A new U.S. government-funded report showing clear evidence cannabis is an effective remedy for those with chronic pain underscores the need for more research into how marijuana can help fight the deadly opioid crisis ravaging North America, according to one of Canada’s leading pain researchers. A report released by the National Academies of Sciences, Engineering and Medicine outlined nearly 100 conclusions about the benefits and harms of cannabis on a range of public health and safety issues.

Scientists at the University of York have shown that the risk of developing psychosis, such as hallucinations, from cannabis use is small compared to the number of total users. The research, published in the journal, Addiction, also showed for the first time that there is sufficient evidence to demonstrate that for patients who already have schizophrenia, cannabis makes their symptoms worse. In order to prevent just one case of psychosis, more than 20,000 people would have to stop using cannabis, as shown by a previous study led by the University of Bristol.

The use of cannabis medicines to treat people with depression, anxiety, psychosis or other mental health issues cannot be justified because there is little evidence that they work or are safe, according to a major new study. A review of evidence from trials conducted over nearly 40 years, published in the journal Lancet Psychiatry, concludes that the risks outweigh the benefits. And yet, say the authors, they are being given to people with mental health problems in Australia, the US and Canada, and demand is likely to grow. (See also: A big study on weed and mental health reveals just how little we know| Can we make cannabis safer?)

A new Canadian study about safe-injection sites for intravenous drug users concludes that they are cost-effective to the health-care system — an argument that is likely to be advanced as Montreal takes steps to open four such facilities in the city. Researchers at St. Michael’s Hospital in Toronto carried out an analysis that compared the projected costs of maintaining supervised injection sites over a period of 20 years with the potential savings to the health system in averted HIV and hepatitis C infections. The researchers’ estimates were conservative, as they did not include other infections associated with intravenous drug use and the costs involved in treating and hospitalizing patients suffering from overdoses.

CNN’s chief medical correspondent Sanjay Gupta wasn’t always on board with medical marijuana, but things changed when he looked for the science, he said during an interview on the Joe Rogan Experience. But to find the science that ultimately convinced him of the therapeutic potential of cannabis, he had to look internationally, because there seemed to be a “very biased set of data” in the U.S. that focused almost exclusively on the potential harms rather than benefits. “If you’re just looking at papers—well, this one [says there’s] potential long harm, this one possible addiction, this one gateway—you know, you’re seeing all those individual studies, but at a broader level, one step upstream, you realize that most of the studies that are getting funded are designed to look for harm,” Gupta said.

A 2012 Duke University study found that persistent, heavy marijuana use through adolescence and young adulthood was associated with declines in IQ. Other researchers have since criticized that study's methods. A follow-up study found that the original research failed to account for a number of confounding factors, such as cigarette and alcohol use, mental illness and socioeconomic status. Two new reports tackle the relationship between marijuana use and intelligence from two very different angles: One examines the life trajectories of 2,235 British teenagers between ages 8 and 16, and the other looks at the differences between American identical twin pairs in which one twin uses marijuana and the other does not.

For five years, a secret supervised drug injection site has operated in the US, allowing drug users to inject more than 10,000 times in a sterile, protected environment. The illegal operation is modeled after similar, legal sites in Canada and Europe, which seek to provide drug users with a place to get clean supplies, connect with social services and avoid overdosing in a dangerous place. A study of the underground site published in the New England Journal of Medicine online revealed how lives could be saved if the US were to sanction such facilities. An unnamed organization created the site in September 2014 in response to the opioid overdose crisis.

The team has revealed a brain mechanism specific to cocaine which triggers a massive increase in serotonin (the ‘happy’ hormone) in addition to the increase in dopamine (the neurotransmitter that causes addiction) common to all drugs. Serotonin acts as an intrinsic brake on the overexcitement of the reward system prompted by dopamine. The results are published in the latest edition of the prestigious journal Science. Contrary to popular thinking, cocaine only triggers an addiction in 20% of consumers, a statement issued by the university said. “The same principle applies to all potentially addictive products,” said Christian Lüscher, a professor in the Department of Basic Neurosciences at the UNIGE Faculty of Medicine, who led the research.

In research that turns on its head previous thinking about links between schizophrenia and smoking, scientists say cigarettes may be a causal factor in the development of psychosis. Previous studies have linked cannabis use to psychosis. But there is much debate about whether this is causal or whether there may be shared genes that predispose people to both cannabis use and schizophrenia. James MacCabe, a psychosis expert who co-led the research at King’s College London’s Institute of Psychiatry, said the new results suggest “it might even be possible that the real villain is tobacco, not cannabis” – since cannabis users often combine with tobacco.

