The role of values in the nature/nurture debate about psychiatric disorders

This paper discusses the role that values play in our estimates of the relative importance of nature/nurture factors in the etiology of psychiatric disorders. It is argued that all parameter estimates, heritability estimates, variance explained, odds ratios, and relative risks, are based, at least in part, on value judgements that are made in the course of our research activities. Four aspects of causal inference where values are particularly influential are discussed: gene/environment interactions, environmental specificity, the distinction between causes of variation and the causes of a factor, and the reification of our measures. The value component in our research is illustrated in two areas of research: life events and depression and individual factors in violence.