(USA TODAY) -- Half of the men arrested in 10 U.S. cities test positive for some type of illegal drug, a federal study found.

Not only do the findings show "a clear link between drugs and crime," they also highlight the need to provide drug treatment, says Gil Kerlikowske, director of the White House Office of National Drug Control Policy, which will make the data public today.

Assessing offenders for drug and mental health problems and providing treatment is "important if you want to stop recidivism and recycling people through the system," says Kerlikowske, who supports drug courts that offer court-ordered drug treatment.

"There's an opportunity when someone is arrested to divert them to treatment if they need it," says Bill Piper, director of national affairs for the Drug Policy Alliance Network, a group that supports legalizing marijuana and treating drug use as a public health issue. "But people shouldn't have to get arrested to get treatment."

In 2008, researchers interviewed and obtained urine samples from 3,924 men arrested in 10 metropolitan areas: Atlanta, Charlotte, Chicago, Denver, Indianapolis, Minneapolis, New York, Portland, Ore.; Sacramento and Washington, D.C.

In Chicago, 87% tested positive for drug use, and in Sacramento, 78% tested positive. Many of the men -- 40% in Chicago and 29% in Sacramento -- tested positive for more than one drug.

Marijuana was the most common drug in every city where testing was done except Atlanta, where cocaine was most prevalent, the study found. Methamphetamine use was concentrated on the West Coast where 35% of the men arrested in Sacramento and 15% of the men arrested in Portland tested positive for the drug.

Heroin use was highest, at 29%, among men arrested in Chicago, an increase from 20% in 2007. Heroin use among arrestees declined in Portland, from 12% in 2007 to 8% in 2008.

Positive drug tests declined since 2007 among men arrested in Atlanta, Portland and Washington, the study found. Some of that decline can be attributed to law changes, Kerlikowske says.

Portland passed laws restricting access to ingredients needed to make methamphetamine, Kerlikowske says.

Cities and states need more resources for drug treatment, says Marc Mauer, executive director of the Sentencing Project, which advocates alternatives to incarceration.

"If you just want drug treatment, in some places you are better off getting arrested and going to drug court," Mauer says.

"The federal resources that have gone into the drug war have been heavily oriented toward police and incarceration rather than treatment. We need to shift that use of resources," he says.

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