The United Nations Office on Drugs and Crime says global markets for heroin, cocaine and cannabis declined or remained stable last year, but the production and abuse of prescription and synthetic drugs increased.

In its annual World Drug Report issued Thursday, the U.N. agency says global production of heroin's key ingredient, opium, dropped 38 percent in 2010 from a year earlier, largely due to a plant disease that wiped out much of the opium poppy harvest in Afghanistan. Despite the ruined harvest, the report says Afghanistan remained by far the world's largest opium producer, accounting for 74 percent of the global total, or 3,600 tons.

UNODC says the decline in global opium output may be temporary because Burma is re-emerging as a major producer, with its share of global production rising to 12 percent last year from five percent in 2007. It says Burmese land used for opium cultivation grew 20 percent in 2010 from a year earlier, driving the increase in production.

The U.N. agency says global cultivation of the coca plant used to make cocaine dropped 18 percent from 2007 to 2010, due largely to reduced coca growing in Colombia, a major supplier. It reports “massive declines” in U.S. cocaine demand in recent years, but says the United States remains the world's largest market for the illicit drug, consuming 157 tons in 2009.

UNODC says cocaine consumption in Europe is catching up to the United States, with consumption doubling over a decade to 123 tons in 2009.

The report says the extent of the global cannabis problem did not change significantly in 2009. It says cannabis remained the world's most widely produced and consumed illicit substance, with an estimated 125 million to 203 million people aged 15 to 64 using it at least once a year.

With many nations fighting drug production and trafficking, UNODC says drug users increasingly are abusing legally-available substitutes for illicit stimulants, particularly in Southeast Asia. It says global seizures of amphetamine-type stimulants, or ATS drugs, hit a record high in 2009.

The U.N. report says the total number of people around the world who used illicit drugs at least once a year is estimated at 210 million, almost five percent of the world's population.

The White House said Thursday confronting the global drug problem, including a prescription drug abuse “epidemic,” is a “shared responsibility that requires a sustained and comprehensive approach” beyond the use of law enforcement. It says the United States is making efforts to emphasize drug prevention and expand access to treatment in cooperation with international partners.