Maximizing power remains a key issue for molecular genetic studies, even with the endophenotype approach. Twin studies can increase power in endophenotype association studies (or GWAS) by decreasing the number of phenotypes to be tested for molecular genetic associations. This decrease may be achieved in three main ways. First, they may help determine which measurements may be dropped; second, they may determine which measurements may be combined; and third, they can help determine which measurements are most likely to have the power to result in successful gene-hunting.
