AN INCREASING NUMBER of US adults are using marijuana, as fewer people perceive the drug as harmful, according to a survey of over 500,000 people.

The study analysed data from 596,500 adults who took part in the annual US National Survey on Drug Use and Health from 2002 to 2014.

Marijuana use (defined as having used marijuana in the previous year) increased from 10.4% in 2002 to 13.3% in 2014. The proportion of adults who first started using marijuana in the previous year increased from 0.7% in 2002 to 1.1% in 2014.

The prevalence of daily or near daily use (defined as people who use marijuana, on average, five days or more per week) increased from 1.9% to 3.5% over the same period.

Extrapolating the findings in line with the US population, the authors estimate that the number of adults who first used marijuana increased from 823,000 in 2002 to 1.4 million in 2014, and that the overall number of marijuana users increased from 21.9 million to 31.9 million.

They estimate that the number of daily or near daily users was 8.4 million in 2014, up from 3.9 million in 2002.

Perceived risk 

This increase is associated with a decrease in the proportion of people perceiving great risk of harm from smoking marijuana once or twice a week from 50.4% to 33.3%.

The research, published in The Lancet Psychiatry, notes that changes in marijuana use and perception of harm generally began in 2007.

The prevalence of marijuana use disorders – abuse or dependence – among adults in the general population remained stable at about 1.5% between 2002 and 2014, and the prevalence of marijuana use disorders among users declined (from 14.8% to 11%).

The authors suggest this may be because the large number of people who have started using marijuana in the past year might be using the drug less frequently.

While the study did not find an increase in the overall prevalence of marijuana use disorders among adults, it was not able to fully assess the impact of recent changes to state-level cannabis laws on widening use, and the authors say that continued monitoring of marijuana use and disorders at national and state-level is needed.

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Dr Wilson M Compton, one of the authors and a member of the National Institute on Drug Abuse, said: “Understanding patterns of marijuana use and dependence, and how these have changed over time, is essential for policy makers who continue to consider whether and how to modify laws related to marijuana and for health care practitioners who care for patients using marijuana.

Perceived risk of marijuana use is associated with high frequency of use suggesting the potential value for modifying risk perceptions of marijuana use in adults through effective education and prevention messages.

Compton noted that state laws related to marijuana use in the US have “changed considerably over the past 20 years”, with medical marijuana now legalised in 25 states and the District of Columbia. Several jurisdictions have also legalised non-medical marijuana use.

The research notes that people who used marijuana were more likely to develop dependence if they were male, younger, had low education, were not in full time employment, had depression and used tobacco or other substances.

The study did not include homeless people or prisoners, meaning that rates of drug use and drug use disorders could be even higher. The authors noted that the research did not look at other psychiatric disorders, such as psychosis or schizophrenia, so cannot provide information on the link between more severe psychiatric disorders and marijuana use.

Ireland 

There have been a number of calls for cannabis to be legalised in Ireland for medical reasons, with researching showing it could help alleviate certain symptoms suffered by people with illnesses such as Multiple Sclerosis and cancer.

Last month, a Bill on the issue was tabled in the Dáil by People Before Profit/Anti-Austerity Alliance.

In November 2015, the Oireachtas Justice Committee recommended that the possession of a small amount of illegal drugs be decriminalised – following months of research and public submissions.

The main findings of the committee’s report were:

• Drug possession could be dealt with by way of a civil response rather than the criminal justice system;
• Gardaí and health providers have discretion in choosing this option;
• Those found in possession would attend counselling and treatment meetings to help them stop using drugs;
• Research should be undertaken so that these measures are appropriate to Ireland.

Read: ‘Ireland is behind the times’: Should cannabis be legalised for medical use?

Read: Where do Ireland’s political parties stand on decriminalising cannabis?