Sun, Oct 16, 2005 - Page 19 News List

Genes play a role in cases of depression

New evidence links inequality and social status to the probability of suffering depression

By Oliver James  /  THE GUARDIAN , LONDON

The chemicals that are sloshing round your brain at any one moment profoundly affect how you feel or behave. Low levels of serotonin (the

neurotransmitter influenced by antidepressants such as Prozac) are associated with depression, and high ones with violence. Levels are sensitive to one's social status, which may be why both problems are more common among poor people (yet another reason to create equal societies -- see Love, Empowerment and Social Justice by Tim Root and The Impact of Inequality by Richard Wilkinson). But hard evidence is now emerging that genes may play a part.

A recent study found that people with certain genetic variants are more likely to have low serotonin -- but only if they were stressed. Poor people with the variant were at greater risk of low serotonin, but not rich ones, suggesting that the stress of being strapped for cash fulfils that genetic potentiality. Interestingly, overall, the poor were no more likely to have the genetic variant than the rich, giving the lie to the idea that the poor have dodgy genes -- a kind of genetic sludge at the bottom of the gene and

social-class pool.

The plot thickens when you take the impact of child-rearing into account. In a series of studies in New Zealand, adult depression, violence and heavy cannabis use were shown to be about twice as likely if the dodgy genetic variant was combined with maltreatment as a child. Conversely (and very surprisingly to me), if you had variant-free genes, severe maltreatment did not increase your

likelihood of problems.

This finding was recently replicated, in some respects, suggesting there is something to it. However, there remains a major reason for

scepticism. If genes are so important when combined with adverse environments, why are there huge

fluctuations in the prevalence of most emotional problems, like depression and violence? Since it takes millennia for genetic change to occur in a population, genes could not be the cause of these variations. In Britain, violence against the person has increased

45-fold since 1950.

Equally, there can be dramatic drops in the amount of violence that can have nothing to do with genes: rates of homicide in America have almost halved since 1993.

`Bit of both', nature-nurture exponents would argue that it just goes to show that dodgy genes only get expressed if environments activate them. But that could not explain such huge changes. Far more probable is that genetic vulnerability explains none of a 45-fold change in such a short period -- that an awful lot of people with no genetic susceptibility are made, rather than born, violent or non-violent, depending on their society.

Even if it emerges that genes are always involved to some degree, one of the most striking implications of such studies is that emotionally benign

environments are crucial: if you want the minimum of depression or violence, they make an overwhelming case for having a minimum of poor people and abusive parents, rather than societies making tiny minorities super-rich.

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