The Fisher z-score analysis confirmed that MZ twins showed considerably higher correlations for OCS than DZ twins (children/adolescents: Diff Z = 0.30, 95% CI 0.17–0.42, p < 0.01; adults: Diff Z = 0.26, 95% CI 0.21–0.31, p < 0.01; total: Diff Z = 0.28, 95% CI 0.21–0.34, p < 0.01) (Fig. 7). Based on the tetrachoric correlations, we estimated that A = 0.46, C = 0, and E = 0.54 for the total sample; A = 0.50, C = 0, E = 0.50 for children/adolescents; and A = 0.45, C = 0, and E = 0.55 for adults.
