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Confounder Of The Day: How Sexy Your Parents Were

One of the more interesting mental health results is the differing prevalence of psychiatric disorders depending on the age of the patient’s parents. This month’s JAMA Psychiatry includes a study from Denmark that conducts one of of the largest and most rigorous analyses of this effect and finds that a whole host of psychiatric diseases are more common in people born of young mothers and old fathers.

The young mother effect should be pretty straightforward. Poor women are more likely to have children at a younger age and some psychiatric diseases are more common among the poor. Women with psychiatric disorders can be more impulsive, which results in more unprotected sex and teenage pregnancy and hence children at a younger age; the children then inherit these genes and get psychiatric disorders of their own. No surprises here.

The old father effect has a potentially more interesting explanation. The male reproductive system, unlike the female reproductive system, produces gametes throughout the reproductive lifetime. Presumably older people have more time for mutations to accumulate. Some of these mutations are random, the result of passing cosmic rays or environmental toxins. Others are theorized to be a result of sex cells undergoing “selfish spermatogonal selection”, a hypothesized sorta-cancer-like process in which some sperm progenitor cells develop “selfish” mutations that increase their relative prevalence in the testes at the cost of the quality of sperm they produce – greater paternal age provides more time for this process to happen. The children of older fathers therefore end up with a higher mutational load and more likelihood of mental disorders – not to mention a host of other issues like lower IQ, less physical ability, decreased health, et cetera. It’s very plausible and according to the Danish study the child of a 45 year old father is 1.5x more likely to develop schizophrenia and 1.8x more likely to develop autism compared to the child of a 25 year old father – not a subtle effect!

But the JAMA Psychiatry study references another study, this one really clever, that casts doubt upon this finding. Petersen et al, also from Denmark (which keeps really good track of its mental health and so hosts a disproportionate number of epidemiological psych studies) proposes a much more prosaic explanation.

They find that the mental health of a child depends less on how old her father was when she was born than on how old her father was when he had his first child. In fact, after adjusting for the former effect, the latter completely disappears! For example, if Bob had Child 1 at age 20 and Child 2 at age 40, and Dan had Child 1 at age 39 and Child 2 at age 40, Dan’s second child is at higher risk for mental disorders than Bob’s, even though they both have fathers of the same age – and Bob’s younger child is at no higher risk of disorders than his eldest.

Petersen et al don’t do a great job of coming out and saying it, but I think they hypothesize that the impairments associated with mental disorders – or just the poorly functioning genes that put someone at risk for mental disorders – make it harder for a man to find a partner and start having kids. To be crass about it, if a man has dysfunctional tendencies his value on the marriage market goes down and he’s got to wait longer before he finds people willing to have children with him.

This is sad on a general level. It suggests that guys suffering from mental disorders are unlucky in love in the same way they’re probably unlucky in a lot of other things. And it means society loses what could have been a useful piece of advice for cutting psychiatric disease.

But it’s nice and liberating on a personal level. Here I am at thirty years old, unmarried, childless, and there is no way I am going to try to have kids for the next four years while I’m doing my residency. There are a couple of people in my class right now having babies – women, in fact! – and the idea of doing two of the most stressful and time-consuming things you can go through simultaneously makes my head spin. Now I get to feel a little less guilty about waiting.

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67 Responses to Confounder Of The Day: How Sexy Your Parents Were

  1. ozymandias says:

    It’s interesting that mental disorders make men less sexually attractive and women more sexually attractive. Hypotheses I generated off the top of my head:

    (1) maybe men have a preference for mentally ill women (the “crazy bitch” phenomenon)?
    (2) men in general like casual sex more than women do; maybe they’re willing to trade off mental stability for an easy lay. If this is true we’d expect most of the mentally ill women with children to not have a male partner.
    (3) maybe something about gender differences in mental illnesses? Although I’m not sure why depression would make you more likely to get laid than alcoholism, or antisocial personality less likely than borderline personality.

    • moridinamael says:

      Alternative hypothesis: A man with let’s say “apparent” mental illness will not procreate when he’s young because he’ll drive off any mates, but if he struggles his whole life, attains finincial and social stability despite his illness, he might find a younger, lower-status poor woman who will procreate with him.

      A woman with let’s say “apparent” mental illness will not procreate when she’s young because she’ll drive off any mates, and if she struggles her whole life, attains finincial and social stability despite her illness, she STILL won’t procreate because she’s a woman and she’s probably either significantly less fertile or just culturally less acceptable as a mate because “ew old women.”

