But why should we assume that just because they're correlated in this study, high IQ causes longer life expectancy?

Maybe the same early childhood circumstances (such as better nutrition) that led to measurably higher IQ also led to individuals being healthier / more robust later in life.

Maybe exposure to certain toxins that decrease IQ (say, lead) also tends to make certain cancers more likely.

Lung cancer is one of the biggest correlation found here. And smoking is pretty genetic (https://www.ncbi.nlm.nih.gov/pubmed/15971021). Other things might be affected by diet and BMI, but that's also highly genetic.

This study also controlled for socioeconomic status.

Really? I remember a few adoption study where they found the opposite: They measured the IQs of genetically identical twins that were adopted into different families, and found that family environment mattered a hell of a lot.

I can't find the study that I remember, but here are some adjacent studies that have done similar things with similar results:

http://sciencenordic.com/adopted-children-have-higher-iqs-th...

https://www.ncbi.nlm.nih.gov/pubmed/6872626

http://www.pnas.org/content/112/15/4612

Their study was a large undertaking studying the differences in black/interracial/white children who were all adopted by wealthy white families in Minnesota. It found that at age 7 the difference in IQ between a adopted white child and adopted black child was 20.1 points. At age 17 this changed to 17.8 points. The difference for a half black child and a white child was 6.1 at age 7, and 8.3 at age 17.

The goal of the study was to show the opposite of what it ended up showing. Consequently many individuals, including the authors of the study themselves, have tried to argue that this is not evidence of a genetic link to IQ. Arguments against it have run the gamut from environmental factors from before the children were adopted (which was at less than 1 years old in all cases) to skin color causing environmental effects. These are certainly contributing factors, however they would undermine any and all results of the study - which is indicative of an after-the-fact effort to undermine their own results. In either case, that result certainly showed nothing like "family environment mattered a hell of alot."

The misunderstanding here probably comes from one questionably phrased sentence in that abstract, "Black and interracial children scored as well on IQ tests as adoptees in other studies." That is more clearly read as "Black and interracial children scored as well on IQ tests as black and interracial adoptees in other studies." In other words, they're comparing differences between 'same group' individuals and trying to see what determines the variance there. And they found that at a young age this is frequently related to environmental factors, whereas at older age genetics becomes dominant even among 'same 'group individuals. In the abstract's rather kinder phrasing, "Our interpretation of these results is that younger children are more influenced by differences among their family environments than older adolescents, who are freer to seek their own niches.".

The study itself is paywalled. And given the decades of controversy it sparked, the Wiki entry is quite expansive.

SciHub p, non-paywalled link: https://dacemirror.sci-hub.la/journal-article/c16af30ee6a2c0...

The ncbi link seems to support my hypothesis, maybe I'm missing something.

Although some people do make me wonder...

For one, with recent advances in genomics, we now realise that conclusions from twin studies in general aren't aging so well. And all the above don't really do genetics, they used seemingly close-knitted cohorts.

In themselves I find all the papers you pointed dubious at best, and more likely garbage. The experimental setups in all of these were rather weak to start with, and did not allow to discriminate between causation and correlation, and the authors all achieved/generalized conclusions that were not supported by their own data.

Our societies fascination and obstination with deriving things from IQ is, well, fascinating... No of these start with asking a question to understand a tractable and useful problem. They're all a my "d!ck is bigger than your d!ck" kind of ranking problem.

> In this prospective cohort study, all individuals born in Scotland in 1936 and registered at school in Scotland in 1947 were targeted for tracing and subsequent data linkage to death certificates

Hard to get a more comprehensive population study than that.

I wonder whether the Flynn effect (increase in IQ in the general population over time [0]) can therefore explain at least some of the increase in longevity in the 20th century.

[0]: https://en.wikipedia.org/wiki/Flynn_effect

Shame the Flynn effect ended a few decades ago.

1. https://en.wikipedia.org/wiki/Flynn_effect

> Sensitivity analyses on a representative subsample of the cohort observed only small attenuation of the estimated effect of intelligence (by 10-26%) after adjustment for potential confounders, including three indicators of childhood socioeconomic status. In a replication sample from Scotland, in a similar birth year cohort and follow-up period, smoking and adult socioeconomic status partially attenuated (by 16-58%) the association of intelligence with outcome rates.

"Men in the least deprived areas of Scotland may live 12.5 years longer than those in the most deprived areas while women in the least deprived areas could expect to live 8.5 years longer than those in the most deprived."

http://www.bbc.co.uk/news/uk-scotland-scotland-politics-2964...

Edit: Interactive visualization of deprivation in Scotland: http://simd.scot/

And health (and all other) outcomes are strongly affected in the UK by geography. On average you'll live in Sussex nearly a decade longer than in Cowdenbeath. In Glasgow as late as the mid-1980s the average male life expectancy was 58 years, and then Scotland had the shit kicked out of it, on purpose, for twelve years, by the 1979 Thatcher government. Cuts in healthcare were inflicted disproportionately-severely on places which did not vote for the Conservatives, and nowhere were they more severe than central Scotland and south Wales.

Nothing you say contradicts the parent’s post. So ‘false’ is incorrect as well as obnoxious.

Poor people eat worse food; don't get as much exercise; and smoke more.

You can predict average life expectancy by post-code, and that's based on socio-economic factors.

How is choosing to smoke more an inequality?

Answers include availability, lack of availability of healthier alternatives, targeted marketing, being missed by anti-smoking campaigns, and peer group influences.

While smoking may be a personal choice, it is not made in a vacuum.

http://journals.plos.org/plosone/article?id=10.1371/journal....

> In the absence of individual level data on socioeconomic status in the full SMS1947, we used school attended as a proxy measure to adjust for potential confounding by background socioeconomic status. A Scottish cohort study has shown that primary school has moderate correlation with paternal social class.

https://www.psychologytoday.com/blog/the-scientific-fundamen...

The problem is higher IQ mean means a healthier lifestyle, which is what protects against cancer, not genes that give rise to high IQ itself. That's why the effect is strongest for smoking, because less intelligent people may be more likely to smoke. Same for drinking, which increases odds of stomach and esophagus and liver cancer. Somewhat disappointing becase it confimrs that we have already suspected, whic his a helathier lifestyle means less risk of certain cancers. Not surprisingly, the effect is non-existent for brain cancers.

This is not the case, see _The association between intelligence and lifespan is mostly genetic_ (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4795559/). The common factor is almost certainly mutational load.

Based on what, exactly?

So the reduction in - for instance - prostate cancer may be due to access to healthcare vs reduction in lunch cancer which might be a proxy for “smarter” decisions.

And with respect to specific cause of death, does a hazard ratio of 0.72 for respiratory disease mean that respiratory disease killed 72 of the smartest 10% each year for 100 of the dumbest 10%?

[1] - http://circ.ahajournals.org/content/124/Suppl_21/A12601.shor...

How many suicides were there in the 60000 studied, perhaps 10? That's not enough to derive a meaningful result, I think.

Edit: My estimate would be roughly correct, sad enough, ignoring my doubts on suicide as a cultural rather than medical category: http://news.bbc.co.uk/2/hi/uk_news/scotland/5297916.stm

Poverty hinders proper brain development and wiring. Life expectance in London is 25 years less for the poor! Economy rules! It is not popular info, but for those interested: https://youtu.be/GvkchZADaaA

https://thepulseofthenation.com

One of he questions was ‘would you rather be dumb and happy or smart and sad’ and then the correlate it with voting for trump.

http://www.independent.co.uk/news/health/intelligence-mental...

On average, just being 'smart' isn't sufficient.