Dr. Peter Martin, director of the Vanderbilt University Addiction Center in Nashville, said the 12 people selected for the study met the criteria for being "cannabis-dependent" -- they smoked pot an average 5.9 joints per day and did not want treatment to stop.
After exercising on a treadmill for 10 30-minute sessions during a two-week period, their craving and use of marijuana was cut by more than 50 percent, said Martin, the study co-author.
"This is 10 sessions but it actually went down after the first five -- the maximum reduction was already there within the first week," Martin said in a statement. "It shows that exercise can really change the way the brain works and the way the brain responds to the world around us and this is vital to health and has implications for all of medicine."
In 2009, about 16.7 million Americans age 12 or older reported using marijuana in the previous month and 6.1 million used the drug on 20 or more days per month, Martin said.