      Edit: to clarify, I don’t read the data as indicating that mental illness makes women more sexually attractive and men less sexually attractive. I read it as saying that it makes everyone less sexually attractive when young and then that stigma is only removed for some subset of older men.

      • dhill says:

        “I read it as saying that it makes everyone less sexually attractive when young and then that stigma is only removed for some subset of older men.”

        @moridinamael Say that to porn industry, they must have gotten something seriously wrong.

    • Benquo says:

      2 seems most probable to me. Attractiveness need have nothing to do with it. In a “men bid, women accept or reject” system, mentally ill women are worse at rejecting (partly because of less impulse control, partially because of fewer mental defenses, partially because of lower status), so they end up with partners sooner than other similarly attractive women. This is similar to 2, but I don’t think it’s quite the same because it doesn’t *require* impregnation through casual sex as a mechanism.

      I am sad that this is the most plausible hypothesis, though. It would be a nicer world if this could be explained by saying that BPD and depression are hott.

    • Scott Alexander says:

      Yes, I agree with Benquo’s version of hypothesis 2.

    • Anonymous says:

      >It’s interesting that mental disorders make men less sexually attractive and women more sexually attractive.

      Wait, where’d you find that?

      (If you are making an inference from the young-mother-mental-illness connection, I’m not sure you should assume that genders behave similarly here. If a woman’s “value” on the “reproduction market” peaks earlier then men’s, a woman who reproduced at a young age would be under the same lax-selection-effect as a man who reproduced at an old age. Also, confounds already mentioned by Scott.)

  2. Deiseach says:

    The young mother effect should be pretty straightforward. Poor women are more likely to have children at a younger age and some psychiatric diseases are more common among the poor.

    Hmm – how about older men in second or even third marriages to younger women? I mean, it might be reassuring to think it’s all down to “crazy poor young women are the reason older men have crazy kids” but let’s not go back to Freud and Blame The Momma For Junior Being Trouble, okay? Unless the Danish analysis finds that exclusively it’s poor young women having children with older guys, let’s not write them off that easily. Socially, with no-fault divorce and longer life spans, it’s become more acceptable and easier for men to enter into second or third marriages, and it’s always been easier for older men to find younger women as spouses rather than vice versa (just look at Johnny Depp, 50 and his new partner Amber Heard, 27 which makes her young enough to be his daughter. Should they have a child together, as may well happen, can she really be classed as one of the poor young women with bad impulse control and/or psychiatric conditions in your hypothesis?)

    The second study is interesting, and I’d like to know more if it bears up what you conclude: that the reason for older first-time fathers may be that they’re the losers in the mating game due to deficiencies including mental problems, and that this is what is passed on to when they reproduce.

    Except doesn’t that contradict your first presumption? If crazy poor young women are impulsively having unprotected sex with unsuitable partners, then couldn’t some of those unsuitable partners be those same losers? Who managed to hook up with a woman who wasn’t too fussy at least once in their twenties or early thirties and have a kid by her?

    What I’m saying is, this sounds a little bit like “eat your cake and have it”. Younger women and older men having children with higher chances of mental problems? The women are poor, crazy and impulsive so they’re having kids early. The men may also be poor, crazy and impulsive, so they’re – having kids later?

    In short, “lay not that flattering unction to your soul” that you can afford to put it on the long finger if you want to have a child. It may be that for men, as for women, earlier is indeed better to have a child.

    • Scott Alexander says:

      I am confused by your first theory. While older men do sometimes marry younger women, surely the fact that a woman is young is, all else equal, correlated with her partner being young rather than vice versa.

      For your second point, see Ozy’s comment above and Benquo and my responses.

      • Deiseach says:

        Well, quick trawling around on the internet reveals some very odd statistics, e.g. best chance of a first marriage lasting more than 10 years is if there are no children.

        There’s a very detailed study but it’s all about women (I’d like to see the equivalent results for men, and they don’t seem to have measured any kinds of mental problems other than Generalised Anxiety Disorder).

        Result for that:
        Women who had ever had GAD reported that they had suffered for at least 6 months from worry or anxiety, including feelings of restlessness, feeling keyed up or on edge, irritability, a pounding or racing heart, getting tired easily, trouble falling or staying asleep, and feeling faint. GAD is associated with a greater chance of first marriage, although the difference disappears by age 30. GAD is also associated with a greater likelihood of cohabitation disruption, a greater likelihood of first marriage disruption, and a greater likelihood of second marriage disruption.

