that classical statistical methods for ideal population data, which consist of independent individuals, may not be applicable: an important feature of population isolates is that the relatedness of two random individuals may be non-negligible [Bourgain and Genin, 2005]. Such cryptic relatedness may also be found in outbred populations as a source of population structure, and cryptic relatedness among affected individuals might be another serious source of spurious positive results [Devlin and Roeder, 1999; Bacanu et al., 2000] because cases share a genetic disorder [Bourgain and Genin, 2005; Voight and Pritchard, 2005].
