Headlines on the purported genetic basis for mental illness - like this one from The Washington Post: "Some children born with the genetic risk for schizophrenia, scientists say" - have been staples of scientific journalism for years now. But what do they really mean?
Is mental illness really just a matter of bad luck in the genetic lottery?
Let's focus on schizophrenia, as this condition generally is considered among the most severe and intractable mental illnesses, and the one most likely to have a biological or genetic basis. If the case for genetic determinism fails here, it is probably even weaker elsewhere.
The case of the "22q11.2 deletion syndrome" is instructive. This is the deletion of a tiny part of chromosome 22, some 30 to 50 different genes, correlated with a whole host of physical abnormalities and somatic illnesses. In addition, about 20% of individuals with this mutation become schizophrenic, as opposed to about 1% of the general population.
But that means the majority of people with this mutation never become schizophrenic. And this mutation is, fortunately, uncommon. The 22q deletion and a handful of even rarer structural variants with even smaller effect sizes account for less than 2%% of total cases of schizophrenia.
Scientists have known about this mutation since 1981. Since then, the new technique of genome-wide association studies has enabled them to go over the human genome with a fine-toothed comb. And what have they found?
They certainly have not found any genetic variants with anywhere near the effect size of the 22q deletion. All the ones they have found have a far weaker correlation with schizophrenia - on the order of a one in 500 increase in absolute risk or less. In aggregate, all these genes account for only a small proportion of the risk for schizophrenia.
If there are more such genes out there waiting to be discovered, their correlation with schizophrenia most likely is weaker still. These are not disease genes, as genes for Tay-Sachs disease or cystic fibrosis are. Rather, they are a part of the normal range of human genetic variation.
Our genes are not our destiny. There is no such thing as a gene that makes it impossible not to be schizophrenic.
So, what is the cause of schizophrenia and other mental illnesses? There is evidence that these conditions correlate with physical, sexual and emotional abuse, along with other categories of adverse childhood experience. This correlation is robust, reliable and dose-dependent. It cuts across national boundaries, income brackets and ethnic identities. It has been verified again and again in prospective cohort studies; population-based, cross-sectional studies; and case-control studies.
Instead of inquiring of the mentally ill "What's wrong with those people?" perhaps we should be asking them directly "Who did what to you?"
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All that genetic researchers have added to our understanding is that individuals vary in their susceptibility to trauma - and that a small part of that variation is heritable. That's not very surprising. Probably anyone with experience of life as it is lived could have guessed as much.
It's not clear where this research is supposed to lead. If a child is being abused, do we stop the abuse, or do we give her a blood test? And if the test indicates that she is at low risk for schizophrenia, do we leave her in the abusive situation?
There are dozens - perhaps hundreds - of mutations that are (weakly) correlated with schizophrenia, and most of these are rare, which enormously complicates the task of using genetic research to find a pharmacological cure for this condition. So-called "antipsychotic" medications may tranquilize these patients in the short term, but there is overwhelming evidence that their long-term use leads to worse outcomes than if they had never been used.
Where do we go from here? The fact that schizophrenia and other mental illnesses have their roots in personal and social factors suggests that they might best be treated on a personal and social level.
Indeed, the Open Dialogue Therapy pioneered by Jaako Seikkula and his colleagues in Finnish Western Lapland has shown great promise in ameliorating these conditions. Dr. Seikkula told me that this treatment has caused the incidence of first-time episodes of schizophrenia in that part of the world to decline by an astonishing 90%, most likely because this prompt and thorough intervention leads to an early amelioration of psychotic symptoms, which must persist for six months before a diagnosis of schizophrenia can be rendered.
When I asked Dr. Seikkula if Open Dialogue Therapy is a cure for schizophrenia, his answer was short and straight to the point: Yes.
Why isn't this front-page headline news?
ABOUT THE WRITER
Patrick D. Hahn is the author of "Madness and Genetics Determinism: Is Mental Illness in Our Genes?" (Palgrave Macmillan, 2019). He can be reached at firstname.lastname@example.org.
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