        But it doesn’t mention if GAD is associated with “more likely to have children/had children earlier”, which is what you seem to be arguing above: the young mothers with older male partners (whether married or not) having children.

        That’s what I was objecting to: you jumped, without any reason to do so (except extrapolation) that I could see, to “young mothers = poor mothers = crazy mothers = is why their kids are more likely to have mental problems”.

        What I tried to say is that we don’t know this for a fact. There are more second and subsequent marriages nowadays, and the fact of the matter is that it’s easier for older men to find younger wives than for older women to find younger husbands:
        The likelihood that divorced women will remarry has been declining since the 1950’s, when women who divorced had a 65 percent chance of remarrying. Data for 1995 show that women who divorced in the 1980’s only had a 50 percent chance of remarrying.

        Whether or not these younger women married to older men who are on their second marriages are, or have, mental problems to pass onto their kids is not established.

        I’m not arguing against the fact that poorer people suffer more from untreated health problems; that young women with mental health problems behave impulsively and recklessly, including having children early by (perhaps) multiple partners; that such young women may be more likely to settle for older, ‘deficient’ male partners than ‘normal’ women of their age, or that this means a higher risk for their kids of developing health problems.

        What I am arguing against is (what seemed to me to be) the assumption that “Well, I’m okay to put off my child-begetting to a later date because I’m not going to be a deficient older male since I’m not a crazy loser”.

        Unless the Danish study correlates that yup, all the older fathers are losers and all the younger mothers are poor crazy women, you can’t forecast that with certainty.

        • Deiseach says:

          The U.S. census has some excellent data for number-crunching. According to the 2000 census, the ratio of unmarried men per 100 unmarried women (population ages 15 and over) is 86.

          So there are more single women than single men, due to never married/divorced/bereaved.

          According to the Marital Events of Americans: 2009American Community Survey Reports (issued August 2011).

          Variations in rates between men and women can be attributed to gender differences in marriage. Women tend to live longer than men. Women also tend to marry older men. Consequently, widowhood rates were higher for women. Men also remarry more than women do, so men’s marriage rates were higher than women’s rates.

          Percentage of population married:

          15-24 years Men 19.5% Women 27.9%
          25-34 years Men 43.9% Women 41.8%
          35-44 years Men 18.3% Women 15.8%
          45-54 years Men 10.8% Women 9.4%
          55-64 years Men 5.0% Women 3.7%
          65 and over Men 2.4% Women 1.4%

        • Deiseach says:

          The U.S. census has some excellent data for number-crunching. According to the 2000 census, the ratio of unmarried men per 100 unmarried women (population ages 15 and over) is 86.

          So there are more single women than single men, due to never married/divorced/bereaved.

          According to the “Marital Events of Americans: 2009 American Community Survey Reports (issued August 2011)”:

          Variations in rates between men and women can be attributed to gender differences in marriage. Women tend to live longer than men. Women also tend to marry older men. Consequently, widowhood rates were higher for women. Men also remarry more than women do, so men’s marriage rates were higher than women’s rates.

          Percentage of population married:

          15-24 years Men 19.5% Women 27.9%
          25-34 years Men 43.9% Women 41.8%
          35-44 years Men 18.3% Women 15.8%
          45-54 years Men 10.8% Women 9.4%
          55-64 years Men 5.0% Women 3.7%
          65 and over Men 2.4% Women 1.4%

          So from this, we see that for women, very roughly the age range of marriage peaks from 15-34, while for men it peaks from 25-44.

          See, this is what I’m arguing with you about. Your presumption that “The young mother effect should be pretty straightforward” can be explained by reversing “poor people tend to have more psychiatric/more untreated psychiatric problems; poor parents tend to be younger parents” to be that “ergo, young mother = poor and much more likely to be crazy mother”.

          I’m saying no, this is the natural distribution of how marriage shakes out: younger women, older men. There need not be a huge age gap between “younger” and “older”; obviously, the older the first time father, the more degraded the sperm, but this does not mean “Well, we nice healthy educated middle-class professionals don’t have to worry about delaying having children; it’s only the poor crazy underclass who suffer this effect”.

