Genetic Research in Psychiatry: A Brief Update


As expected, we have seen several new gene discovery claims in psychiatry during the past 12 months, which like previous such claims put forward since the 1960s, are unlikely to be replicated. I might examine one or more of the studies these claims are based upon in future posts.

It has been over a year since my last post, as I have been working on a new book whose hardcover edition is scheduled to be published next month by Routledge. The title is The Trouble with Twin Studies: A Reassessment of Twin Research in the Social and Behavioral Sciences.  For more information, please see the page and the Taylor & Francis page. The book approaches twin research in the social and behavioral sciences from a critical perspective, with a special emphasis on so-called studies of “reared-apart” twins. The most famous investigation of this type is the Minnesota Study of Twins Reared Apart, whose major problem areas are covered in depth in Chapters 5 and 6, and may be the subject of a future MIA post. Although I have examined various aspects of twin research in two previous books, in the new book I look at the major issues much more closely, with a fresh perspective based on the very latest research findings.

While reared-apart twin studies have focused on psychological characteristics such as IQ and personality, the mainstay of psychiatric genetic research, and the basis of genetic theories and claims in psychiatry, have been “twin method” studies which compare the behavioral resemblance of reared-together identical versus reared-together same-sex fraternal twin pairs (see my March 13th, 2013 MIA post). I devote two chapters to the fallacy of the twin method and its clearly false underlying assumption that identical and fraternal twins grow up experiencing similar behavior-shaping environments (the “equal environment assumption”).

Although supporters of psychiatric genetic twin studies argue that the equal environment assumption has been tested and upheld, almost everyone (twin researchers and their critics alike) agrees that reared-together identical pairs grow up experiencing much more similar environments than experienced by same-sex reared-together fraternal pairs. Almost everyone also agrees that identical pairs resemble each other more than fraternal pairs for most psychiatric disorders. Therefore, although completely overlooked by psychiatry and psychiatric genetics, the best-replicated disconfirmation of the validity of the twin method’s equal environment assumption consists merely of all the psychiatric twin studies ever performed. Nine decades of such studies have shown, with almost complete uniformity, that pairs experiencing similar environments and high levels of identity confusion and attachment — identicals — resemble each other more for psychiatric disorders than do pairs experiencing less similar environments and much lower levels of identity confusion and attachment — fraternals.

In addition to twin research, in the Trouble with Twin Studies chapter on twin research in psychiatry I examine mainstream psychiatry’s position that psychiatric disorders are valid medical conditions that can be reliably diagnosed. I argue that the current (scientifically unsupported) emphasis on brain disorders and genetics in psychiatry causes the field to overlook or de-emphasize many environmental factors that have been shown to play an important role in causing emotional distress and dysfunction.

Ironically, if molecular genetic research had actually delivered the genes for psychiatric disorders promised by mainstream psychiatry and its subfield of psychiatric genetics, twin research today would be largely obsolete because focus would have shifted to molecular genetic research, and a person’s genotype and diagnosis would be determined directly from his or her DNA. Twin research, therefore, retains its current level of importance in psychiatry only because the genes believed to exist for its disorders, based largely on genetic interpretations of twin studies, have not been found.

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  1. Thanks, Jay, and very timely. Just last Friday, one of my minor clients explained her symptoms through the lens of genetic and chemical abnormalities. I asked whether she’d be interested in different views and lent her a copy of your earlier book, Gene Illusion, and Valenstein’s book. Thanks for fighting the good fight.

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  2. I just noticed this attempt to write speculation into science when I read the DSM-V definition of mental illness. I was really surprised that they are now openly aligning themselves with psychobiology regardless of lacking evidence. I a lso read an article about psychiatry, genetics, and the law as though the author felt that genetics should be permissible as evidence that a person was more apt to have committed a crime.

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  3. What do you think about this study: “Schizophrenia not a single disease but multiple genetically distinct disorders” ( You can find a description and critique in PubMed, too ( It says that Schizophrenia is composed of 8 distinct heritable diseases, and that this diseases are determined by genetic clusters with risks up to 100 percent. Among the authors is the well-known C. Robert Cloninger. They used data-mining and machine-learning methods to process the data. It’s hard for me to believe this, but I’m not an expert. What do you say, Jay.

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  4. Thank you for another articulate post challenging the pseudoscience of behavioral genetics!

    My biggest criticism of the equal environment assumption is that it ignores how twins are part of their own environment- that twins have a cultural bias that is typically stronger than researchers. In reality, identical twins predominately expect their behavior and mental health to be similar while fraternal twins expect their behavior and mental health to be different. Research never compensates for this bias.

    Looking forward to your new book, Steve

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    • Thanks, Steve.

      You make some interesting points about twins, and researchers do tend to overlook many obviously problematic aspects of twin research. I think you will like my upcoming book, where I cover many of the central concepts and methods of behavioral genetics from a critical perspective.


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    “Schizophrenia is a disorder which although many genetic risk factors have been identified, no effective treatment is available. ” – This statement is a LIE.

    I was diagnosed as acutely Schizophrenic in 1980, chronically Schizophrenic in 1983, and Schizo affective in 1984, at Galway (University Hospital) Ireland.

    I stopped strong medication in April 1984 and made complete recovery with the help of basic psychotherapy. I have been well for 30 years. This study is irrelevant.

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  6. I’m reminded that last week Medicare announced that it would pay for Assurex’s Genesight test for people with depression. Assurex claims that it measures and analyzes important genomic variants affecting the metabolism and response to behavioral health medications in individual patients.

    While my peers and I suffering from depression might never expect to receive the oft cited non-medication therapies which promote recovery at our community mental health centers we can easily get antidepressants, antipsychotics adjunctively and now genetic tests at little or no cost. So lets see CBT, nah. DBT, simply not available. Mindfulness, what? Genesight’s test, easy despite it costing between $2000 and $2500. I’ve been told by the community mental health center that all I need do is make an appointment.

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  7. I think the last paragraph of this article is the most telling. We are still stuck with “it’s a heritable disease” because of some meaningless correlations but if it were the case with current genomic and transcriptomic studies we should have at least some answers. Instead we have huge lists of genes which are marginally associated with this or that “psychiatric disorder”. Even if some genes (like those making sure we do not develop into psychopaths) are necessary for the development of “mental illness” (or its underlying cause – being able to experience emotions) none of them is sufficient.

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