
Childhood intelligence in relation to major causes of death in 68 year follow-up - gwern
http://www.bmj.com/content/357/bmj.j2708
======
cimmanom
For a community that likes to point out all the time that correlation is not
causation, a lot of the posts so far seem to be making assumptions about
causative direction.

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.

~~~
Houshalter
Well adoption studies show that environment doesn't matter much to IQ. Kids
raised in the poorest families didn't have higher IQs than kids raised in the
richest families ([http://sci-hub.la/10.1007/s10519-007-9142-7](http://sci-
hub.la/10.1007/s10519-007-9142-7)). Adopted siblings have little correlation
in IQ
([https://www.ncbi.nlm.nih.gov/pubmed/21807642](https://www.ncbi.nlm.nih.gov/pubmed/21807642)).
And intervention programs to increase IQ in disadvantaged populations always
fail
([https://www.sciencedirect.com/science/article/pii/S016028961...](https://www.sciencedirect.com/science/article/pii/S016028961500135X)).

Lung cancer is one of the biggest correlation found here. And smoking is
pretty genetic
([https://www.ncbi.nlm.nih.gov/pubmed/15971021](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.

~~~
fao_
> Well adoption studies show that environment doesn't matter much to IQ.

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...](http://sciencenordic.com/adopted-children-have-higher-iqs-their-non-
adopted-siblings)

[https://www.ncbi.nlm.nih.gov/pubmed/6872626](https://www.ncbi.nlm.nih.gov/pubmed/6872626)

[http://www.pnas.org/content/112/15/4612](http://www.pnas.org/content/112/15/4612)

~~~
TangoTrotFox
Your middle link there refers to the Minnesota Transracial Adoption Study [1].
That brief seems to assume the reader is familiar with the studies as
otherwise it would be very easy to misunderstand what they're saying - which
is not what you're saying.

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."._

~~~
TangoTrotFox
I seem to be unable to edit my post. The link was to:
[https://en.wikipedia.org/wiki/Minnesota_Transracial_Adoption...](https://en.wikipedia.org/wiki/Minnesota_Transracial_Adoption_Study)

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

~~~
IntronExon
Paywalls are just s state of mind.

SciHub p, non-paywalled link: [https://dacemirror.sci-hub.la/journal-
article/c16af30ee6a2c0...](https://dacemirror.sci-hub.la/journal-
article/c16af30ee6a2c086f6c7bd85191bbdba/weinberg1992.pdf)

------
pjc50
> Participants 33 536 men and 32 229 women who were participants in the
> Scottish Mental Survey of 1947 (SMS1947) and who could be linked to cause of
> death data up to December 2015.

> 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.

------
maltalex
Interesting.

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](https://en.wikipedia.org/wiki/Flynn_effect)

~~~
danieltillett
Not directly, but it is quite possible the Flynn effect and the increase in
longevity have a common cause.

Shame the Flynn effect ended a few decades ago.

~~~
RubenSandwich
Do you have a source on the Flynn effect ending?

~~~
danieltillett
Wiki has a whole section on it [0].

1\.
[https://en.wikipedia.org/wiki/Flynn_effect](https://en.wikipedia.org/wiki/Flynn_effect)

~~~
RubenSandwich
Thanks, never saw that before.

------
jedberg
Did they control for economic class? If all the smarter people are richer, it
would follow that they lived healthier lives with better access to medical
care.

~~~
pacaro
All participants lived in a society with socialized healthcare built around a
“free at the point of service” model. That’s not to say that socioeconomic
status doesn’t play a part (as other commenters have noted) but the difference
in access to healthcare due to wealth is relatively small in the UK in general

~~~
handelaar
False. All participants were born and took their IQ tests a year before the
very first elements of the NHS came into existence.

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.

~~~
robotresearcher
False? The subjects have lived >75% of their lives with national health. And
the older you are the more you use health services. While it may be the least
good in Scotland, it’s enormously better than being uninsured in the US where
people are understandably reluctant to visit the doctor’s office at all.

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

------
vixen99
It would seem reasonable to suppose that much of this is related to the known
association between delayed gratification (self control) and intelligence (the
marshmallow experiment described as for instance in
[https://jamesclear.com/delayed-gratification](https://jamesclear.com/delayed-
gratification))?

~~~
truculation
And yet intelligent people are said to use more drugs:

[https://www.psychologytoday.com/blog/the-scientific-
fundamen...](https://www.psychologytoday.com/blog/the-scientific-
fundamentalist/201011/why-intelligent-people-use-more-drugs)

~~~
icebraining
It's not clear if they controlled for other factors. It may be that they
simply have more money to buy them.

~~~
pantalaimon
Drugs are not that expensive, but not everyone is so curious to try them.

------
paulpauper
_Figure 4⇓ shows the associations between groupings of childhood intelligence
score (10ths or quarters) and deaths related to 15 specific cancers. About
half of these showed inverse patterns of association with a degree of
linearity, including cancers of the oesophagus, colon or rectum, stomach,
liver, lung, kidney, bladder, and blood. The strongest association was evident
for death related to lung cancer: the risk in the highest performing 10th of
childhood intelligence was reduced by two thirds compared with the lowest
performing 10th. Cancers showing negligible or irregular associations with
childhood mental ability included mouth, pancreas, skin, ovaries, breast
(women only), prostate (men only), and brain or central nervous system._

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.

~~~
Jemm
Or you could say that smarter people don't smoke.

~~~
mathgeek
You could also say that smoking is more popular among poorer populations, the
depressed, those whose parents smoked, etc.

------
pharrington
Here's my hot take: genes that cause a given nervous system to be better than
typical at making decisions that lead to better outcomes for the organism will
cause the organism to be better than typical at cell and DNA repair.

------
mysterypie
Is there a way to express the figures in a more tangible way? Something like:
the smartest 10% lived N months longer than the dumbest 10%.

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%?

------
kelnage
I can’t find any evidence of whether they controlled for obesity (which is
certainly believed to be a factor is several of the diseases that a
correlation was found for). But other than that, I’d say that it is a very
interesting study.

~~~
TangoTrotFox
Low adolescent IQ is a strong predictor for obesity later in life. [1] So I'm
not sure how or why you'd want to control for obesity. You could be looking at
a comorbid effect. Low IQ -> obesity -> early death.

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

------
roryisok
Interesting that suicide had a weak correlation. Intelligence obviously has
little bearing on depression

~~~
mercer
I'm not sure how you got to 'obviously'. Could you elaborate?

~~~
roryisok
Does "weak correlation" not mean that there was very little difference either
way? I just meant this study seems to show that suicide is unaffected by
intelligence. Either I read it wrong or I worded my content badly but I was
just trying to draw a conclusion from what I thought the data said

------
brwsr
There is so much more to this. Inequality, poverty..

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://youtu.be/GvkchZADaaA)

------
amelius
I'd love to see the relation between IQ and happiness.

~~~
jonplackett
Have a look at this, albeit tongue in cheek, survey by card against humanity.

[https://thepulseofthenation.com](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.

~~~
hollander
I can't imagine wanting to be dumb. However, if I got really depressed, then
things may change. Another factor in this is wealth. Does dumb mean poor and
smart rich?

