BEIJING, April 26 (Xinhuanet) -- U.S. government analysis of seized samples of marijuana and hashish show more of the cannabis on the market is stronger than in the past, which could account for a growing number of medical emergencies involving the drug, experts said Wednesday.

    Officials from the White House and National Institute for Drug Abuse cited data from the University of Mississippi's Marijuana Potency Project showing the average levels of THC, the active ingredient in marijuana, in the products rose from 7 percent in 2003 to 8.5 percent in 2006.

    The level had risen steadily from 3.5 percent in 1988.

    National Institute on Drug Abuse Director Dr. Nora Volkow fears the problem is not being taken seriously because many adults remember the marijuana of their youth as harmless.

    "It's really not the same type of marijuana," Volkow said in a telephone interview. "This could explain why there has been an increase in the number of medical emergencies involving marijuana."

    The pharmacy department at Mississippi has compiled data on 59,369 samples of cannabis, 1,225 hashish samples, and 443 hash oil samples confiscated since 1975. Hashish and hash oil concentrations are far higher, as they consist of processed plant product.

    "Researchers and treatment experts have argued for some time that today's more powerful marijuana has more harmful effects on users. This report underscores that we are no longer talking about the drug of the 1960s and 1970s -- this is Pot 2.0," John Walters, director of National Drug Control Policy, said in a statement.

    Volkow said demand has driven growers to cultivate the stronger stuff.

    "It is the market," she said. "Like in the market you favor the best tomatoes. When people buy marijuana, they don't want a weak cigarette."

    According to the National Survey on Drug Use and Health 4.1 million Americans, or 1.7 percent of the population, report they use marijuana.

    (Agencies)