With the widespread availability of marijuana in recent years thanks to its legalization in a growing number of states, there has been increasing concern about the long-term health consequences on teens who might be able to get easier access to it illegally. A study published by the American Psychological Association in the journal Psychology of Addictive Behaviors should alleviate some of the worst fears. The researchers found no links to physical or mental health issues -- including depression, psychotic symptoms or asthma -- in any group, even those with very high use.

Few individuals have as much influence on drug policy in the United States as Nora Volkow, Director of the National Institute on Drug Abuse (NIDA), whose tenure at the head of the federal government’s top drug research institution started in 2003. In a new interview, Dr. Volkow came to admit that she was wrong about her expectations relating to the legalization of marijuana and that pro-legalization advocates were in the right. Ethan Nadelmann, founder of Drug Policy Alliance and pro-marijuana activist, challenged Volkow on his show. Volkow acquiesced, admitting, “I was expecting the use of marijuana among adolescents to go up, but overall, it hasn’t.”

Teenagers who use cannabis daily before the age of 17 are more than 60% less likely to complete high school or university, research published in Lancet Psychiatry found. The researchers called for their findings to be considered in cannabis legalisation reform. Alex Wodak of the Australian Drug Law Reform Foundation said the evidence for the harms of frequent use in the study was "compelling" but added daily use before age 17 would be "pretty uncommon". Many studies show that prohibiting cannabis did not make it any less easy for young people to get hold of it. (See also: How much pot does it take to turn a teenager into a suicidal dropout? | Linking cannabis and suicide doesn't prove causation | Cannabis use in teens, suicide and school dropout: the jury is still out)

While no psychoactive substance is completely harmless, modern science continues to prove that cannabis is one of the safer and more effective therapeutic agents available. Here’s a look back at some of the most significant marijuana-centric studies published over the past year. The cumulative use of cannabis by adolescents has no ill effect on intelligence, according to longitudinal data published in January in the Proceedings of the National Academy of Sciences. Investigators concluded: "In the largest longitudinal examination of marijuana use and IQ change,... we find little evidence to suggest that adolescent marijuana use has a direct effect on intellectual decline.”

An alarming rise in drug-related deaths at music festivals can be countered by testing illicit substances onsite, according to the first academic study of its kind, which has triggered calls for similar services to be rolled out at all major events. Testers found that one in five substances sold at the Secret Garden Party, a four-day festival in Cambridgeshire in July 2016, were not as described by dealers. Chemists from the non-profit social enterprise The Loop analysed 247 drug samples brought in anonymously by festivalgoers. Two-thirds of people who discovered they had had substances missold to them subsequently handed over further substances to the police, according to the study. (See also: Pill testing could save lives – so why are we letting people die?)

As the legalization of recreational cannabis gains traction across North America, one of the most-debated health concerns is psychosis and cannabis use, particularly for young people. Frustratingly, both sides often resort to cherry picking data or conflating correlation with causation. Anecdotes, not science, often prop up these arguments. We’ve all heard it: “Consuming cannabis can lead to psychosis.” While this is partially true, it reflects only a restricted, conveniently framed piece of the picture. Others dismiss the association completely, which is also not productive to evidence-informed conversation. For the most part, we’re getting the conversation wrong, and doing a disservice to young people, caregivers, people experiencing psychosis, and those at risk. 

Within the last decade the hitherto little known psychoactive substance of khat has emerged as a regional and international issue. In the Horn of Africa khat production has spurred an economic boom, but dramatic increases in consumption have raised public health concerns. Given the complexity of the topic spanning multiple academic disciplines and fields of professional practice, the need for a systematic overview is urgent.

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Cannabis dependence is a disorder primarily experienced by young adults, especially in higher income countries. It has not been shown to increase mortality as opioid and other forms of illicit drug dependence do. Our estimates suggest that cannabis use as a risk factor for schizophrenia is not a major contributor to population-level disease burden.

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Half a century ago, Hebrew University Prof. Raphael Mechoulam isolated and synthesized THC, the main psychoactive compound in the cannabis plant. By 1963, Mechoulam and his research partners had revealed the structure of cannabidiol (CBD), a key ingredient in cannabis. By the following year they had isolated THC for the first time, established its structure and synthesized it.

Decriminalizing cannabis doesn't lead to more widespread use, according to a study comparing cannabis users in two similar cities with opposing cannabis policies — Amsterdam, the Netherlands (decriminalization), and San Francisco, California (criminalization). The study compared age at onset, regular and maximum use, frequency and quantity of use over time, intensity and duration of intoxication, career use patterns, and other drug use. No evidence was found to support claims that criminalization reduces use or that decriminalization increases use.

