ABSTRACT
Introduction............................................................................................................ 227 16.1 Bipolar Disorders ......................................................................................... 228
16.1.1 Genetic Epidemiology: Family Studies........................................... 228 16.1.2 Genetic Epidemiology: Twin Studies .............................................. 228 16.1.3 Molecular Linkage Studies .............................................................. 230 16.1.4 Linkage Disequilibrium Studies ...................................................... 231
16.2 Recurrent Unipolar Disorders...................................................................... 236 16.2.1 Genetic Epidemiology: Family Studies........................................... 236 16.2.2 Genetic Epidemiology: Twin Studies .............................................. 237 16.2.3 Molecular Linkage Studies .............................................................. 237
Summary ................................................................................................................ 237 References.............................................................................................................. 238
This chapter reviews some aspects of the genetic epidemiology and molecular genetic research on bipolar disorders (BDs) and recurrent unipolar disorders (RUPs). Genetic concepts of linkage and linkage disequilibrium (LD) are reviewed. Given that the inherited susceptibilities for BD and RUP are explained by multiple genes of small effect, simulations indicate that universal confirmation of vulnerability genes cannot be expected due to power issues, sampling variation, and genetic heterogeneity. With this background, several valid linkages of BD to genomic regions are reviewed, including some that may be shared with schizophrenia. These results suggest that nosology must be changed to reflect the genetic origins of the multiple disorders that are collectively described by the term BD. The briefer history of RUP molecular linkage and LD studies is also reviewed.
