to have shared genetic underpinnings (e.g. Schizophrenia and Bipolar Disorder, Bipolar and Major Depressive Disorder) [International Schizophrenia Consortium et al., 2009; Liu et al., 2011]. The existing literature suggests that phenotype harmonization may reveal novel loci for disease subtypes as well as shared variants among broad categories of disease. These examples illustrate how phenotype harmonization is a crucial first step and a key component of successful multi-study collaboration, where investigators are faced with the challenge of harmonizing previously collected phenotype data derived from diverse data collection instruments over different timeframes and in varying degrees of detail.
