United States: Adult cannabis use has doubled in 10 years

The number of adults who have used cannabis has more than doubled over the past 10 years, according to a report combining data from two major studies.

In 2001, only 4.1% of adults said they had used marijuana. This figure rose to 9.5% in 2013. The results were published Wednesday in the journal JAMA Psychiatry.

The researchers also found that’cannabis abuse and dependence have increased over the past 12 years, This is probably because the total number of adults using marijuana has also risen enormously.

This increase in marijuana use comes at a time when Americans' attitudes towards cannabis legalization have evolved. Less than a third of Americans were in favor of legalizing marijuana in 2002, while a majority now support legalization, according to a study by the Pew Research Center.

Since 2012, US states have been legalizing small amounts of cannabis for recreational use. Cannabis is now legal in 4 states, plus the District of Columbia. And medical cannabis is legal in 23 states.

The study draws no other conclusions. «We've only shown that it happened,» says Deborah Hasin, the study's lead author. «Now the thing that needs to be studied is: why. We can speculate that Americans increasingly see marijuana as a harmless substance, or the laws have changed. But we won't know until we do empirical studies on what factors have influenced this increase.»

The study also sought to identify any cases of dependence or abuse. According to the study results, use disorders among consumers fell slightly. Almost 3 out of 10 cannabis users have experienced dependence or abuse, which still represents 6.8 million Americans if the survey is extended to the entire U.S. population.

Deborah Hasin says it's important to present information in a «balanced way», especially when talking about the risks associated with cannabis use.

«While a lot in the U.S. believe that prohibition of recreational cannabis should end, this and other studies suggest caution and a need for public education about the potential dangers of cannabis use, including the risk of addiction. As with alcohol, some individuals can consume cannabis without becoming addicted. However, the proven risk of having a bad experience with cannabis among current users suggests that as the number of users grows, so will the number of people experiencing such problems in connection with their consumption.».