As U.S. law loosens up on marijuana, more people start to see marijuana as a less of a health risk, according to the United Nations' drug agency. According to their report, more people worldwide, including in North America, have sought out treatment for cannabis abuse.

"We have an increase in harmful use of cannabis in the United States," said Angela Me, a chief researcher of the U.N. Office on Drugs and Crime (UNODC).

In their report, the UNODC said that it's too soon to fully understand the impact of legalization in Washington, Colorado, and the nation of Uruguay. But they did cite research that "more permissive cannabis regulations correlate with decreases in the perceived risk of use" could affect greater consumption rate in young people. The increased availability could also lead to wider use and abuse, the UNODC said.

"Medical research tell us clearly that the use of cannabis, particularly at early ages, can be very harmful for the health," Me said.

On the other hand, overall global cannabis use has decreased, especially in European countries, but the report did not answer what caused this change.