Many young adults remember their childhood participation in Drug Abuse Resistance Education, better known by the acronym D.A.R.E. One of the program's core messages is that marijuana is a "gateway" to all sorts of other substances. D.A.R.E's effectiveness was later called into question, and its curriculum overhauled, but the legend remains. The scientist who coined the "gateway" termrecently came out with a new paper showing that it's actually nicotine that is, biologically, the most potent of gateway of all.

Cannabis is associated with psychosis (a symptom) and schizophrenia (an illness where this symptom is persistent) in complex, contradictory and mysterious ways. The evidence does demonstrate various links that we all should all be aware of, especially cannabis users and parents. However, the evidence does not support anything like the level of fear propagated in the media.

Scientists and politicians still debate whether using “soft” drugs necessarily leads a person down a slippery slope to the harder stuff. Critics note that marijuana has, in some cases, been shown to actually prevent people from abusing other substances. But new research is breathing fresh life into the perennially controversial theory, and the timing seems apt. As marijuana legalization and the opioid epidemic sweep across the country, parents are once again questioning the root causes of addiction. And politicians opposed to legalization, including Attorney General Jeff Sessions and Gov. Chris Christie of New Jersey, have routinely used the gateway effect as their chief argument against reform.

A major meta-analysis published earlier this year that questioned the empirical evidence for supervised drug consumption sites has been retracted by the International Journal of Drug Policy. But the meta-analysis, which I reported on shortly after it published, concluded that supervised consumption sites have a small favorable relation to drug-related crimes, but no significant effect on several other outcomes, like overdose mortality and syringe sharing. In short, the meta-analysis didn’t conclude that supervised consumption sites were bad, but they didn’t appear to do much on key outcomes like overdose death. But the meta-analysis apparently had serious methodological flaws in how it evaluated outcomes.

That cannabis and schizophrenia are linked is widely accepted. Several studies suggest the drug can set off short-term psychotic episodes in those already suffering from the condition. Other research, though, does more than this. It shows that people with schizophrenia are twice as likely as others to use cannabis. This leads some to argue that the drug is actually a cause of schizophrenia rather than just a trigger—a line of evidence sometimes employed by those who wish to keep it illegal.

As one public health emergency sees policymakers around the world turn to the best available science to stem its tide, another deadly crisis rages on while science remains noticeably absent. In Canada and many other countries, the rapid scaling up of evidence-based responses to the outbreak of coronavirus has seen politicians standing alongside public health officials to deliver the latest updates on how governments are responding to limit the spread of the virus and minimize its harms. Contrast that to the ongoing opioid overdose crisis, where it seems politicians are too often seen standing next to the critics of those same public health officials. This is a concerning reality given that approximately 12 Canadians die every day of an opioid overdose.

For over two decades, cannabis, commonly known as marijuana, has been the most widely used illicit drug by young people in high-income countries, and has recently become popular on a global scale. Epidemiological research during the past 10 years suggests that regular use of cannabis during adolescence and into adulthood can have adverse effects. Epidemiological, clinical, and laboratory studies have established an association between cannabis use and adverse outcomes.

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More than 2,700 years ago, worshipers at a "holy of holies" shrine in Israel may have gotten high on weed. Researchers discovered burnt cannabis and frankincense at the site, which was located in the Kingdom of Judah. Researchers made the discovery after analyzing ancient residues left on two altars at the shrine. The burnt cannabis is "the first known evidence of [a] hallucinogenic substance found in the Kingdom of Judah," a region that now includes parts of the West Bank and central Israel, the researchers wrote in the study. The cannabis finding indicates that people may have purposefully used the plant for its "hallucinogenic ingredients," to stimulate ecstasy during cultic ceremonies.

A recent systematic review concluded that cannabis use increases risk of psychotic outcomes independently of confounding and transient intoxication effects. Furthermore, a model of the association between cannabis use and schizophrenia indicated that the incidence and prevalence of schizophrenia would increase from 1990 onwards.

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Brain scans have revealed for the first time how a substance found in cannabis plants may help people with psychotic disorders by dampening down abnormal brain activity that arises in the patients. A single dose of cannabidiol, an non-intoxicating extract of the plant, reduced unusual patterns of neural behaviour linked to hallucinations, delusions, and other symptoms of psychosis, researchers found. The impact of the substance has raised hopes that medical preparations of pure cannabidiol, or new drugs based on the compound, may be turned into effective treatments for young people who develop psychosis but do not respond to existing therapies.

