Amish revisited: next-generation sequencing studies of psychiatric disorders among the Plain people

The rapid development of next-generation sequencing (NGS) technology has led to renewed interest in the potential contribution of rarer forms of genetic variation to complex non-mendelian phenotypes such as psychiatric illnesses. Although challenging, family-based studies offer some advantages, especially in communities with large families and a limited number of founders. Here we revisit family-based studies of mental illnesses in traditional Amish and Mennonite communities – known collectively as the Plain people. We discuss the new opportunities for NGS in these populations, with particular emphasis on investigating psychiatric disorders. We also address some of the challenges facing NGS-based studies of complex phenotypes in founder populations.