Laws that succeeded in curbing homegrown methamphetamine labs also opened the door to imports of highly pure "ice," in turn triggering a rise in meth addiction and treatment admissions, researchers say.

MedPage Today reported May 24 that researchers at the American Psychiatric Association meeting in Toronto said that treatment admissions for meth have risen from 28,000 in 1993 to 150,000 in 2004. Current data indicates, however, that meth use has remained fairly constant, with lifetime use at about 5.1 percent of the population and past-month use at 0.3 percent.

National Institute on Drug Abuse researcher James Colliver, Ph.D., said that more addicts are smoking the purer "ice" version of meth rather than injecting or inhaling diluted powder forms of the drug: 80,000 of the 150,000 people admitted to treatment for meth addiction in 2003 said they smoked the drug.

"Smoking is a route of administration that delivers the drug very rapidly to the brain, producing greater reinforcement effects, which therefore may produce higher rates of dependence," Colliver said.

The purer form of the drug also is more likely to cause brain damage, researchers said.