By STEVE MITCHELL
Senior Medical Correspondent
WASHINGTON, Oct. 13 (UPI) -- Scientists said Thursday that marijuana appears to promote the development of new brain cells in rats and have anti-anxiety and anti-depressant effects, a finding that could have an impact on the national debate over medical uses of the drug.
Other illegal and legal drugs, including opiates, alcohol, nicotine and cocaine, have been shown to suppress the formation of new brain cells when used chronically, but marijuana's effect on that process was uncertain.
Now, a team led by Xia Zhang of the department of psychiatry at the University of Saskatchewan in Saskatoon may have found evidence the drug spurs new brain cells to form in a region of the brain called the hippocampus, and this in turn reduces anxiety and depression.
Marijuana appears "to be the only illicit drug whose capacity to produce increased ... neurons is positively correlated with its (anti-anxiety) and anti-depressant-like effects," Zhang and colleagues wrote in the November issue of the Journal of Clinical Investigation. The paper was posted online Thursday.
In the study, rats were given injections of HU210 -- a synthesized version of a cannabinoid chemical found in marijuana -- twice per day for 10 days.
Zhang told United Press International this would be "a high dose" of smoked marijuana, but he added he is not certain how many equivalent joints it would take or whether patients now using the drug typically would be getting this much HU210.
Although HU210 was injected, Zhang said there would be no difference if it was obtained by smoking marijuana.
The rats showed evidence of new neurons in the hippocampus dentate gyrus, a region of the brain that plays a role in developing memories.
Zhang's team suspected the new brain cells also might be associated with a reduction in anxiety and depression, because previous studies had indicated medications used to treat anxiety and depression achieve their effect this way.
To find out, they treated rats with HU210 for 10 days and then tested them one month later. When placed in a new environment, the rats were quicker to eat their food than rats that did not receive the compound, which suggested there was a reduction in anxiety behaviors.
Another group of rats treated with HU210 showed a reduction in the duration of immobility in a forced swimming test, which is an indication the compound had an anti-depressant effect.
Asked how he thought the findings might impact the debate over using marijuana to treat medical conditions, Zhang said, "Our results indicate cannabinoids could be used for the treatment of anxiety and depression."
He added that his view is "marijuana should be used as alcohol or nicotine," noting "it has been used for treating various diseases for years in other countries."
Last June the U.S. Supreme Court voted 6-3 that the federal ban on marijuana supersedes the laws of certain states that allow the substance to be used for medicinal purposes, such as the treatment of pain, nausea in cancer patients and glaucoma. Eleven states have passed laws legalizing marijuana use by patients with a doctor's approval, including California, Alaska, Colorado, Hawaii, Maine, Montana, Nevada, Oregon, Vermont and Washington.
The Bush administration, through the Department of Justice's Drug Enforcement Agency, began conducting raids in California in 2001 on patients using marijuana. Two of those arrested by the DEA -- Angel Raich, who suffers from brain cancer, and Diane Monson, who used the drug to help alleviate chronic back pain -- sued Attorney General John Ashcroft, requesting a court order to be allowed to grow and smoke marijuana, which led to the Supreme Court decision.
Paul Armentano, senior policy analyst with the National Organization for the Reform of Marijuana Laws, told UPI he thought the findings "would have a positive impact on moving forward this debate, because it is giving ... a scientific explanation that further supports long-observed anecdotal evidence, and further lends itself to the notion that marijuana, unlike so many other prescription drugs and controlled substances, appears to have incredibly low toxicity and as a result lacks potential harm to the brain that many of these drugs have."
The DEA Web site, however, contends that "marijuana is a dangerous, addictive drug that poses significant health threats to users," including cancer and impaired mental functioning.
Armentano said this is a distortion of what scientific studies actually show. Studies in animals indicate marijuana actually may protect against many forms of cancer, rather than cause the disease, he said. In addition, studies in marijuana smokers have found little evidence of cognitive deficits, and even when they do, the defects disappear if the person stops smoking for 30 days.