          Some, at least, of the effect must be down to ‘men are older when they marry’ and ‘older men on second or third marriages’, not simply “The young mother effect should be pretty straightforward.” and “I think they hypothesize that the impairments associated with mental disorders – or just the poorly functioning genes that put someone at risk for mental disorders – make it harder for a man to find a partner and start having kids. ”

          Dan in your hypothetical could be an older man who delayed having kids because he and his first wife were busy building their careers, and he is now a first-time father with his second, younger wife – it has been known to happen!

          Whereas Bob could have been a poor guy who had his first kid when he was 20 because he married (or cohabited) young and the second kid at 40 was an unplanned pregnancy. This seems to me at least as likely as Dan being a loser guy who hooked up at long last with a young crazy chick who recklessly got pregnant twice in close succession by him, while Bob was an educated professional who was such a stud he had his first kid while in college, then got responsible and delayed his second child to a more mature and established age.

        • Scott Alexander says:

          “What I am arguing against is (what seemed to me to be) the assumption that “Well, I’m okay to put off my child-begetting to a later date because I’m not going to be a deficient older male since I’m not a crazy loser.”

          No, that’s definitely not what I was saying.

          I was originally worried about putting off child-bearing because I thought greater age of childbearing *caused* mental disease.

          Now I am not worried about it, because it looks like greater age of childbearing *indicates* bad genes which cause mental disease.

          In other words, I don’t know if I’m a crazy loser or not, but it doesn’t matter. That decision was already made by my genes. Having kids early or late isn’t going to make it any better or worse.

          Compare to smoking lesion.

  3. Anon says:

    Why don’t you freeze your sperm and live guilt free? In fact, this seems like good advice for most young men if it will increase the IQ of their children.

    • Scott Alexander says:

      Lack of convenient knowledge on how to go about this, plus lack of certainty that freezing sperm doesn’t damage them more than normal aging would.

      • anon says:

        At what price and level of certainty would it be worthwhile to you? I would happily pay several thousand a year for a 50% chance, for example, and expect that by the time I turn 27 this will be possible (actually I suspect it is already, but it’s not worth it for me to look into deeply until then).

        • Scott Alexander says:

          Problem isn’t uncertainty of gain per se, it’s not balancing off chance of actively making things worse.

      • Benquo says:

        Lack of convenient knowledge on how to go about this, plus lack of certainty that freezing sperm doesn’t damage them more than normal aging would.

        You also have to consider how much better you expect your information about the effects of freezing sperm to get between now and when you would want children.

        You could probably get a decent Fermi estimate for the cost and value of getting your sperm frozen in under an hour’s research time. You could calculate VOI for that hour even quicker.

      • gwern says:

        It’s easy to look up sperm freezing, and it’s a heck of a lot easier than storing eggs. My estimate was that 20 years or so of storage will run you a few thousand dollars total (it’s something like $100/$200 a year for a few vials at a cryobank); not much at all, and the real expense will be making use of the sperm…

        As for safety: remember the lower rate of birth defects with sperm donors. That implies limits on how much damage freezing could do.

  4. Anonymous says:

    “presumably” is an unnecessary disclaimer – the mutation rate has been directly measured by whole genome sequencing of parents and children.

  5. St. Rev says:

    The male reproductive system, unlike the female reproductive system, produces gametes throughout the reproductive lifetime.

    Should the second ‘reproductive’ be there?

    • David Hart says:

      Assuming you meant the third: Yes – reproductive lifetime is the period during which one is capable of reproducing, as opposed to just plain lifetime, which has an unreproductive portion at the beginning and, usually, another one at the end.

      • St. Rev says:

        Sorry, I meant third, but what I actually meant was: The second half of the sentence, as written, appears to say “the female reproductive system does not produce gametes through the reproductive lifetime”, which seems wrong.

        Human males can continue to produce gametes into old age, human females do not.

        • Scott Alexander says:

          I think I’m right as originally phrased. There’s a lot of complicated steps, but I think that the relevant part is that women form all of their egg cells while they (the woman) are still in the womb – then they just go releasing them one per month. Men form sperm throughout their reproductive lifetimes.

        • St. Rev says:

          Oh, OK! I am wrong.

  6. Johnwbh says:

    My immediate response to this as a twenty something male is that I shouldfreeze my sperm and gget a vasectomy, for the sake of my potential future children. Has anyone looked into the cost benefits of this?

