"Just as the case for alcohol, not everybody who uses it is harmed but there are some risks", Hasin told Reuters Health.
In other words, the rates of illegal marijuana use increased more quickly in states with medical marijuana laws, the researchers said.
"The laws may not be too relevant and salient to teenagers so we thought it was important to look at adults", said Hasin. The 2011 study suggests more research. The study concluded that "the most likely of several possible explanations for higher adolescent marijuana use and lower perceptions of risk in MML (medical marijuana law) states can not be determined". In the DSM IV, cannabis abuse and dependence were separate disorders and neither withdrawal nor craving were criteria for a dependence diagnosis.
Between the first and third surveys, the researchers found that illegal marijuana use increased more in the states that passed the laws compared to those that didn't. In the states that never passed medical marijuana laws, the rates of illegal use of the drug rose from 4.5 percent to 6.7 percent - an increase of 2.2 percentage points.
The pattern was similar for drug use disorder.
States with medical marijuana laws also saw an increase in people who can't stop using pot even though it's interfering with many aspects of their lives, researchers said.
They used data from national surveys of drug use among adults (ages ≥18) conducted at three time points: before the enactment of medical marijuana laws (1991-1992); just after the laws were enacted in a few states (2001-2002); and after wide enactment of the laws (2012-2013), when more than one-third of people in the USA lived in states with MMLs.More news: Venezuela threatens to exit OAS as pressure on Maduro mounts
The current Nevada law allows adults over the age of 21 to possess up to 1 ounce of marijuana and consume it in the privacy of their homes. The state will license a limited number of growers, product manufacturers and dispensaries to sell marijuana to patients starting next year.
"I think all of these things can contribute to increases, but we can't pinpoint them for sure because it's not what the study was created to address", said Hassin. However, changing state laws - medical or recreational - may also have adverse public health consequences, including cannabis use disorders.
Laws and attitudes regarding cannabis have changed over the last 20 years.
The biggest increases in illicit marijuana use were seen between 2001-2002 and 2012-2013. If Congress fails to pass a spending bill, Attorney General Jeff Sessions could follow the NDAA's Marijuana Policy Perspective and begin enforcing federal marijuana laws as soon as April 29, 2017.
For example, she said, research has tied medical marijuana laws to fewer opioid overdose deaths.
In particular, the biannual poll conducted by the Colorado Department of Public Health and Environment showed that teen marijuana use fell dramatically in Colorado after the state opened its recreational marijuana market.
Dr. Wilson Compton, the deputy director of the National Institute on Drug Abuse, said the recent research was a "strong design to test the implications" of the new marijuana laws.