• By Sarah Blower
  • Posted on Thursday 05th June, 2008

G x E x I x D nurtures the nature of children's development

Given the continuing advances in the science it is unsurprising that the Society of Prevention Research conference in San Francisco last week should give so much attention to gene and environment interactions and their implication for impairments to children's health and development. Centre stage was a plenary with three invited speakers, Steve Gilman, Professor of Society, Human Development, and Health at Harvard; Ken Dodge, Director of the Center for Child and Family Policy at Duke University; and Leslie Leve, senior scientist at the Oregon Social Learning Center.The context, as Gilman put it, is the shift from 'nature versus nurture' debates to 'nature and nurture'. This is generally characterized as G x E, or Gene Environment interaction. Previously scientists had talked about a diathesis-stress model in which a non-biological or genetic vulnerability or predisposition (diathesis) combined with environmental factors and life events (stressors) to produce disorders such as schizophrenia.Breakthrough research by Avshalom Caspi on the role of the MAOA enzyme in mediating the risks of child maltreatment to child well-being have brought theoretical debates into the empirical domain. But what does that mean in practice? For science the demands are going to be considerable. We now know that genes are implicated in many more aspects of children's development than currently identified and in many more ways than had been realized a decade ago. But new knowledge has also served to reveal what we do not know and still have to find out.Gilman, for example, noted that so far, out of the twenty odd thousand or so genes in the human genome, only six had been found to play an important role in the kinds of impairments and disorders that generally interest prevention scientists. None of these genes have a decisive effect; they play their part through the environment. And as with environmental stressors, a risky genotype sometimes has a negative effect on child outcomes, but not always. For Gilman the need was to add to the G x E equation the I for Individual and D for the child's stage of development.Ken Dodge sought to stand some of the orthodox arguments on their head. Too often, he complained, environment is viewed as the context altering in some way the genetic influences. A more likely scenario is that genes alter our susceptibility to environmental risks.Leve's take home message from the challenges of the new genetics is that we have to get a whole lot smarter about measuring the environment. It turns out that the G part of the equation is pretty complicated. But all geneticists understand MAOA in the same way. This cannot be said of social scientists comprehension of the environment. There are a myriad of perspectives on low warmth parenting and on the toxicity of school or community ethos, both of which are environmental factors that might mediate or moderate the role of MAOA.But for most people in the audience the question was 'so what?' How does this help with intervention?The answer is far from clear. Steve Gilman said that G x E was 'a seductive idea that has so far told us nothing about intervention.' Ken Dodge was more optimistic. 'For the first time in my life time I can envisage a world where we will be able to respond effectively to childhood disorders' he told the San Francisco audience. Leslie Leve gave several examples of how G x E research might explain how particular aspects of the environment may raise the value of prevention efforts for some dimensions of children's development but not others.The most promising line of enquiry may be to alter the circumstances of people with a 'bad fit' between their genes and environment. Ken Dodge, speaking from personal experience, pointed out how certain environments helped children with dyslexia to blossom but drove others into a spiral of despair.Despite the huge impact the understanding of genes is having on prevention science, all of the implications for practice concern making changes to the environment.As well as huge challenges and opportunities for the prevention world, the G x E debates also pose threats. It was the most optimistic of the speakers Ken Dodge who reminded the audience that genetic information could be used by employers or insurance companies or health providers to the disadvantage of individuals. The new G in town is GINA, the Genetic Information Non-Discrimination Act that is currently getting a good airing before federal lawmakers.References Caspi A, McClay J, Moffitt T, Mill J, Martin J, Craig I, Taylor A, Poulton R, (2002) “Role of Genotype in the Cycle of Violence in Maltreated Children”, Science , 297, (5582), pp851-854Caspi A, Sugden K, Moffitt T, Taylor A, Craig I, Harrington H, McClay J, Mill J, Martin J, Braithwaite A, Poulton R, (2003) "Influence of Life Stress on Depression: Moderation by a Polymorphism in the 5-HTT Gene”, Science , 301, (5631), pp386-389

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