The Mail on Sunday has shouted that "cannabis TRIPLES psychosis risk" and that skunk is to blame for "1 in 4 of all new serious mental disorders". Is this what the study shows? Well, no, they found that those with psychosis were much more likely to have used skunk every day, than to have never used cannabis. Conversely, people who smoked hash every day were no more likely to have psychosis than people who never tried cannabis. (See also: What media reports on the new cannabis study don't tell you | Why cannabis studies are needed | Skunk's psychosis link is only half the cannabis story)

If you believe budtender wisdom, consuming a strain called Bubba Kush should leave you ravenous and relaxed whereas dank Hippie Chicken should uplift you like a dreamy cup of coffee. But if you take pure, isolated delta-9-tetrahydrocannabinol, or THC—the main psychoactive ingredient in marijuana—you’ll experience “a high that has no specific character, so that seems boring,” says Mowgli Holmes, a geneticist and founder of a cannabis genetics company Phylos Bioscience. What gives cannabis “character,” in Holmes’s view, are the hundreds of other chemicals it contains. These include THC’s cousin cannabinoids such as cannabidiol, along with other compounds called terpenes and flavonoids.

In the evening after work, before closing time, a quick visit to the dispensary to buy one or two joints legally will soon become routine for around 400 cannabis lovers in Basel. For the first time in Switzerland, a broad-based study is being carried out in the canton of Basel-Stadt in order to investigate cannabis consumption behavior. The Federal Office of Public Health (FOPH) approved the first of several pilot studies with which various cities want to analyze the consequences of a legal sale of cannabis. Cities have been working toward these trials for years. The Basel project will initially last two and a half years, after which a balance sheet will be drawn up.

As more and more jurisdictions reconsider their cannabis policies, the public discourse is filled with conflicting evidence about the impacts of cannabis use and regulation. Cannabis causes schizophrenia. Cannabis is as addictive as heroin. Cannabis regulation leads to increased traffic fatalities. We hear claims like these all the time – but are they based on science? In our latest reports, the ICSDP investigates and provides comprehensive evaluations of the evidence for and against each claim.

Download the report (PDF) | Cannabis claims website

Legalizing marijuana in B.C. could generate $2.5 billion in government tax and licensing revenues over the next five years, according to a study published this month in the International Journal of Drug Policy. The information comes after Washington state and Colorado passed measures two weeks ago approving the legalization of marijuana for adult use under a strictly regulated system.

Research being conducted by a former Victoria city councillor is poking holes in marijuana’s reputation as a gateway drug. According to an academic paper authored by Philippe Lucas, marijuana may be an effective substitute for prescription drugs or alcohol, similar to the way methadone is used to treat heroin addicts. “The evidence suggests that cannabis is a potential exit drug for addiction,” Lucas said.

After Colorado legalized marijuana for recreational use this year, violent and property crime rates in the city are actually falling. According to data from the Denver Police Department, violent crime (including homicide, sexual assault, robbery, and aggravated assault) fell by 6.9% in the first quarter of 2014. Property crime (including burglary, larceny, auto theft, theft from motor vehicle and arson) dropped by 11.1%. A study looking at the legalization of medical marijuana nationwide, published in the journal PLOS ONE, found that the trend holds.

A new crime-data analysis has found that 241,000 people in Washington were arrested for misdemeanor marijuana possession over the last quarter-century, adding fuel to a campaign seeking to make this state the first to legalize recreational marijuana sales. The analysis estimates those arrests translated to nearly $306 million in police and court costs — $194 million of it the past decade. African Americans were arrested twice as often as whites for possession in Washington in the past 25 years, even though whites use marijuana more.

Marijuana-related emergency room visits in Colorado have increased at a higher rate for out-of-state guests than for residents since cannabis was legalized, according to a new study. The Northwestern Medicine and the University of Colorado School of Medicine looked at ER visits at more than 100 hospitals in Colorado in which there was a diagnosis of patients having used cannabis. Researchers compared the records from 2012, when the Colorado ballot measure passed to legalize marijuana, with 2014, when it was legally sold for recreational use. The study did not look at whether ER patients smoked marijuana or ingested edible marijuana products. Inexperienced users are unaware of the delayed effect of edibles.