Two Canadian researchers hope their work — mapping the cannabis sativa genome — will get rid of the stigma which they say surrounds the cultivation of hemp and marijuana in Canada. University of Saskatchewan's Jon Page and University of Toronto's Tim Hughes hope other scientists will use their work to develop marijuana as a legitimate medical ingredient, and hemp as a high-quality, fast-growing crop.

Psychosis is quite rare – fewer than three in 100 people will experience a psychotic episode in their lifetime. People who smoke or otherwise consume cannabis, especially in significant quantities, have a higher incidence. Some people have vulnerability, a genetic predisposition to psychosis, and cannabis can be a trigger, as can other things like trauma or amphetamines. Severe mental illness like schizophrenia tends to arise in late teens and early adulthood, the same time young people tend to experiment with drugs, so the psychosis can be coincidental. Finally, many people with severe mental illnesses that feature psychotic episodes self-medicate, with cigarettes, alcohol and cannabis.

If Canada’s licensed cannabis producers continue ramping up production at their current exponential pace, there will be more than enough pot to meet the government’s projected demand by the end of 2019, predicts one cannabis researcher who conducted an analysis of the government’s most recent data. While some have suggested shortages in the sector could last for years, Brock University professor Michael Armstrong argues that barring any unforeseen circumstances that supply concerns will be resolved much more quickly than that. Total legal production of cannabis began drastically increasing about six months before legalization, Armstrong notes, as evidenced by how quickly cannabis inventories were growing.

Canada became the second country to make it legal for adults to buy, grow and consume small amounts of marijuana. But it also made it a crime to give it to anyone younger than 19 or 18, depending on the province, and set a penalty of up to 14 years in prison for doing so. At the same time, the government began an $83 million public education campaign, much of it targeting Canadian youths, that warns of pot’s dangers. But persuading teenagers not to see legalization as a green light to use marijuana will be difficult, experts say, not to mention that past antidrug efforts have offered little evidence of success. And when it comes to marijuana and the teenage brain, the science is far from clear.

There is a growing body of evidence to support the use of medical cannabis as an adjunct to or substitute for prescription opiates in the treatment of chronic pain. When used in conjunction with opiates, cannabinoids lead to a greater cumulative relief of pain, resulting in a reduction in the use of opiates (and associated side-effects) by patients in a clinical setting. Additionally, cannabinoids can prevent the development of tolerance to and withdrawal from opiates, and can even rekindle opiate analgesia after a prior dosage has become ineffective.

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A major study into the effects of cannabis on the human brain is at risk of being partially thwarted because too few black users have agreed to take part. White people have come forward in large numbers offering to get involved in King’s College London’s £2.5m study of how the drug may contribute to paranoia and psychosis in some users but not others. It is hoped the project will pave the way for wider medicinal use and make illegal recreational use safer. However attempts to recruit black and Asian people who smoke, vape or eat marijuana have been met with suspicion over how data about illegal drug use will be used and distrust of the establishment.

Cannabidiol, which is an active substance in cannabis, helps relieve the symptoms of schizophrenia by helping to normalize brain metabolism. Schizophrenia is a severe and disabling brain disorder. Professor Markus Leweke, a medical doctor at the Central Institute of Mental Health in Mannheim, Germany, describes the potential benefits of medical cannabis and pharmacological treatments for neuropsychiatric disorders, with a focus on cannabinoids.

Fears that cannabis causes irreparable harm to teenager’s brains have been stoked by trials which “overstated” the effects on intelligence and other functions, according to a review which found little ill-effect after three days abstinence. Studies have shown it is 114 times less harmful than alcohol, but marijuana’s impact on adolescents’ brain development and mental health is a major concern for policy makers in debates over legalisation. This is a key time developmental period and studies have found negative impacts on attention, learning, memory and organisation in heavy or frequent cannabis users. The study found that the “persistence and magnitude of impact” on teenagers had been overblown.

An ingredient in cannabis called cannabidiol or CBD has shown promise in a clinical trial as a potential new treatment for psychosis, scientists said. Scientists conducted a small trial of people with psychosis and found patients treated with CBD had lower levels of psychotic symptoms than those who received a placebo. Psychosis is characterized by paranoia and hallucinations. The study found that they were also more likely to be rated as “improved” by their psychiatrist and there were signs of better cognitive performance and functioning. (See also: An ingredient in cannabis may be useful for treating psychosis – new study)