Do susceptibility loci contribute to the expression of more than one mental disorder? A view from the genetics of Alzheimer's disease

The susceptibility of developing most major psychiatric disorders is determ ined in part by contributions from risk alleles at multiple genetic loci. T he central aim of this article is to highlight evidence from studies of neu rodegenerative disorders suggesting that some of these alleles are shared b y more than one psychiatric disorder, and to explore mechanisms that may un derly these pleiotropic effects. The identification of constellations of su sceptibility alleles associated with particular mental disorders will provi de opportunities for new insights into the molecular and cellular pathophys iology of these disorders, and will have a major impact on psychiatric rese arch and clinical care, This approach to reducing the variance in etiopatho genesis is also likely to be important for achieving the optimal use of ava ilable treatments (maximizing effectiveness and minimizing side effects), a nd for the discovery of novel medications or other interventions.