The Studies Show Tom Chivers and Stuart Ritchie

Many Western countries, most notably the US, had a major decline in their crime rate in the 1990s. About 20 years earlier, the US had banned the use of lead in gasoline. Perhaps you wouldn’t think those two facts are related - but many researchers think this wasn’t a coincidence.
After getting distracted and doing a whole episode on lead and IQ a couple of weeks ago, Tom and Stuart get to the subject they intended to cover: the lead-crime hypothesis. How strong is the evidence that the presence of lead in a child’s early environment increases their propensity for crime when they grow up? And how strong is the evidence that lead removal (at least partly) caused the declining crime rate?
The Studies Show is brought to you by Works in Progress, the magazine full of new and underrated ideas for advancing science, technology, and humanity. They have a new issue out right now, which opens with a fascinating essay on the decline of drink-driving. Check it out at worksinprogress.co.
Show notes
* Numbers on the US crime rate over time
* Evidence from Finland on IQ and crime
* The first study (to our knowledge) on the lead-crime hypothesis, from 2007
* Rob Verbruggen’s 2021 Manhattan Institute report on lead and crime
* Jennifer Doleac’s 2021 Niskanen Center report on lead and crime
* Paper focusing on 1920s/30s America and the impact of lead on crime
* 2020 Swedish paper on moss lead levels and crime
* 2021 PNAS paper on lead and personality change
* 2022 meta-analysis on the lead-crime hypothesis
* 2023 systematic review on the same topic
Credits
The Studies Show is produced by Julian Mayers at Yada Yada Productions.


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Johann Hari is a journalist with an interesting past who has now written four very popular books on scientific topics (addiction, depression, attention, and obesity). Are those books any good?
In this paid-subscriber-only episode of The Studies Show, Tom and Stuart—who have both written reviews of Hari’s books—discuss Hari’s career, his sudden emergence as a science writer, and exactly how many miles you need to travel around the world to ensure your book becomes a New York Times bestseller.

Petrol, pipes, paint: they made a whole generation duller. That’s if you believe the research on the effects of lead on IQ. By interfering with neurological development, the lead that we used to encounter routinely has left hundreds of millions of us with a tiny bit of brain damage.
In this episode of The Studies Show, Tom and Stuart look at the toxic effects of lead - from very obvious, high-dose lead poisoning to the more insidious, low-level effects that have apparently held millions of people back. How strong is the evidence for the effects of low-level lead exposure on IQ?
The Studies Show is brought to you by Works in Progress magazine, a journal of ideas to accelerate human progress. If you’re a student aged 18-22 and want to attend the Works in Progress “Invisible College” this August (at which Stuart is speaking), take a look at this link.
Show Notes
* Centers for Disease Control (CDC) page on lead poisoning
* Articles on the history of lead poisoning from the BBC and the Guardian
* 2022 PNAS study concluding that “half of US population exposed to adverse lead levels in early childhood” (the one with the “824,097,690” figure)
* Article on blood lead levels and which are considered dangerous
* The 2005 meta-analysis on lead and children’s IQs
* Cited in the 2021 “Global Lead Exposure Report”
* The critique from the CDC in 2007
* The critique paper from 2013
* The critique paper from 2016
* The correction from 2019
* The critique paper from 2020
* Quasi experiments: from Rhode Island; using manufacturing employment
* 2018 paper on low-level lead and all-cause mortality
Credits
The Studies Show is produced by Julian Mayers at Yada Yada Productions.


