In the United States, laws and attitudes toward the use of marijuana are changing. Twenty-three states now have medical marijuana laws, and marijuana use is higher in states with such laws than in other states. Four of these states have also legalized marijuana for recreational use. More Americans now favor legalization of marijuana use than in previous years. Further, fewer Americans view marijuana use as risky, although studies have shown that use or early use of marijuana is associated with increased risk for many outcomes, including cognitive decline, psychosocial impairments, vehicle crashes, emergency department visits, psychiatric symptoms, poor quality of life, use of other drugs, a cannabis-withdrawal syndrome, and addiction risk. Further, marijuana use disorders (abuse or dependence) are associated with substantial comorbidity and disability and are consequently of substantial public health concern.

So begins a new paper looking at an old question: how does drug legalization affect use and misuse?

This week’s Reading: “Prevalence of Marijuana Use Disorders in the United States Between 2001-2002 and 2012-2013” by Deborah S. Hasin et al., just published online (and ahead of print) by JAMA Psychiatry.

You can find the paper here:

Columbia University’s Hasin and her co-authors have picked a timely topic. Here’s a quick summary: as laws and public attitude have shifted, looking at U.S. survey data, they conclude that marijuana use has sharply increased.

Deborah S. Hasin

As noted in the opening paragraph, there is a major legal change in the United States: legalization of marijuana for medical use has occurred in 23 states, and for recreational use, in four. And there has been a major cultural change. It seems like only yesterday that our American neighbours were shocked by presidential candidate Bill Clinton’s admission that he had once used pot (though, for the record, he claimed not to have inhaled); today, Americans have a more liberal attitude.

Bill Clinton: Didn’t inhale

This is an American paper drawing on American data, but it’s very relevant on this side of the 49th parallel. After all, marijuana is now available here for medical use. And the Prime Minister-designate suggests that he favours legalization. Speaking of cultural shift, I no longer ask my patients about “street drug” use and assume that the term covers marijuana – people today don’t put THC in the same category as, say, cocaine.

Are Americans using more marijuana? Is abuse and dependence up? The study authors seek to answer these questions.

Here’s what they did:

· The authors compared results from two surveys.

· 2012-2013 NESARC-III is “a nationally representative face-to-face interview survey of 36,309 adults aged 18 years and older residing in households and selected group quarters, with respondents selected through multistage probability sampling.” The overall response rate was 60.1%

· The 2001-2002 NESARC was “a nationally representative face-to-face interview survey of US adults” with similar sampling to the NESARC-III, and involving 43,093 people. The response rate was 81.0%.

· In both surveys, marijuana use disorder was gauged with structured interviews (the National Institute on Alcohol Abuse and Alcoholism Alcohol Use Disorder and Associated Disabilities Interview Schedule–5, AUDADIS-5, or a variant).

· Statistical analysis was done with several tools, including pairwise t tests and SUDAAN 11.0.1.

Here’s what they found:

· Past-year marijuana use was significantly up: 4.1% in 2001-2002 and 9.5% in 2012-2013. (!!) Significant increases were found among many groups: “among women (2.6% vs 6.9%), black individuals (4.7% vs 12.7%), Hispanic individuals (3.3% vs 8.4%), those in the South (2.9% vs 7.7%), and middle-aged (1.6% vs 5.9%) and older (0.04% vs 1.3%) adults.” See below.

· The prevalence of DSM-IV marijuana use disorder increased significantly between 2001-2002 (1.5%) and 2012-2013, from 1.5% to 2.9% – a near doubling. (!!)

· The prevalence of past-year DSM-IV marijuana use disorder among users was 35.6% in 2001-2002 and 30.6% in 2012-2013, and decreases were noted among many groups, but statistically significant in only some: “white individuals, black individuals, those never married, those in the mid-income range, those in urban areas, and those in the Northeast and Midwest.”

The authors note:

In 2012-2013, 9.52% of US adults used marijuana in the past year, and 2.9% had a diagnosis of DSM-IV marijuana use disorder. Thus, nearly 3 of every 10 marijuana users had a diagnosis of a marijuana use disorder (approximately 6 846 000 Americans). Further, since 2001-2002, the prevalence of adult past-year marijuana use and past-year marijuana use disorders increased markedly; the prevalence of past-year marijuana use more than doubled, while the increase was nearly 2-fold in the prevalence of past-year marijuana use disorder.

They conclude:

In summary, while many in the United States think prohibition of recreational marijuana should be ended, this study and others suggest caution and the need for public education about the potential harms in marijuana use, including the risk for addiction. As is the case with alcohol, many individuals can use marijuana without becoming addicted. However, the clear risk for marijuana use disorders among users (approximately 30%) suggests that as the number of US users grows, so will the number of those experiencing problems related to such use. This information is important to convey in a balanced manner to health care professionals, policy makers, and the public.

1. This paper isn’t incredibly sophisticated – essentially, it compares survey data from two different time periods – but draws on an awesomely large dataset. No surprise then that it has gained much attention, even gaining a mention in USA Today.

2. The authors clearly see public-policy implications. That said, while marijuana is much discussed in Canada and the United States, little of this discussion seems guided by doctors and public health experts. This paper suggests that this approach is deeply problematic.

3. Regardless of our personal beliefs about drug legislation, NIMH’s David Goldman’s accompanying commentary notes the need for more research and thoughtfully calls for action. He writes: “People using cannabis often and in potent forms are more likely to experience negative consequences. Yet, data on the effects of heavy exposures are lacking, even as access to potent cannabis is becoming easier. The burden of cannabis’ effects may fall more heavily on people who, because of genetic makeup or early life exposures, are at greatest risk for brain structural changes, psychosis, or addiction.” To bring this back to a Canadian context: if Prime Minister-designate Trudeau favours marijuana legislation, should he also favour marijuana research?

Further Reading

This paper touches on a larger debate on legalization. I draw attention to two good essays on the topic.

In Maclean’s, Ken McQueen makes the case for legalization.

In Commentary, David Frum makes the case against it.

Reading of the Week. Every week I pick a reading — often an article or a paper — from the world of Psychiatry.