February 08, 2007
Intelligence Boosting Gene Ups Schizophrenia Risk

Some serious engineering trade-offs came with making humans more intelligent.

Most people inherit a version of a gene that optimizes their brain's thinking circuitry, yet also appears to increase risk for schizophrenia, a severe mental illness marked by impaired thinking, scientists at the National Institutes of Health's (NIH) National Institute of Mental Health (NIMH) have discovered. The seeming paradox emerged from the first study to explore the effects of variation in the human gene for a brain master switch, DARPP-32.

The researchers identified a common version of the gene and showed how it impacts the way two key brain regions exchange information, affecting a range of functions from general intelligence to attention.

If higher intelligence was a longer running trait in the human species it is unlikely that we'd have IQ-boosting genetic variations that come with such serious downsides. Bad side effects of genes that provide some benefit are usually a sign that the genetic adaptation in question is a recent response to a recent selective pressure.

Three fourths of subjects studied had at least one copy of the version that results in more efficient filtering of information processed by the brain's executive hub, the prefrontal cortex. However, the same version was also more prevalent among people who developed schizophrenia, a severe mental illness marked by delusions, hallucinations and impaired emotion that affects one percent of the population.

"We have found that DARPP-32 shapes and controls a circuit coursing between the human striatum and prefrontal cortex that affects key brain functions implicated in schizophrenia, such as motivation, working memory and reward related learning," explained Andreas Meyer-Lindenberg, M.D.

"Our results raise the question of whether a gene variant favored by evolution, that would normally confer advantage, may translate into a disadvantage if the prefrontal cortex is impaired, as in schizophrenia," added Daniel Weinberger, M.D. "Normally, enhanced cortex connectivity with the striatum would provide increased flexibility, working memory capacity and executive control. But if other genes and environmental events conspire to render the cortex incapable of handling such information, it could backfire -- resulting in the neural equivalent of a superhighway to a dead-end."

I expect when offspring genetic engineering becomes widespread people will have to face many tough questions about how to weigh the benefits and risks of large numbers of genetic variations they could give their offspring. Some humans are not cognitively well designed to model complex trade-offs that involve probabilities I expect a lot of bad decision-making by prospective parents.

Share |      Randall Parker, 2007 February 08 11:23 PM  Brain Genetics

Lono said at February 9, 2007 8:05 AM:

This subject is of particular interest to me because I have OCD.

My OCD causes me to read compulsively and it over stimulates some areas of my brain involved in higher reasoning.

This in many ways may seem ideal - except that OCD also causes distracting, stressful, and anti-social ritualistic behaviors.

However, I would have an extremely hard time trading some of my intelligence away to eliminate these disadvantageous traits.

That being said, above average intelligence can itself be quite a burden in modern American society - as it is seen as a largely undesirable trait by those who govern.

David A. Young said at February 9, 2007 9:28 AM:

"I expect a lot of bad decision-making by prospective parents."

And this would be something new??? :-)

Kralizec said at February 9, 2007 1:05 PM:

"I expect a lot of bad decision-making by prospective parents."

It seems probable that there will be much good, bad, and middling decision-making by prospective parents, law-makers, executives, regulators, businessmen, celebrated writers, political founders, and tyrants. Moreover, since the good seems always to be good for someone, it seems that many decisions will be good or bad, depending on the person whose benefit or harm is under consideration.

I think we can reasonably foresee the rise of genetic artists who will seek fame for the splendor of their products. Biographers may describe or explain these artists in terms of the development of their works through time and the "periods" of the artists. Some genetic artists will publicize and lay claim to their works at the end of their life or posthumously, when they can no longer be harmed and their work can no longer be stopped. And I do wonder if foundations will be made along the lines of the Bene Gesserit and Bene Tleilax in Frank Herbert's Dune novels. It's the subterranean, long-term projects, the consideration of which causes me pain, the projects that will come to their splendid or depraved, or splendid and depraved, fruition after I'm dead. The eternal return is cold comfort.

Dave said at February 9, 2007 9:18 PM:

"Scientists Discover Parallel Codes In Genes"
"Our findings open the possibility that genes can carry additional, currently unknown codes"


quitacet said at February 9, 2007 10:25 PM:

reminds me of that article about ashkenazi jews in the economist a while back

N. Jim said at February 10, 2007 9:11 AM:

If higher intelligence was a longer running trait in the human species it is unlikely that we'd have IQ-boosting genetic variations that come with such serious downsides.

Surely it depends on how intelligence works, and how this variation works. You might almost as easily say that if bipedalism were a longer running trait, then taller people wouldn't be prone to having back problems.

Randall Parker said at February 10, 2007 10:44 AM:


But people were so poorly fed in the past they were not as tall. Plus, lots of people are shorter genetically. The selective pressure for tallness might also be recent. So it also might produce effects that wouldn't show up if the trait was around for a longer period of time.

Sickle cell anemia and beta thalassemia are examples of fairly recent genetic adaptions (both to malaria) will have serious side effects. We have others in the human race. For example, the higher altitude people of the Himalayas and an area in Ethiopia have much better mutations for high altitude living than the Andes Amerinds. Why? The Amerinds have been in the Andes for a much shorter period of time. They've got the first easier mutations to get (e.g. thicker blood) that have downsides. The other two groups have had thousands, perhaps tens of thousands, of years more to come up with mutations that better suit them to high altitude with fewer downsides in their adaptations.

