Sir

Your News Feature ‘The brains of the family’ (Nature 454, 154–157; 2008) and accompanying Editorial ‘An unnecessary battle’ (Nature 454, 137–138; 2008) highlight the need to adopt a more integrated perspective when trying to unravel the biological complexity of neuropsychiatric disorders such as schizophrenia and depression. But the ‘battle’ between genetics and neuroscience, despite being well funded, may be missing the point.

Napoleon Bonaparte advised: “Never interrupt your enemy when he is making a mistake.” Those of us who assess the contribution of non-heritable risk factors to neuropsychiatric illness would like to politely interrupt this battle to remind opponents that environmental risk factors have now overtaken genetic factors with respect to both effect size and the proportion of the population that is affected.

For schizophrenia, for example, factors relating to urban birth, cannabis use and migrant status are well replicated and have relatively large effects — in contrast to the scant evidence that remains after decades of genetics research. Although the 'heritability index' for schizophrenia is large (about 85%), this metric encompasses the neglected contribution of gene–environment interactions, as well as the high-profile genetic component. This key point is largely forgotten in the heat of the battle.

It has been convincingly argued (A. Caspi and T. E. Moffitt Nature Rev. Neurosci. 7, 583–590; 2006) that the power to detect genuine genetic-susceptibility loci would be substantially increased if we could stratify samples according to environmental risk factors. Let's have more funding to help fine-map the wide range of non-heritable risk factors associated with disabling disorders such as schizophrenia and depression, and discover how they act. These clues are too valuable to overlook.

See also: Mental health: maybe human troubles don't fit into set categories Mental health: drop ideological baggage in favour of best tools