Thursday, 17 November 2016

What's our problem with genetics?

In the field of mental health there is a distinct allergy to the question of genetic influences on cognition. At its most extreme, this allergy leads to a sort of anaphylactic reaction that has been called genetic denialism. A recent example of this (an example that prompted the epithet) is Oliver James’ book “Not in Your Genes”. However, a milder form of the allergy exists, and I call it genetic disavowalism. Genetic disavowalism is far more pervasive than genetic denialism, and finds its way into clinical psychological writing. 

Genetic Denialism has changed little in 30 years

Genetic disavowalism has valid historical roots. There are good reasons for horror when we examine the way that genetic theories have been distorted to promote policies of eugenics and even mass extermination. But as with other allergies, the responses that are mobilized against “gene talk” are out of proportion to the current level of threat. It is misguided to conclude that it is somehow desirable to steer clear of genetics, or “genetic explanations” altogether, or that the field as a whole is tainted by Nazism. As is the case with other allergies, these responses may be counterproductive, or even damaging.

When I talk about disavowalism, I am not referring to certain widely agreed upon facts about the limits of genetics in psychiatry. That is, I am not calling into question the idea that genes are only one part of the aetiological process giving rise to various mental health problems. I am not contesting that the heritability quotient is a limited form of information about the role genetic influences and leaves (for the time being) a “heritability gap” between rates of within-family concordance and accounted variance in molecular approaches to genetics. Neither am I questioning the limited practical application of genetics in many areas of psychiatry. What falls under the scope of genetic disavowalism- what I take to be intellectually unhealthy- is a detectable aversion to even considering psychiatric genetics as a reasonable field of enquiry for aetiology or therapeutics.

Genetic disavowalism can be associated with its own wrongs. I lose count of the number of times I have seen a psychologist descry genetic explanations on the grounds that they imply a person is “permanently flawed” or similar. Flawed? Let’s follow the reasoning. If a genetic explanation implies that someone is permanently flawed then presumably a theory which allows for a more transitory kind of experience (an environmentally determined, understandable “reaction”) only implies that they are temporarily flawed. The time frame changes, but the “flaw” remains. 

This is not a problem with genetics; it’s a problem with how some people (including apparently, critics of genetics) think about other people. The use of the word “flawed” is suggestive of a value judgment that has nothing to do with causes, and everything to do with how you regard a behavior or trait. If you come to the aetiological debate with the view that people with mental health problems are “flawed”, then your inclination to disavow genetics may be a defence against your own internal prejudice.

It can be helpful, in the face of genetic disavowalism, to probe intuitions about the morality of psychiatric genetic research and intervention. If genetic psychiatric research is inherently negatively morally valenced (or if it amounts to a “tedious obsession” as I have seen it said), we might ask whether it should be discontinued.

Here is a case study that bears on the question. In Steve Silberman’s Neurotribes, there is a wonderful description of the origins of our genetic understanding of Phenylketonuria (or PKU), a disorder which can result in profound cognitive and intellectual disabilities. The Norwegian researcher Ivar Følling had noticed a strong smell in the urine of a child who had developed intellectual disabilities. Further testing revealed this to be the result of high phenylpyruvic acid levels, indicative of a difficulty metabolising phenylalanine. Phenylalanine build up in the brain is what leads to the pervasive cognitive difficulties often seen in PKU. Følling showed that the underlying metabolic problem was determined by an inherited abnormality on a specific gene.

This was a serendipitous discovery that came out of a line of investigation that can easily seem hopeless; the search for genes for generalized cognitive disability. Nonetheless, its implications are extraordinary. Children with the gene can now be identified at birth and, with a simple dietary regimen, be prevented from developing the sort of pervasive cognitive difficulties that can make it impossible to live independently. Was this unexpected discovery a bad thing? Are we worryingly closes to a program of eugenics for knowing that there is a form of cognitive disability that is caused entirely by an inherited abnormality on the PAH gene? Is it morally wrong to stave off that disability by resorting to a preventative diet?

The story of PKU will not easily generalize to all areas of mental health, but it is foolish (and a form of ahistorical thinking) to suppose that unexpected shifts in our knowledge about the genetics of mental health can not now lead to other breakthroughs in treatment. In 2016, do we know all there is to know? Psychiatric genetics has been parodied by analogies to a “gene for homelessness or debt”, with the implication that it is conceptually wrong-headed to conduct genetic research in the domains of schizophrenia or depression. Maybe a gene for homelessness or schizophrenia will never be found, but genes or genetic mutations for some specific subtypes of cognitive problems are not out of the question. How to approach genetic research most fruitfully is one issue. Whether that research should take place at all is another one entirely.

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