A 2012 Duke University study made international headlines purporting to find a link between heavy marijuana use and IQ decline among teenagers. Other researchers questioned the findings immediately: Columbia University's Carl Hart noted the very small sample of heavy users (38) in the study. A follow-up study published 6 months later in the same journal found that the Duke paper failed to account for a number of confounding factors. A new study from the University College of London provides even stronger evidence that the Duke findings were flawed.
A recent neuroscience study from Harvard Medical School claims to have discovered brain differences between people who smoke marijuana and people who do not. Such well-intentioned and seemingly objective science is actually a new chapter in a politicized and bigoted history of drug science in the United States. Different-looking brains tell us literally nothing about who these people are, what their lives are like, why they do or do not use marijuana, or what effects marijuana has had on them.
Cannabis rots your brain — or does it? Last year, a paper published in Proceedings of the National Academy of Sciences (PNAS) suggested that people who used cannabis heavily as teenagers saw their IQs fall by middle age. But a study published today — also in PNAS — says that factors unrelated to cannabis use are to blame for the effect. Nature explores the competing claims. (See also: New Research Questions Marijuana’s Impact in Lowering IQ)
The President of the International Narcotics Control Board (INCB), Raymond Yans, has voiced grave concern about the outcome of recent referenda in the United States of America that would allow the non-medical use of cannabis by adults in the states of Colorado and Washington, and in some cities in the states of Michigan and Vermont. Mr. Yans stated that “these developments are in violation of the international drug control treaties, and pose a great threat to public health and the well-being of society far beyond those states”.
Heavy marijuana use is associated with cognitive decline in about 5% of teens, according to a new study, which suggests that the heaviest users could lose 8 IQ points, according to a report, published in the Proceedings of the National Academy of Sciences. If the link is real, the effects on cognition could be dramatic. But intelligence and cognition is affected by a plethora of other factors, including genetic, social and environmental influences that may supersede any influence from drug use.
No serious commentator doubts that cannabis is potentially damaging to the user. Like tobacco, it is typically smoked and thus shares the potential for lung disease. Like alcohol, it affects reaction times and may raise the risk of road accidents. Cannabis has also been associated with cognitive impairment, deterioration in education performance (van Ours and Williams 2008), and psychotic illness (Arsenault 2004). Moreover, cannabis is often – albeit contentiously – seen as a causal gateway to more serious drug use (Kandel 2002). The question is what to do about it?
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.
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.
Robin Room, Peter Reuter (RAND), Wayne Hall, Benedikt Fischer, Simon Lenton, Amanda Fielding
01 September 2008
Despite cannabis being the most widely used illegal drug, and therefore the mainstay of the ‘war on drugs’, it has only ever held a relatively marginal position in international drug policy discussions. Amanda Fielding of the Beckley Foundation decided to convene a team of the world’s leading drug policy analysts to prepare an overview of the latest scientific evidence surrounding cannabis and the policies that control its use. The report of the Beckley Foundation's Global Cannabis Commission is aimed at bringing cannabis to the attention of policymakers and guide decision making.