WASHINGTON (Reuters) - The marijuana being sold across the United States is stronger than ever, which could explain a growing number of medical emergencies that involve the drug, government drug experts on Wednesday.

A man smokes marijuana duringa music festival in Indio, California, April 30, 2006. The marijuana being sold across the United States is stronger than ever, which could explain a growing number of medical emergencies that involve the drug, government drug experts on Wednesday. REUTERS/Lucas Jackson

Analysis of seized samples of marijuana and hashish showed that more of the cannabis on the market is of the strongest grade, the White House and National Institute for Drug Abuse said.

They 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. “The highest concentration of (THC) found in a cannabis (marijuana) sample is 33.12 percent from Oregon State Police,” the report reads.

‘THIS IS POT 2.0’

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.”

Volkow’s institute has been studying the effects of cannabis, whose active ingredients are very similar to important brain chemicals called endogenous cannabinoids.

“It clearly is addictive,” she said.

If children and adolescents use marijuana, it could affect their still-developing brains, she said.

The report said more than 60 percent of teens receiving treatment for drug abuse or dependence report marijuana as their primary drug of abuse.

“Although the overall number of young people using marijuana has declined in recent years, there is still reason for great concern, particularly since roughly 60 percent of first-time marijuana users are under 18 years old,” Volkow said.

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.