Randall Parker said at February 10, 2007 10:53 AM:

Kralizec says something very likely in our future:

I think we can reasonably foresee the rise of genetic artists who will seek fame for the splendor of their products.

Some will be exhibitionists who will go after exhibitionist parents who want to have very unusual (yet mostly very attractive) children. Others will be artists along more classical lines of beauty. It had never occurred to me before but we should see some serious works of beauty produced by offspring genetic engineering.

But we'll also see creation of pretty extreme products of genetic engineering to produce parts to alter the appearances of adult and adolescent humans.

Dale Fitz said at February 10, 2007 12:11 PM:

Although schizophrenia is mostly maladaptive, the unique perspective it confers on the people who suffer from it is in some ways advantageous. Think of van Gogh, or John Nash. Their ability to view the world through such a skewed lens had a lasting impact on the rest of the world. Without such free-thinking people, culture would advance far more slowly. Many great thinkers and creators suffer from some sort of mental illness, and I am sure that a much larger portion of the "world changing" thinkers of history suffered from mild forms of OCD or schizophrenia. Perhaps it is only the extreme cases that are harmful, whereas mild forms of these mental illnesses are actually advantageous to the propagation of the species, which would help explain why it continues to be a common genetic variation.

rsilvetz said at February 11, 2007 7:48 AM:

Forgive me for being the one to point this out -- but most high intelligence individuals are normal. One should not infer from this research or the research on the Ashkenazi Jewish population the general proposition that there is somehow an issue with high IQ and disturbed consciousness. Which is at the root of the worry that folks are going to make poor choices in the genetic engineering arena.

While it would be nice to produce a whole society of IQ 180 babies by ripping off the Ashkenazi Jewish genes, nobody of sane mind would risk it. The fact that some will is also not some big worry. The majority will follow the obvious path to rip off the plethora of gene combinations that produce individuals in the 140-180 range without known side-effects.

wcw said at February 12, 2007 11:03 PM:

I know it's an article of faith that IQs of 140-180 are special, but if you control for the manifold things clearly unrelated to actual smarts that skew that measure (like, you know, parental income), they really aren't. It isn't that "high-intelligence individuals" are normal, it's that high intelligence is normal.

Somehow repair US society to educate everyone and not just the 10% with good nutrition born to the well-off and -educated and you likely do more for measured aggregate IQ than inserting the appropriate genes in every newborn in the country.

Joshua Allen said at February 13, 2007 10:06 AM:

Dale: I agree. I believe that idolotary (in the general sense; the insistence on placing too much stock in the reality of symbols) is genetic; and there is a genetic basis for instinctive rejection of idolotary.

wcw: "high" is a relative term, it makes no sense to say that "normal" is "high". And the "intelligence" discussed in this report has NOTHING to do with education. It's a genetically endowed biological efficiency in prefontal cortex processing efficiency. If you can find a way to educate people to give them a faster pfc, o educate them to be taller, let me know. And blaming "broken society" is a lousy excuse. Start by tutoring the kids next to you rather than grousing about the "broken system", and maybe we'll start educating our kids half as well as India and China, who spend 1/100th what we spend.

rsilvetz: the issue is that when people disturb the natural selection process by aggressively rationally selecting for certain traits, they screw up other things. This has been going on for 10,000 years at least. Only difference is now we can do it way faster. We needn't enslave and rape other races, we needn't have the king keep harems and wet nurses, and etc. We can just select the genes from a menu. Ruthless deliberate selection (sometimes known as the "sexy son effect") has led to all sorts of skews in the human race. But the last 10,000 years were just the beginning.

Mthson said at February 13, 2007 4:10 PM:

Wcw: We have examples of what really 'nice' societies look like where everyone receives a lot of a care in countries like the Scandinavian countries, but they haven't shown a heightened proportion of individuals in the higher IQ range.

Randall Parker said at February 13, 2007 7:12 PM:


Adoption studies have produced results which contradict your assertion of the primacy of environment in determining IQ. Environment has a bigger influence in a place like Africa where lots of people are sick and hungry. But in the United States adoption studies show very little influence on adult IQ from adoption into different status families at a very young age.

Joe said at August 16, 2007 9:51 AM:

Am I missing something. Schizophrenia is a byproduct of man's ability to do scientific research. Does this mean that the cure for schizophrenia is to stop doing research. Or is it because we learned how to use fire to cook our meat. Given the choice between eating some barbecue ribs and living in fear of catching schizophrenia, I'm gonna take the ribs.

Mikhail Mehra said at March 29, 2010 4:28 AM:

I have been pondering the relationship between schizophrenia and intelligence for a while now, i have no real scientific knowledge of how the brain functions, but you have to admit that intelligence and schizophrenia have to have a proportional relationship, schizophrenia seems like a higher level of consciousness in the brain, increased brain function, increased connections between the brain etc and the crazies we see are simply people who cannot come to understand their situation(because society really doesnt know, and rather than help channel or understand something like what a schizophrenic is going through society would label that individual and repress it which is exactly what you should not do) and lose control of it or someone who does understand the situation but anyway gets lost in it, i dont usually like to bring up lsd for all the preconceived notions attached to it but really, like an lsd trip! If you fight it or try to repress it you only get more lost in it and it only gets worse, you have to embrace it channel it, so basically either you go by what your psychiatrist says which is that its schizophrenia and try to change the brain you have been given by evolution or you channel it for better, as with every evolutionary pattern.

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