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Decriminalizing cannabis doesn't lead to more widespread use, according to a study comparing cannabis users in two similar cities with opposing cannabis policies — Amsterdam, the Netherlands (decriminalization), and San Francisco, California (criminalization). The study compared age at onset, regular and maximum use, frequency and quantity of use over time, intensity and duration of intoxication, career use patterns, and other drug use. No evidence was found to support claims that criminalization reduces use or that decriminalization increases use.

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Marijuana has been shown to have both anxiolytic (anti-anxiety) effects and to induce anxiety and psychosis in certain people. In schizophrenics, it can increase symptoms, and in healthy people it can increase the risk of schizophrenia. Now, new study shows that the two active ingredients in pot, ?9-tetrahydrocannabinol (THC) and cannabidiol (CBD) may have quite opposite effects on the brain – and behavior – and could explain why pot’s effects can be unpredictable.

Dr David Potter and GW Pharmaceuticals – a company that is exploring how cannabis could help treat a range of illnesses ranging from epilepsy to cancer – have turned their attention to developing a cannabis-based treatment for psychosis and related illnesses such as schizophrenia. For a drug that is widely seen as a trigger for acute psychotic illness in young users, this at first sounds preposterous. But, as Potter explains, the cannabis plant is much more than just a psychedelic weed. A cannabinoid known as CBD (or cannabidiol) appears to have almost the exact opposite effect.

You may have heard that marijuana is a gateway drug. New research in the Journal of School Health could shed some light on this question. They found that "the vast majority of respondents reported using alcohol prior to either tobacco or marijuana initiation." Not only that, but of those three main substances -- alcohol, tobacco and marijuana -- kids were the least likely to start using pot before the others. "Alcohol was the most widely used substance among respondents, initiated earliest, and also the first substance most commonly used in the progression of substance use," the researchers concluded.

While the world seemed to arrest, the cannabis industry’s pulse grew stronger. Cannabis research, though temporarily stymied as universities scrambled to get COVID-19 protocols in place, continued to plod ahead. Although the number of cannabis-related publications were down in 2020 compared to the previous year (what wasn’t, other than stock market indices?), scientists continued to unlock the mysteries of the fascinating plant. Here are some of the top stories in cannabis research in 2020. Italian scientists isolated a new cannabinoid, THCP (tetrahydrocannabiphorol), and cannabinoids may treat symptoms of Parkinson’s disease

Columbia professor Carl Hart: "The National Institute on Drug Abuse funds 90 percent of the world's research on drug abuse with our tax dollars. The mission of NIDA is to focus on pathology, or drug addiction.... You have this disproportionate focus when, in fact, 90 percent of the people who use marijuana smoke it with no problems." (See also: Black leaders were misled about marijuana, Columbia professor says)

The World Health Organization’s (WHO) Expert Committee on Drug Dependence (ECDD or Expert Committee) released in January 2019 the outcomes of the first-ever critical review of cannabis, recommending a series of changes in the current scheduling of cannabis-related substances under the UN drug control conventions. Eagerly awaited, the ECDD recommendations contain some clearly positive points, such as acknowledging the medicinal usefulness of cannabis by removing it from Schedule IV of the 1961 Single Convention on Narcotics Drugs; clarifying that cannabidiol (CBD) is not under international control; and addressing some long-standing scheduling inconsistencies.

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In the scientific literature, 'skunk' has come to mean something more specific: cannabis that contains a high percentage of Tetrahydrocannabinol (THC, the intoxicating part) but little to no Cannabidiol (CBD, an antipsychotic), in contrast to other milder ‘strains’ which contain lower levels of THC and more a significant CBD component. Skunk is a deliberate creation of the illicit industry, fashioned by generations of selective breeding and advanced cultivation methods that have steadily pushed THC levels up over the last 20 years.

There is no evidence that tough policies deter young people from using cannabis, a study has found. Analysing data about cannabis use among more than 100,000 teenagers in 38 countries, including the UK, USA, Russia, France, Germany and Canada, the University of Kent study found no association between more liberal policies on cannabis use and higher rates of teenage cannabis use. “My new study joins several others which show no evidence of a link between tougher penalties and lower cannabis use,” said Prof Alex Stevens, from the University of Kent’s school for social policy, sociology and social research.

According to a research study published by the University Of New Mexico and Releaf App in the Yale Journal of Biology and Medicine,cannabis flower may be effective in providing immediate relief for the symptoms of depression – a condition affecting roughly 1 in 5 adults in the U.S., and often leading to other ailments like cancer, substance use disorders, anxiety disorders, schizophrenia, dementia, diabetes, cardiovascular disease, and chronic pain. “The findings suggest that, at least in the short term, the vast majority of patients that use cannabis experience antidepressant effects, although the magnitude of the effect and extent of side effect experiences vary with chemotypic properties of the plant,” the paper reads.