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Photographer: Junaidi Hanafiah /Anadolu Agency/Getty Images Photographer: Junaidi Hanafiah /Anadolu Agency/Getty Images

Thanks to innovation, illegal marijuana users are getting a stronger—and possibly more harmful—high today than they did 10 years ago.

The potency of cannabis, commonly measured by concentration of tetrahydrocannabinol, or THC, has steadily increased over the past decade in the U.S. and Europe, the two major marijuana markets, according to the annual World Drugs Report by the United Nations Office on Drugs & Crime.

High THC intake has been associated with anxiety, depression, and psychotic symptoms in users, and it affects the lungs and the heart. The conditions more frequently occur among regular users, although anxiety or psychotic symptoms may also occur in recent and inexperienced users, the UNODC said.

The rise in THC content is driven by "rapid advancement in cannabis plant cultivation techniques,'' such as selective breeding and improved harvests in both yield and potency, according to the report.

Europe, the largest market, reported an average cannabis potency of more than 10 percent in 2012, with most European countries seeing an increase in THC content since 2006. There has also been a rise in cannabis-related health problems during those same years, in which the number of individuals seeking help for cannabis use rose from 45,000 to 59,000. Nearly half of them were daily users.

In the U.S., THC levels increased from less than 3.4 percent in 1993 to 8.8 percent in 2008, the UNODC said. More recent federal data from the U.S. of seized illegal cannabis shows that the THC content of marijuana has increased in the past two decades from 3.7 percent in 1993 to 12.6 percent in 2013.

Chart: United Nations Office on Drugs and Crime

As more U.S. states start legalizing marijuana, cannabis use among Americans above the age of 12 increased in 2013 to 25.8 percent of that demographic, from 24.7 percent in 2012.

Chart: United Nations Office on Drugs and Crime

While one recent survey showed that weed prices in Colorado, one of the four U.S. states that legalized medical and retail marijuana, are falling faster than expected, that didn't seem to have affected last year's profits. Monthly tax revenue last year ended at $8.5 million in December, nearly triple that earned in January, according to the Colorado Department of Revenue. Total monthly revenue, including licenses and fees, is poised to net approximately $76 million for the 2014 calendar year, according to the report.

Chart: United Nations Office on Drugs and Crime

The horizon isn't as green for cocaine. Coke supply is now at its lowest level since estimates from the mid-1980s, and demand is shrinking as well.

Chart: United Nations Office on Drugs and Crime

As authorities intensify efforts to eradicate coca bush fields and dismantle cocaine-producing laboratories, global coca bush cultivation fell 10 percent in 2013 from a year earlier. The fall is driven mainly by cuts in the three main cocaine providers—an 18 percent decrease in Peru and a 9 percent cut in Bolivia. Potential production of pure cocaine in Colombia is estimated at 290 tons, the lowest level since 1996.

Chart: United Nations Office on Drugs and Crime

Cocaine markets are shrinking the most in the U.S. and, most recently, in Canada. Cocaine use among high school students has nearly halved since 2006, and the proportion of young people who feel that cocaine is easy to obtain has also declined in recent years, according to the UN report:

"Supply reduction measures may have led to a reduction in the size of the cocaine market in some areas of the world, reflected in the number of seizures made and in the decline in the prevalence of cocaine use."

Chart: United Nations Office on Drugs and Crime

For more, read this next: These Three Maps Show How Drugs Move Around the World