The U.N. said more Americans are now seeking treatment for health problems related to cannabis use. The increase of cannabis-related health problems comes in spite of the worldwide decline in its consumption.

"In the United States, the lower perceived risk of cannabis use has led to an increase in its use," the United Nations Office on Drugs and Crime (UNODC) said. This recent report could intensify the debate on legalization of marijuana in the U.S. but the agency said it is still too early to relate the increase to the legalization of medical and recreational use of marijuana in several states including California and Colorado. It adds that the counted number of people seeking treatment comes from most regions in the world.

"Up to 200,000 people die every year due to illicit drugs," executive director Yury Fedotov of UNODC said. According to the report, U.S. cannabis-related cases in the emergency department increased 56 percent from 2006 to 2010 while admission to treatment centers for drug abuse increased 14 percent over the same study period.

While marijuana use shows a decline in several European countries, the U.N. said that the United States' perception of lower risk of cannabis use resulted to an increase in consumption. More young people trying out the drug and increased availability may also result to a rise in consumption. The U.N. noted that illegal opium poppy farming increased 26 percent from 2012 to 2013 worldwide.

Colorado allowed the sale of marijuana at stores for consumers aged 21 years old and above since early 2014. The first cannabis stores will soon open doors in Washington where officials said their goal is to keep marijuana away from people under the age of 21.

In 2013, Uruguay legalized the farming, sale and use of marijuana as a first social experiment that aims to wrest control of the cannabis crop from criminals. The whole world including the United States continue to watch the experiment closely amid debates regarding the legalization of the drug.

Critics said marijuana legalization will increase consumption and begin the prospect of use and legalization of harder drugs such as heroin. With the war on drugs facing public criticism for failing to dissuade the illegal business, Uruguay's success may be the only fuel to legalization in other parts of the world.