The scourge of marijuana looms large in Prime Minister Stephen Harper’s world, and in his campaign rhetoric. There are the ubiquitous Conservative Party’s “just not ready” attack ads that target Liberal Leader Justin Trudeau’s plan to legalize and regulate pot. And in the run-up to the election call, Health Canada spent $1.5 million in public funds to rerun its broadcast and Internet spots warning of the dangers of prescription drug and marijuana abuse. While Health Canada’s ads mesh perfectly with Conservative policy, they failed to get an endorsement from the Canadian Medical Association, which deemed the campaign “a political football on Canada’s marijuana policy.”

This week on the campaign trail, Prime Minister Stephen Harper was kicking around that pigskin with renewed enthusiasm, warning that legalizing pot would increase marijuana use, especially among youth, and would put Canadians at risk of long-term health damage. “When you go down that route, marijuana becomes more readily available to children, more people become addicted to it and health outcomes become worse,” Harper said.

Selling and taxing marijuana in stores as alcohol and tobacco are sold is “dangerously misguided,” he said. “Unlike the other parties, we will not introduce misguided and reckless policies that would downplay, condone or normalize the use of illegal drugs.” After successive governments have had success curbing tobacco use, why now open the door to marijuana? Harper asked.

Harper’s opposition is more than rhetorical. In his first six years as Prime Minister, police reported more than 405,000 arrests for simple pot possession, a 41 per cent increase. At the same time, the United States is climbing down from its hard line on marijuana use. Recreational marijuana use is now legal in the District of Columbia and four states: Washington, Colorado, Alaska and Oregon. Several other states have decriminalized possession, reducing it to a civil fine.

On Wednesday, the Toronto-based International Centre for Science in Drug Policy (ICSDP) entered the fray with a report that aims to use science-based findings to counter the emotion and rhetoric surrounding pot use. The global network of scientists and academics has a mandate to research and educate to “help guide effective and evidence-based policy responses to the many problems posed by illicit drugs.”

Its latest report, “Using Evidence to Talk about Cannabis,” looks at the science, or lack of science, behind common claims about marijuana use.

Although the report’s release was not timed to the early election call, it is meant to inform the debate at a time when many jurisdictions are rethinking their policies on marijuana prohibition, says M.J. Milloy, an assistant professor of medicine at the University of British Columbia and a member of the drug policy centre. “It’s funny; it’s almost like [Harper] read the report in advance and decided to repeat a lot of the most oft-discredited ideas,” Milloy said in an interview. “[Regarding] some of his most central concerns, the evidence that we have to date simply does not back them up.”

Here are some of the report’s findings, based on various research studies:

Claim: Marijuana is highly addictive.

“Scientific research has found that less than one in 10 people who use cannabis across their lifetime will progress to cannabis dependence, meaning that more than 90 per cent do not become addicted. The lifetime probability of becoming heroin-dependent, meanwhile, has been estimated at 23.1 per cent. Interestingly, the addictive potential of cannabis is also significantly lower than other illegal drugs, as 20.9 per cent of lifetime cocaine users, 22.7 per cent of lifetime alcohol users, and 67.5 per cent of lifetime nicotine users are estimated to become dependent . . . The negative consequences associated with cannabis dependence are far less than those associated with addiction to alcohol, cocaine, or heroin.”

Claim: “Marijuana is, on average, 300 to 400 per cent stronger than it was 30 years ago,” from a Health Canada television ad.

True, U.S. levels of THC in marijuana have increased about 300 per cent. “Concerns over increases in cannabis potency are rooted in the assumption that higher levels of THC are harmful to health. However, the harms of increased cannabis potency are not yet fully understood by scientists. Perhaps counterintuitively, some research suggests that higher cannabis potency may actually lead to a reduction in health harms (especially related to smoking), as consumers might reduce the volume they consume . . . A strict, legally regulated market for cannabis would put the regulation of THC levels in the hands of governments and public health officials, not criminal entrepreneurs.”

Claim: Legalization of pot will lead to an increase in availability and use.

“Evidence suggests that prohibition has been generally unsuccessful in reducing the availability of cannabis. In the United States, research indicates that, since 1990, the price of cannabis has decreased while potency has increased, despite increasing investments in enforcement.”

World Health Organization statistics show Canada has “the highest rates of teen use of marijuana of any industrialized country,” says Milloy. “This suggests to me that the current system isn’t working out. We’ve tried for 30 years the public security system, the arrest-the-dealer system, the demonize-the-user system and, in fact, what we’re seeing is more use, and more potent drugs [that are] easier to get.”

Claim: Regulation will not reduce drug crime.

“Cannabis regulation in Colorado, Washington State and Uruguay has diverted a substantial proportion (and likely the vast majority) of revenue from cannabis sales from the criminal market to illicit sellers, thereby decreasing the total share of the criminal market. Even a modest contraction in criminal opportunities and cartel profits can be viewed as a positive.”

Claim: Selling marijuana as tobacco or alcohol are sold is “dangerously misguided.”

The public health approach that has reduced tobacco use should be applied to marijuana, says Malloy. “It would mean the strict regulation, distribution and sale of marijuana—in other words, what we’re seeing in Washington State and Colorado and, increasingly, in other states—as a way of coming to grips with the use of marijuana, as a way of trying to reduce the harms that may come with drug use.”

The full report, and research citations, is available here.