    • Michael Blume says:

      I’ve looked into this a bit and the freezing part’s pretty expensive

      Also if you freeze your sperm at, say 25, and keep it until you’re 35, is there *any* science on whether the 10-years-frozen sperm is better or worse than fresh 35-year-old sperm?

      • Vaniver says:

        is there *any* science on whether the 10-years-frozen sperm is better or worse than fresh 35-year-old sperm?

        If the sperm works at all after being unfrozen (which it should), I don’t see why it would have degraded genetically. The extra mutations from being older are that your reproductive cells have (I believe) split that many dozens of times between when you were 25 and when you were 35.

        • Scott Alexander says:

          I don’t know. Anything that damages cells damages genes as well, and freezing seems potentially pretty damaging.

          I think that a lot of cloned animals turn out kind of sickly because of genetic damage incurred in the “handling” process of their gametes. There doesn’t seem to be this effect with IVF babies, so I guess that suggests there shouldn’t be with frozen sperm as well, but still not sure.

  7. Pawel Aleksander Fedorynski says:

    Shouldn’t you feel less guilty about waiting iff you would two-box on Newcomb’s problem?

  8. Ialdabaoth says:

    This all seems pretty reasonable and plausible. That said, this:

    This is sad on a general level. It suggests that guys suffering from mental disorders are unlucky in love in the same way they’re probably unlucky in a lot of other things. And it means society loses what could have been a useful piece of advice for cutting psychiatric disease.

    triggers my inner “sadistic neo-reactionary nihilist” to say “why is this sad? This is great! It guarantees an underclass that people can feel superior to, and feel no compunction against depriving and abusing.”

    I mean, seriously – have you actually considered the implications of a society in which there’s no one to do horrible things to? A society in which inflicting non-consensual suffering and shame and domination on ANYONE gets called ‘abuse’?

    • St. Rev says:

      I have vague hopes for a world where people offload their need to dominate and abuse others into MMO-PvP games. Which incidentally suggests that current efforts to reform gamer culture are really, really bad.

      • Ialdabaoth says:

        I have vague hopes for a world where people offload their need to dominate and abuse others into MMO-PvP games. Which incidentally suggests that current efforts to reform gamer culture are really, really bad.

        I dunno. Sometimes I think the Japanese had the right idea in WW2 – pick a whole segment of the population (preferably a population you’ve recently conquered), Other them, and then give them to your warrior and leader classes as playthings.

        • St. Rev says:

          I can accept that this is a thing that humans throughout history do, and that in some sense it works, but I can’t accept that it’s right.

        • Ialdabaoth says:

          I can accept that this is a thing that humans throughout history do, and that in some sense it works, but I can’t accept that it’s right.

          Can you explain the difference, in a way that a sadistic sociopath would understand and accept?

          Barring that, can you explain the difference, in a way that would cause someone who has no power to stop or mitigate abuse to suddenly gain that power?

          If you can’t do either of these, then what the hell does ‘right’/’wrong’ even matter?

        • St. Rev says:

          I use ‘right’ to mean nothing more or less than ‘I wouldn’t do that’ or ‘that makes me sad’ or perhaps ‘given the power, I would oppose this’. I didn’t mean to imply that it matters.

          What did you mean by ‘right idea’?

        • Ialdabaoth says:

          What did you mean by ‘right idea’?

          I dunno, it’s kind of an intuitive thing, but I think it boils down to a combination of “that which will most please those who are stronger than me” and “that which will most abase and alienate me from my sense of self-worth”.

          My innate sense of morality essentially boils down to “because fuck you.”

        • St. Rev says:

          So basically it’s the right idea because you find it viscerally wrong and you want to punish yourself?

        • Nick T says:

          can you explain the difference, in a way that would cause someone who has no power to stop or mitigate abuse to suddenly gain that power?

          Someone could explain the difference in a way that helps/motivates many people who individually have no power to coordinate and successfully collectively stop abuse.

      • peterdjones says:

        Notions of rightness that can’t be used to stop wrongdoing by persuasion are still useful because they can be used to justify stopping wrongdoing by force.

    • Oligopsony says:

      I think you are displaying your self-loathing here, and that also makes me sad.

    • Scott Alexander says:

      I don’t think I share the desires or intuitions that lead you to say this. I also think attributing those to the reactionaries is unfair to them.

      If there is some kind of human urge to beat up on people, I think the current method of channeling it into random strangers on the Internet is pretty good. Everyone carries a small share, and if it gets too unpleasant for people it’s easier to get away from.

