New York, Oct 22 (IANS): Marijuana use in the US more than doubled in the period from 2001-2002 to 2012-2013, says a study.

Researchers also found that the increase in disorders associated with marijuana use was almost as large for that period.

Nearly three out of 10 marijuana users experienced a marijuana use disorder of abuse or dependence in 2012-13, affecting some 6,846,000 people in the US, the research findings showed.

"At a time when Americans increasingly view marijuana use as harmless and favor its legalization, our findings suggest the need for caution and more public education about the potential for harm is warranted," said researcher Deborah Hasin, professor of clinical epidemiology at Columbia University Mailman School of Public Health in the US.

The researchers compared data from two US national surveys, one of 43,093 individuals conducted in 2001-2002, and the other of 36,309 individuals conducted in 2012-2013.

Very similar measures and procedures were used in the two surveys, allowing for comparisons.

Results showed that the prevalence of using marijuana in the previous 12 months was more than twice as high in 2012-2013 (9.5 percent) compared to 2001-2002 (4.1 percent), a significant increase.

Marijuana use disorders also increased substantially, from 1.5 percent of the adult population in 2001-2002 to 2.8 percent in 2012-2013.

The rise in marijuana use disorders was attributed to the increase in the prevalence of marijuana users.

The findings appeared online in the journal JAMA Psychiatry.