This is a public episode. If you’d like to discuss this with other subscribers or get access to bonus episodes, visit www.thestudiesshowpod.com/subscribe

Preventing cancer. Curing depression. Single-handedly ending the COVID-19 pandemic. Oh, and something to do with your bones. Is there anything Vitamin D can’t do?
Maybe the answer is: “quite a lot”. In this episode of The Studies Show, Tom and Stuart look into the claims about the wondrous powers of Vitamin D supplements - and whether any of them have any decent evidence behind them. The whole story turns out to be a perfect parable for how to think about health research.
📚Buy Tom’s book, Everything is Predictable, at this link! And join us at the book launch in London on 16th May 2024! 📚
The Studies Show is brought to you by Works in Progress magazine: the stylish, well-argued, data-packed place to read essays about science, technology and human progress. Find their latest issue at this link.
Show notes
* Rupa Huq MP’s article from during the COVID pandemic on how the government should be “shouting about Vitamin D”
* Huq and David Davis MP convince the government to recommend Vitamin D
* Stuart’s New Statesman article on why this was jumping the gun a little
* How Vitamin D regulates calcium and phosphorus metabolism in the body
* Might it slow tumour growth? Or prevent cardiovascular disease? Evidence from rats
* Observational studies on how Vitamin D levels are related to: depression, cognitive impairment, cancer rates, cardiovascular disease, all-cause mortality
* Review paper claiming widespread deficiency in Vitamin D
* Scientific American article including discussion of the confusion over what it means to be “deficient” in, and/or have an “insufficiency” of Vitamin D
* 2019 paper reporting results from the VITAL trial on cancer and cardiovascular risk
* D-health trial results on cancer risk and cardiovascular risk
* From the D-health trial, papers reporting no effect of Vitamin D supplementation on: cognitive impairment, depression, microbiome diversity, telomere length, hypothyroidism, erectile dysfunction, falls, fractures
* Classic xkcd cartoon on false-positive jelly beans
* 2022 Nature Reviews Endrocrinology review on the (lack of) evidence for the effects of Vitamin D beyond bone-related problems
* Story of UK man who died of a Vitamin D overdose
* Vitamin D and COVID: the promising observational study; the null trial
Credits
The Studies Show is produced by Julian Mayers at Yada Yada Productions.


This is a public episode. If you’d like to discuss this with other subscribers or get access to bonus episodes, visit www.thestudiesshowpod.com/subscribe

We can all agree that being lonely is bad. But apparently, science shows it’s really, really bad. Indeed, being lonely is so dangerous to your health that its equivalent to smoking 15 cigarettes a day. And it gets worse: we’re in the middle of a loneliness epidemic, meaning that the health of millions is at risk.
In this episode of The Studies Show, Tom and Stuart ask two questions: is there actually a loneliness epidemic? And does it make sense to compare loneliness to something as bad for you as smoking cigarettes?
The Studies Show is brought to you by Works in Progress magazine. Click here to see the latest issue, packed with essays on YIMBYism, clinical research, Russian history, railway tunnels, and more.
Show notes
* The US Surgeon General’s report into “Our Epidemic of Loneliness and Isolation”
* Articles on the loneliness epidemic from the BBC, NPR, the BBC again, the New York Times, the New York Times again, and Science magazine
* 2023 article in The Times (London) that makes the 15-cigarettes-a-day comparison
* The 2017 Jo Cox report on “Combatting Loneliness”
* 2010 meta-analysis of social relationships and mortality risk
* American Time Use Survey, 2003-2020
* Meta-Gallup poll from 2022 on “The Global State of Social Connections”
* Are US older adults getting lonelier (2019 study)? What about “emerging adults” (2021 meta-analysis)?
* Comparison between younger-old people and older-old people on their loneliness levels
* 2017 review study on the health effects of loneliness
* 2023: systematic review no.1, systematic review no.2, both into the effects of loneliness on health
* 2005 study on the health effects of smoking tobacco
Credits
* The Studies Show is produced by Julian Mayers at Yada Yada Productions.


This is a public episode. If you’d like to discuss this with other subscribers or get access to bonus episodes, visit www.thestudiesshowpod.com/subscribe

This is a free preview of a paid episode. To hear more, visit www.thestudiesshowpod.com

The evidence for puberty blockers and cross-sex hormones for young people with gender dysphoria is “remarkably weak”. That’s according to the Cass Review, a new in-depth report commissioned by NHS England.
As you might imagine, the report’s conclusions have been somewhat controversial. In this paid-subscriber-only episode of The Studies Show, Tom and Stuart read through the Cass Report, consider the arguments of its critics, and try to put the whole thing in context.