      • Ialdabaoth says:

        *nod* fair enough. I suppose ‘reactionary’ is just the closest affiliation I can latch onto; my actual worldview is a weird sort of nihilistic, depersonalized, ultra-authoritarian fascism straight out of 1984, so it’s kinda hard to find people to flag tribal affiliation towards. 🙁

        • Oligopsony says:

          Come join the authoritarian left, comrade! Midcentury dystopias were designed to make us sound cool and spooky, just like “the Cathedral” is designed to make corporate diversity presentations sound cool and spooky.

        • Ialdabaoth says:

          Except for North Korea, the authoritarian left has a terrible track record.

          That said, North Korea makes up for a lot of ills. Forcing someone you don’t like to stand down-range, and then having your entire army lob artillery shells on them until they’re obliterated, has “look how huge my alpha-male cock” style written all over it, in a way that few modern regimes can compete with. (Bonus points for
          rounding up everyone related to them, down to the last toddler, and having them all summarily executed).

          … heh. I wonder if my current mood-and-mindset are more indicative of a borderline thing, or a schizoaffective thing?

        • Scott Alexander says:

          I am hard to creep out, and you are creeping me out. Please tone it down.

        • Ialdabaoth says:

          okay. sorry.

        • Error says:

          Well, I laughed at that, if it’s any consolation.

          (but it’s still Scott’s blog, and I am not a good measuring stick for sanity)

      • Konkvistador says:

        “I also think attributing those to the reactionaries is unfair to them.”

        Yup.

    • Randy M says:

      That’s a rather odd response, although I am inclined in the general direction; that is, I am sad that people suffer mental disorders; I find that allieviated slightly by the fact that this makes them less likely to pass on genes, rather than exaggerated, because this means less mental disorders, and thus, suffering, in the future.

      Of course, I wouldn’t say I am cheered that they are unlucky in love if we expand love to be platonic or simply non-reproductive. But the usage here implies Scott is using it as a euphemism for procreative love, rather than simply knowing affection.

      Making it harder to have kids is exactly what we want poorly functioning genes to do.

  9. Fnord says:

    Keep in mind that we’re talking about Denmark. I think that’s relatively unlikely to be an issue if there’s a biological explanation, but if cultural factors are relevant (divorce, spousal age difference, casual sex, etc) then the relevant culture is that of Denmark, which may not be exactly the same as the United States.

  10. Fnord says:

    Actually looking at the data, it looks a little more complicated than that. There’s also a correlation between YOUNG paternal age and most diseases. So it’s entirely possible the poverty/impulsivity effect that women are hypothesized to have is still present in men. It’s just that the other hypothesized effect is ALSO present.

    Also, not every disease responds in the same way to paternal age, and the second study looks at schizophrenia specifically. In particular, autism and other pervasive developmental disorders (unlike schizophrenia) seem to have a unidirectional correlation with age, even to the extent of reduced prevalence for teenage fathers. It’s possible that the mutational load effect is relevant there.

  11. Anthony says:

    One way to test whether the effect for men is due to less-mentally-healthy men being less desirable would be to compare the ages of the effects over time. In cohorts where the average man has his first child at 22, is the prevalence of mental illness in children of men whose first child was at 22 the same as in cohorts where the average man has his first child at 28? In Denmark, this may be problematic, as cohorts who were in their 20s or teens during the Occupation or its immediate aftermath have a Great Big Cofounder issue.

  12. Nestor says:

    Offtopic but, I was wondering if the current generation of digital natives beginning medical studies are significantly more desensitized than their forebears were? I’m no med student but from subscribing to r/WTF and seeing various ghastly things over the years on the internet I’m fairly inured, at least to the visual aspect of disease, injury and deformity.

    The guy writing Generation Kill commented that this generation of soldiers didn’t need to be desensitized to shooting humanoid figures, thanks to video games. A similar concept.

    • Scott Alexander says:

      I haven’t noticed this. I don’t remember being too creeped out by very much along the blood-and-gore line, but then, I didn’t see very much blood and gore (I haven’t done much ER, and the ER I did do was mostly free of gruesome accidents)

      Ulcers are still awful, but I don’t think video games or TV really prepare you for ulcers.

  13. dhill says:

    I was wondering why you jump to the biological conclusion right from the start, when it comes to women, but fail to do so with men. Then I read to the end and it somehow corrected. Are K-type men so forgotten today?

