholics everywhere—including the ones in prison.

Most have no interest in treatment, and the ones who do want it often have so many other problems—head injuries, PTSD, severe child abuse—that they’d find it nearly impossible to stay in treatment on their own. So if we simply offer them treatment, most will fail. They’ll relapse back to drugs and alcohol, commit another crime, and end up back in prison. I’ve seen this revolving door a hundred times.

If we want them to get clean and sober and stay that way, we have to make them do it. There’s a misconception that people only get clean and sober when they’re ready to. Actually, no one is ever ready to. They get clean and sober when life gets so painful they have no choice. That’s why research shows that involuntary treatment works far better than so-called voluntary treatment. Research also shows that addicts are twice as likely to complete treatment when they’re explicitly told failure could mean going back to prison.

If we want addicted criminals to get into long-term recovery, we have to use some threat to keep them there, and the threat of going back to jail or prison is probably the best. I’ve seen lots of people get clean and sober because they were facing possible prison time. I’ve seen people coerced into drug court promising themselves they’d get high as soon as the year was over, but halfway through realized they liked being clean and sober. I’ve had patients tell me getting arrested was the best thing that ever happened to them because it got them out of their addiction.

So we should get rid of mandatory sentencing and give judges and probation and parole officers who actually know the criminals the flexibility to incarcerate when necessary and release when possible. But we shouldn’t get rid of the sentences themselves. Tough drug laws and the threat of jail save lives by keeping people in recovery.

Besides, nearly half of all prison inmates committed violent crimes, and drugs and alcohol are usually involved. This includes murderers, and I doubt Governor Christie wants to give them treatment instead of jail.

So while his speech was great, if he wants to keep the country safe while also making sure substance-abusing criminals stay in treatment, he shouldn’t call for treatment instead of jail. He should call for treatment as part of jail—and as part of prison and probation and parole. We need the threat of jail or prison. For many addicts and alcoholics, that threat might save their lives.

This appeared in Newsweek.