Writing Amish culture into genes: biological reductionism in a study of manic depression.

Critical realism is used to explore the problem of reductionism in a classic (the Amish Study) and widely-cited study of manic depression. Along with related ideas drawn from the works of R.C. Lewontin, Arthur Kleinman, and Byron Good, it is shown that natural and social scientists deploy atomistic and holistic reductionism; this, in turn, leads to the construction of artificially 'closed systems' through the control of variables or exogenous forces. The psychiatric genetic studies of the Amish were predicated on the assumption that Amish society is homogeneous and unchanging and, therefore, closed. We conclude by arguing that interactions between behaviors and genes, where they exist, take place only within open systems, characterized by multiple mechanisms-social and biological-that together co-determine any event. To move forward, it is argued, behavior and gene research requires recognition and resolution of the philosophical conundrums that accompany reductionism.