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https://news.ycombinator.com/item?id=33624032 https://news.ycombinator.com/item?id=33624032 > (8) Family genetic studies. The phrase “family genetic studies” i

https://news.ycombinator.com/item?id=33624032 https://news.ycombinator.com/item?id=33624032 > (8) Family genetic studies. The phrase “family genetic studies” is commonly used in psychiatry to refer to designs in which investigators examine the familial aggregation of one or more disorders, such as panic disorder or major depression, within intact (i.e., non-adoptive) families (e.g., Weissman, 1993). Given that the familial aggregation of one or more disorders within intact families could be due to shared environment rather than—or in addition to—shared genes (Smoller and Finn, 2003), the phrase “family genetic study” is misleading. This term implies erroneously that familial clustering of a disorder is necessarily more likely to be genetic than environmental. It may also imply incorrectly (Kendler and Neale, 2009) that studies of intact families permit investigators to disentangle the effects of shared genes from shared environment. Twin or adoption studies are necessary to accomplish this goal. > (9) Genetically determined Few if any psychological capacities are genetically “determined”; at most, they are genetically influenced. Even schizophrenia, which is among the most heritable of all mental disorders, appears to have a heritability of between 70 and 90% as estimated by twin designs (Mulle, 2012), leaving room for still undetermined environmental influences. Moreover, data strongly suggest that schizophrenia and most other major mental disorders are highly polygenic. In addition, the heritability of most adult personality traits, such as neuroticism and extraversion, appears to be between 30 and 60% (Kandler, 2012). This finding again points to a potent role for environmental influences.

cactusplant7374 4y ago
> There's little solid evidence for inherited mental illness > Even schizophrenia, which is among the most heritable of all mental disorders, appears to have a heritability of between 70 and 90% as estimated by twin designs (Mulle, 2012), leaving room for still undetermined environmental influences. You have set the bar high.
- svnt 4y ago
  You can think of those percentages less like “there is only 10-30% left to explain” and more like “we can explain most of it we think but we have no idea how these complex factors interact” They basically look at fraternal and identical twins and assume (because their environments are otherwise probably close) that any differences in outcome are heritable. It’s a huge leap of faith.
  - barry-cotter 4y ago
    > They basically look at fraternal and identical twins and assume (because their environments are otherwise probably close) that any differences in outcome are heritable. It’s a huge leap of faith. You’re making it sound like the researchers are idiots who have never thought about how their tools might not be measuring what they hope they are. As well as identical/fraternal twins you can also look at other sorts of relatedness, e.g. half siblings are on average as related as first cousins and on average you’re as closely related to each parent as each full sibling. Psychological traits are inherited like height is, not like language is[1]. Mental illness is highly heritable though the expression varies[2]. As a parallel line of evidence to confirm classical twin studies and those based on degrees of shared ancestry cheap genetic testing has allowed testing how closely people are related. So you don’t have to assume a sibling shares 50% of their genes. You can see if they’re 73% similar or 41%. Or you can take people who have no known shared recent ancestry and see how similar they are on the trait of interest. To the best of my knowledge behaviour genetics is holding up. For psychological traits genetics is more powerful than developmental noise. [1]> Genetic Influence on Human Psychological Traits > There is now a large body of evidence that supports the conclusion that individual differences in most, if not all, reliably measured psychological traits, normal and abnormal, are substantively influenced by genetic factors. This fact has important implications for research and theory building in psychology, as evidence of genetic influence unleashes a cascade of questions regarding the sources of variance in such traits. A brief list of those questions is provided, and representative findings regarding genetic and environmental influences are presented for the domains of personality, intelligence, psycho- logical interests, psychiatric illnesses, and social attitudes. These findings are consistent with those reported for the traits of other species and for many human physical traits, suggesting that they may represent a general biological phenomenon. https://utahpolicy.com/wp-content/uploads/2013/12/bouchard.04.curdir.pdf https://utahpolicy.com/wp-content/uploads/2013/12/bouchard.0... [2]> The p factor: genetic analyses support a general dimension of psychopathology in childhood and adolescence > Diverse forms of psychopathology generally load on a common p factor, which is highly heritable. There are substantial genetic influences on the stability of p across childhood. Our analyses indicate genetic overlap between general risk for psychiatric disorders in adulthood and p in childhood, even as young as age 7. https://acamh.onlinelibrary.wiley.com/doi/pdfdirect/10.1111/jcpp.13113 https://acamh.onlinelibrary.wiley.com/doi/pdfdirect/10.1111/...

cactusplant7374 4y ago

> There's little solid evidence for inherited mental illness > Even schizophrenia, which is among the most heritable of all mental disorders, appears to have a heritability of between 70 and 90% as estimated by twin designs (Mulle, 2012), leaving room for still undetermined environmental influences. You have set the bar high.

svnt 4y ago
You can think of those percentages less like “there is only 10-30% left to explain” and more like “we can explain most of it we think but we have no idea how these complex factors interact” They basically look at fraternal and identical twins and assume (because their environments are otherwise probably close) that any differences in outcome are heritable. It’s a huge leap of faith.
- barry-cotter 4y ago
  > They basically look at fraternal and identical twins and assume (because their environments are otherwise probably close) that any differences in outcome are heritable. It’s a huge leap of faith. You’re making it sound like the researchers are idiots who have never thought about how their tools might not be measuring what they hope they are. As well as identical/fraternal twins you can also look at other sorts of relatedness, e.g. half siblings are on average as related as first cousins and on average you’re as closely related to each parent as each full sibling. Psychological traits are inherited like height is, not like language is[1]. Mental illness is highly heritable though the expression varies[2]. As a parallel line of evidence to confirm classical twin studies and those based on degrees of shared ancestry cheap genetic testing has allowed testing how closely people are related. So you don’t have to assume a sibling shares 50% of their genes. You can see if they’re 73% similar or 41%. Or you can take people who have no known shared recent ancestry and see how similar they are on the trait of interest. To the best of my knowledge behaviour genetics is holding up. For psychological traits genetics is more powerful than developmental noise. [1]> Genetic Influence on Human Psychological Traits > There is now a large body of evidence that supports the conclusion that individual differences in most, if not all, reliably measured psychological traits, normal and abnormal, are substantively influenced by genetic factors. This fact has important implications for research and theory building in psychology, as evidence of genetic influence unleashes a cascade of questions regarding the sources of variance in such traits. A brief list of those questions is provided, and representative findings regarding genetic and environmental influences are presented for the domains of personality, intelligence, psycho- logical interests, psychiatric illnesses, and social attitudes. These findings are consistent with those reported for the traits of other species and for many human physical traits, suggesting that they may represent a general biological phenomenon. https://utahpolicy.com/wp-content/uploads/2013/12/bouchard.04.curdir.pdf https://utahpolicy.com/wp-content/uploads/2013/12/bouchard.0... [2]> The p factor: genetic analyses support a general dimension of psychopathology in childhood and adolescence > Diverse forms of psychopathology generally load on a common p factor, which is highly heritable. There are substantial genetic influences on the stability of p across childhood. Our analyses indicate genetic overlap between general risk for psychiatric disorders in adulthood and p in childhood, even as young as age 7. https://acamh.onlinelibrary.wiley.com/doi/pdfdirect/10.1111/jcpp.13113 https://acamh.onlinelibrary.wiley.com/doi/pdfdirect/10.1111/...