Cannabis IQ Loss Defended | Weighing Up Sugar
Issue 214 18 - 24 January
In This Issue
IQ & Cannabis
Cannabis IQ impact defended
Teen cannabis use and its effect on IQ have hit the headlines this week in the wake of criticisms levelled at a recentNew Zealand study.In August of last year New Zealand researchers, in collaboration US colleagues, published a study showing heavy and persistent teenage cannabis use led to a decline in IQ.
At the time, the study was lauded as one of the best efforts at untangling the myriad of factors which could influence IQ - thanks mainly to the fact the Dunedin-born participants in the study had been periodically monitored since birth.
This week however, the methods of the study were brought into question by one Ole Rogeberg, a Norwegian economist who published a critique of the study in the journal PNAS. Rogeberg claimed that certain socio-economic factors had not been taken into account and the link between cannabis and IQ - if there was any link at all - might be explained by these factors.
Rogeberg was very direct in his conclusions, stating "It would be too strong to say that the results have been discredited, but fair to say that the methodology is flawed and the causal inference drawn from the results premature."
The authors of the original study were blind-sided by the critique, confessing that neither the journal nor Rogeberg had contacted them about the concerns raised prior to publishing the article.
Nevertheless, they performed further checks on the data to test Rogeberg's assumptions, and found his concerns about the methods unfounded. In a response, the authors stated:
"The paper published today by Rogeberg has raised a seemingly plausible alternative explanation for the finding of an IQ decline in early and heavy cannabis users - but analyses of the Dunedin study data do not support it.
"The most plausible explanation for the data remains that using cannabis from adolescence and into young adulthood contributes to a decline in cognitive ability, as indicated by performance on IQ tests."
While the extra analyses have to some extent rebutted Rogebers claims, there remains some uncertainty over the basis for the causal link.
Lumley, Professor of Biostatistics at The University of
Auckland, commented on the research,
saying, "Even if the association is real and causal there
could still be explanations that don't involve brain
toxicity." He suggested a scenario in which cannabis users
may gravitate to less cognitively demanding situations which
in turn lead to lower IQ.
On the science radar...
Announcing new dates for the SMC's popular media training workshop for scientists: 14 - 15 March in Auckland.
Highlights of the workshops include:
• Newsroom tour
• Q&A with panel of broadcast and print journalists
• Practical tips to increase your confidence with media
• Advice on handling controversy, uncertainty and risk
• On-camera interview practice and feedback
• 'Pitch your story' session to local and national media - put your new skills straight to the test
Places are limited to 12 participants. Active researchers and working scientists (at any stage of their career) are invited to apply before the closing date: Friday 8 February at 6 PM..
Sugar's role in weight examined
Cutting back on sugar may be a bitter pill to swallow for those trying to lose weight, but a new NZ study has confirmed eating less sugar can tip the scales in your favour.
While saturated fats are a well known villain in the obesity saga, the exact impact of other dietary energy sources on body weight has been less clear.
Now, University of Otago researchers, commissioned by the World Health Organisation, have combined and analysed the results from a large number of studies looking specifically at the effects of sugar on body weight.
Their research was published this week in the leading medical journal BMJ.
After searching through nearly 8000 trials and 10,000 cohort studies published internationally, the researchers found 68 studies that directly looked at the effects of free sugars on body weight.
Analysis of the combined results of these studies showed that reducing free sugars in the diet has a small but significant effect on body weight in adults - an average reduction of 0.8 kg. Increasing sugar intake was associated with a corresponding 0.75 kg increase in body weight.
The authors of the research, led by Prof Jim Mann, conclude that "when considering the rapid weight gain that occurs after an increased intake of sugars, it seems reasonable to conclude that advice relating to sugars intake is a relevant component of a strategy to reduce the high risk of overweight and obesity in most countries."
Heading off somewhere exciting?
Scientists, are you departing on voyage of exploration?
Conducting field research in an exotic locale? Or running a fascinating project in your own backyard?
Sciblogs is soon to launch a new 'Field Work' blog, featuring real-time write-ups and photos from scientists on expedition to far-flung places, as well as closer to home, as we round out the field research season.
If you or someone you know may be interested in contributing, get in touch ASAP with email@example.com.
Quoted: The New Zealand Herald
"I think the sugar story has been very confused by people who have exaggerated the badness of sugar.
"Sugar is not inherently a bad substance - if you like a bit of sugar on your cereal, that's fine. What you don't want is an excessive intake of sugar for the amount of calories that you need."
- Prof Jim Mann, Human Nutrition and Medicine at the University of Otago on his latest research into sugar and body weight.
New from the SMC
Cannabis IQ link questioned: Kiwi authors and independent researchers comment on a critique of NZ research linking teen cannabis use to a decline in IQ. A round up of media coverage is also available.
Contagions: Not one, but two infectious diseases have been raising concerns among New Zealand experts as they prepare for the 2013 winter season.
What's causing Australia's heat wave?: Climatologists from the Australian Bureau of Meteorology spell out the situation for the Lucky Country.
A sweet diet: A comprehensive review of research examining the link between sugar intake and weight has confirmed that the sweet stuff plays a role in weight gain and loss.
Some of the highlights from this week's posts:
Kidney Punch and The Dismal Science
"May" advertising - Michel Edmonds takes aim at vauge advertising that uses slippery wording
A new 3 R's for the environment
- Wayne Linklater puts forward a new mantra for
applied ecological science: Reserve, Restore,
What do you think Kiwis die of?
Help Siouxie Wiles out with a side project by reflecting on
our own national mortality for a moment.
Please note: hyperlinks point, where possible, to the relevant abstract or paper.
Biofuel on the
edges: Losing autism symptoms:
There's an (inaccurate) app for that:
Flowerings forecast climate shift: Exceptionally warm spring weather in 2010 and 2012 resulted in the earliest flowering times known in 161 years of recorded history at two sites in the eastern US, according to new research which hints at the impact of climate change.The consequences of such early flowering for plant productivity, pollinators like bees, and ecosystems in general are still unknown.
Journal of Child Psychology and Psychiatry
Biofuel on the edges:Marginal lands - land considered unsuitable for food crops - might be attractive locations for growing biofuel crops. A new analysis have evaluated the potential of marginal lands in the US Midwest to produce biofuel. They report that herbaceous plants grown on marginal lands could produce enough biomass to meet around 25% of US biofuel targets while mitigating direct greenhouse gas emissions.
Losing autism symptoms:Some children who are accurately diagnosed in early childhood with autism lose the symptoms and the diagnosis as they grow older, a new study has confirmed. Researchers took extra steps to ensure that that the initial diagnosis was accurate and the later lack of symptoms was also properly identified.
There's an (inaccurate) app for that:Don't use specialised smartphone apps to diagnose skin cancers, say researchers who tested phone programs claiming to evaluate skin lesion images for melanoma. The researchers tested several apps and found that 3 of 4 applications incorrectly classified 30 percent or more of real melanomas as 'unconcerning'.
Gene hacking:Using only a computer, an Internet connection, and publicly accessible online resources, a team of researchers has been able to identify nearly 50 individuals who had submitted personal genetic material as participants in genomic studies, raising concerns about research and privacy.
Some of the policy highlights from this week:
Groser in Europe: Trade and Climate Change Issues Minister Tim Groser departed for Europe this week to attend international trade and climate change meetings.
Upcoming sci-tech events
• 16th International Conference on
Thinking - 21-25 Jan,
• VII Southern Connection Congress 2013 - 21-25 Jan, Dunedin.
For these and more upcoming events, and more details about them, visit the SMC's Events Calendar.