Furthermore, heritability estimates obtained using family data showed a good convergence with the results of twin studies. In one study, relative EEG power data obtained from 298 members of 45 families were subjected to principal component analysis. The alpha-power factor accounting for 38% of the total variance showed highly significant parent-offspring (r=.38) and sibling (r=.41) correlations, suggesting about 0% heritability (Anokhin, 1989). This convergence suggests that correlations between first-degree relatives obtained in family studies represent genetic transmission, rather than similarity arising from sharing the same environmental factors. A study of non-twin siblings has shown somewhat lower heritabilities of the resting EEG power assessed using both monopolar and digitally constructed bipolar derivations(Tang et al., 2007). Lower heritability estimates in the latter study can be explained by a very broad age range of 7 to 70 years which may lead to additional non-familial variance that is difficult to account for statistically. Both family (Anokhin, 1989) and twin (Zietsch et al., 2007) studies employing multivariate genetic analysis of absolute power measures of EEG frequency bands point to high phenotypic and genetic correlations among
