Chunk #110 — 5. Implications for understanding gene-brain-behavior relationships in health and disease — 5.1. Intermediate phenotypes, or “endophenotypes”
large scale linkage and association studies of alcoholism have been conducted, but the agreement across studies was very poor and, by now, there is no single well-replicated finding of a gene conferring risk for alcoholism, except the genes encoding the key enzymes of alcohol metabolism (ADHs and ALDHs), that have been known long before the GWAS era (Edenberg, 2012). However, the situation started to change in the last few years as independently replicated GWAS findings have emerged for nicotine addiction(Wang et al., 2012), schizophrenia(van Dongen and Boomsma, 2013)and other disorders, although these genetic variants account only for a very small portion of heritability of these phenotypes.
