Many methamphetamine users who joined a residential rehabilitation program to quit their drug use succeeded initially - but after three years, all but a few had gone back to using, according to a new study from Australia.

Shorter detoxification treatments had even less impact on getting meth users clean, researchers found.

Richard Rawson of the University of California, Los Angeles Integrated Substance Abuse Programs said the problem with many treatment programs is they end too soon.

"Addiction is much more of a chronic disorder," said Rawson, who was not involved in this study. "Once you've changed your brain from using drugs like methamphetamine, there's going to be a propensity to relapse."

According to the National Institute on Drug Abuse, 314,000 teens and adults in the United States were current meth users in 2008. Meth use and treatment increased in the 1990's and early 2000's, but may now be on the decline.

There are few addiction treatment programs tailored to methamphetamine users, and instead people often go through programs designed with heroin or alcohol in mind, said Rebecca McKetin, the lead author of the new study from the Australian National University in Canberra.

"Their utility for methamphetamine users is not well understood," she wrote in an email to Reuters Health.

For the new study, McKetin and her colleagues, who published their findings in the journal Addiction, compared long-term meth use in 248 people treated in a rehab program and 112 in a detox program with 101 meth users who weren't undergoing treatment at the time.

Residential rehab typically entails several months of living at a drug-free center that offers individual or group counseling and social and recreational activities, such as gardening or cooking. Detox, on the other hand, often involves just a few days at a hospital or other medical facility.

After three months, interviews with people in the study showed those who went through detox were just as likely to still be using meth as those in the no-treatment comparison group.

Rawson said this is not surprising.

"There really is no benefit from detox alone. You're not really providing treatment, you're simply providing a medical intervention that can help people reduce their symptoms," he said.

Users who went through rehab, however, were much less likely to continue doing meth after three months.

The researchers estimated that rehab resulted in 48 percent of people remaining abstinent from the drug, compared to 15 percent in the other groups.

Over time, that success faded.

At one year, 20 percent of users who went through rehab had given up the drug, compared to seven percent of people in the detox and no-treatment groups combined.

And by three years, just 12 percent of users who entered rehab remained clean, compared to five percent of those who didn't go into rehab.

Is rehab worth it?

"On the one hand, many people were disappointed with the outcomes for residential treatment, because there is an expectation that these types of long-stay residential treatments produce long-term recovery, and we found that this was not the case for most people," McKetin wrote.

"On the other hand, the large reductions in drug use seen in the short-term were excellent," she added.

Rawson said for drug addiction treatments to be sustainable, they have to continue over a longer time - but it's unclear whether that means months or years.

"Some people really have trouble grasping the fact that they need help for a longer period of time. They want to go into rehab, get fixed, and go on with their life," he said.

Other drug treatment methods aside from rehab and detox include outpatient individual or group counseling.

McKetin said it's not clear whether residential rehabilitation is a good investment in terms of costs and benefits.

According to her study, a rehab stint can cost about $11,000.

"It may not be perfect, but in the absence of better (treatments), we need to offer people some respite from their addiction in times of crisis," she said.