The right loves genetic explanations for poverty or mental illness. But science fingers society.

When the map of the human genome was presented to the world in 2001,
psychiatrists had high hopes for it. Itemising all our genes would
surely provide molecular evidence that the main cause of mental illness
was genetic – something psychiatrists had long believed. Drug companies
were wetting their lips at the prospect of massive profits from unique
potions for every idiosyncrasy.

But a decade later, unnoticed by
the media, the human genome project has not delivered what the
psychiatrists hoped: we now know that genes play little part in why one
sibling, social class or ethnic group is more likely to suffer mental
health problems than another.

This result had been predicted by
Craig Venter, one of the key researchers on the project. When the map
was published, he said that because we only have about 25,000 genes
psychological differences could not be much determined by them. "Our environments are critical,"
he concluded. And, after only a few years of extensive genome
searching, even the most convinced geneticists began to publicly admit
that there are no individual genes for the vast majority of mental
health problems. In 2009 Professor Robert Plomin, a leading behavioural
geneticist, wrote that the evidence had proved that "genetic effects are much smaller than previously considered: the largest effects account for only 1% of quantitative traits".
However, he believed that all was not lost. Complex combinations of
genes might hold the key. So far, this has not been shown, nor is it
likely to be.

This February's editorial of the Journal of Child
Psychology and Psychiatry was entitled "It's the environment, stupid!".
The author, Edmund Sonuga-Barke, stated that "serious science is now
more than ever focused on the power of the environment … all but the
most dogged of genetic determinists have revised their view".

In
Sonuga-Barke's own field, attention deficit hyperactivity disorder, he
observed that "even the most comprehensive genome-wide scans available,
with thousands of patients using hundreds of thousands of genetic
markers … appear to account for a relatively small proportion of
disorder expression". Genes hardly explained at all why some children
have ADHD and not others.

That was illustrated recently in a heavily publicised study
by Anita Thapar, of Cardiff University. Although she claimed to have
proved that ADHD is a "genetic disease", if anything, she proved the
opposite. Only 16% of the children with ADHD in her study had the
pattern of genes that she claimed causes the illness. Taken at face
value, her study proved that non-genetic factors cause it in 8 out of 10
children.

Another theory was that genes create vulnerabilities.
For example, it was thought that people with a particular gene variant
were more likely to become depressed if they were maltreated as
children. This also now looks unlikely. An analysis of 14,250 people
showed that those with the variant were not at greater risk of
depression. Nor were they more likely to be depressed when the variant
was combined with childhood maltreatment.

In developed nations,
women and those on a low income are twice as likely to be depressed as
men and the wealthy. When DNA is tested in large samples, neither women
nor the poor are more likely to have the variant. Worldwide, depression
is least common in south-east Asia. Yet a study of 29 nations found the
variant to be commonest there – the degree to which a society is
collectivist rather than individualistic partly explains depression
rates, not genes.

Politics may be the reason why the media has so
far failed to report the small role of genes. The political right
believes that genes largely explain why the poor are poor, as well as
twice as likely as the rich to be mentally ill. To them, the poor are
genetic mud, sinking to the bottom of the genetic pool.

Writing in 2000, the political scientist Charles Murray made a rash prediction he may now regret. "The story of human nature, as revealed by genetics and neuroscience, will be conservative in its political [shape]."
The American poor would turn out to have significantly different genes
to the affluent: "This is not unimaginable. It is almost certainly
true." Almost certainly false, more like.

Instead, the Human
Genome Project is rapidly providing a scientific basis for the political
left. Childhood maltreatment, economic inequality and excessive
materialism seem the main determinants of mental illness.
State-sponsored interventions, like reduced inequality, are the most
likely solutions.

 

Source: The Guardian – http://goo.gl/3vvx