  14. >The children of older fathers therefore end up with a higher mutational load and more likelihood of mental disorders – not to mention a host of other issues like lower IQ, less physical ability, decreased health, et cetera. It’s very plausible and according to the Danish study the child of a 45 year old father is 1.5x more likely to develop schizophrenia and 1.8x more likely to develop autism compared to the child of a 25 year old father – not a subtle effect!

    Wat. Genetic load doesn’t work like that. If there were enough mutations in a single generation to be significantly noticeable, the species would be utterly unmaintainable without seriously strong eugenics.

    As it is, the ratio between background mutational load and the amount generated every generation is probably around 10-30 times at least. That is, we all have the equivalent of at least 10-30 generations of mutational load, with variance between people probably on the order of 5-10 generations at least, so the effect of an additional generation is probably not so significant.

    It would be good to do real calculation with real numbers, or even find some data, but I don’t buy it for now.

    That said, this is all assuming we don’t control for the genetic load of the parents. If we did control for the genetic load of the parents, we could measure the generational mutations.

  15. gwern says:

    A 538 blogger writes on this topic (interesting timing, wonder if she reads SSC?) in the post “Are Older Men’s Sperm Really Any Worse?” http://fivethirtyeight.com/features/are-older-mens-sperm-really-any-worse/ by Emily Oster:

    The researchers ran regressions where they effectively compared children born to the same father at different times in his life, and they reported enormous changes in psychiatric problems. They found big effects on autism: Children born to men over 45 were 3.5 times as likely to be diagnosed with autism as those born to men aged 20 to 24.

    …But let’s look a little more closely at the data and statistics here. The authors actually ran three analyses. First, they looked at the raw data and asked, on average, are children born to older fathers more likely to have ADHD? Second, they controlled for some demographics, such as education and income, and maternal age. And finally, they ran their “sibling fixed effects” regression. They reported their results in helpful graphs, and below we’ve replicated the one for ADHD. http://espnfivethirtyeight.files.wordpress.com/2014/04/oster-bad-sperm-adhd.png In the first analysis using raw data, older men do not appear to be more likely to have children with ADHD. In the second analysis, when the researchers’ adjusted for some characteristics of the father, mother, and so on, we see that the children of older fathers are less likely to be diagnosed with ADHD. It’s only when we move to the siblings analysis that we see a huge positive effect of paternal age on a child’s likelihood of an ADHD diagnosis.

    One theory for this gap in results is, of course, that the final analysis is the most accurate because it examines children under near ideal conditions: They were born to the same father at different times in his life. But when there is such a big difference in findings across analyses, it’s worth asking if something odd is going on. To answer this, we need to be clear on what this “sibling fixed effects” analysis really does. Consider a dad with two children, born four years apart. A basic fixed-effects model would ask whether the older child is less likely to have ADHD than the younger, and then attribute any observed difference to paternal age.

    Running this basic analysis would have the same problem with maternal age that we discussed earlier. Because mothers often age along with fathers within a family, if we analyzed sibling pairs with the same mother and the same father, it would be impossible to separate the effects of maternal and paternal age. This paper does claim to separate these effects. How? The data includes half-siblings — children who share a father but not a mother.1 The authors can infer the effects of the father’s age separately from the mother’s age by looking within groups of siblings who share a father but not a mother. That means the huge positive effect seen in the chart above essentially tells us that a later-born child of a father who has multiple kids with multiple partners is more likely to be diagnosed with ADHD. In the paper, this difference is attributed to paternal age.

    Why push so deeply into the statistics here? Seeing what the data is really saying lets us think a little more about what else might be happening. Now that we know the effects are driven by differences across half-siblings, we can start asking what else — beyond paternal age — might be driving the difference. Most obviously, we may wonder whether being a child in a fluid family situation could itself have an impact on ADHD risk (as other studies have found). Another, if more mundane, explanation for the big effect that paternal age appears to have on a child’s ADHD risk is that by striving so hard to isolate the effect of paternal age, the paper’s authors ended up studying a small number of individuals. And this makes it more likely that the results they saw were just due to chance.

    • Douglas Knight says:

      Since Oster discusses a different paper, I doubt she reads SSC. Indeed, her paper is a month newer than Scott’s first paper, that presumably prompted him. I don’t know why she claims it is from “last year.”