0.01). The use of the standard error of the tetrachoric correlation did not generate significant changes in the above results.Table 2OCD twin studies.Author/yearCountryInclusion age criteriaTwin pairsAssessment toolsTwin correlations by zigozityVariance component estimates based on ACE model coefficient, 95% CIMZ nDZ nMZMZMMZFDZDZMDZFDOSAdditive genetic (A2)Shared environment (C2)Non-shared environment (E2)Clifford et al. [30]UKAdult250p198pLOI–0.500.44–0.220.130.11–––Jonnal et al. [31]van Grootheest et al. [70]USA*Virginia Twin RegistryAdult331p193pPADUA0.34 (C)0.28 (O)––0.14 (C)0.06 (O)–––0.360.00.64Eley et al. [33]UK*Twins Early Development Study (TEDS)Children (4 y)23596046OCB (not standardized instrument)0.590.580.190.280.260.65 (0.61–0.69)0.37 (0.31–0.39)Hudziak et al. [34]Netherlands* Netherlands Twin Registry (NTR)Children7 y1582p10 y1099p12 y607p26641742955CBCL-OCS–––0.550.590.570.570.540.50–––0.310.350.300.210.220.400.300.330.330.560.550.360.00.00.160.560.550.36Bolton et al. [35]Bolton et al. [55]UK*TEDSChildren (6 y)1599p3063pADIS-C/P0.57 (0.24–0.80)0.67 (0.22–0.92)––0.22 (−0.22–0.43)0.38 (0.07–0.64)–––0.29 (0.00–0.68)0.55 (0.08–0.89)0.18 (0.00–0.48)0.11 (0.00–0.38)0.53 (0.28–0.80)0.34 (0.09–0.65)van Grootheest et al. [56]Netherlands*NTRAdolescents and adult15847662YARS-OCS–0.440.50–0.130.260.21–––van Grootheest et al. [32]Netherlands*NTRAdolescents12 y60414 y71216 y69684810881118YARS-OCS, PADUA ABBR–––0.500.570.450.450.600.58–––0.380.170.300.360.300.330.210.220.220.270.570.540.180.000.000.540.430.46Hur and Jeong [37];Hur [36]Korea*South Korean Twin Registry (SKTR)Juvenile (13–24 y)524p228pMOCI0.56 (0.45–0.65)0.39 (0.30–0.48)0.24 (−0.1–0.46)0.36 (0.14–0.56)0.38 (0.20–0.53)0.69 (0.64–0.73)–0.73 (0.69–0.77)Tambs et al. [38]Norway*Norwegian Institute of Public Health Twin Panel (NIPHTP)Adults (28 y)665p720pCIDI–0.450.35–0.200.32–0.36 (0–0.65)0.31 (0–0.49)0.70 (0.59–0.80)van Grootheest et al. [39]Netherlands*NTRAdults18 y653p20 y694p26 y336p33 y867p984934709775YARS-OCS, PADUA ABBR––––0.410.390.460.370.350.530.470.44––––0.100.240.110.350.250.250.320.21––––––––––––––––Moore et al. [40]IrelandChildren (12 y)93p161pLOCI-CV0.6780.3000.3610.406Fagnani et al. [41]ItalyAdult (23–24 y)159p180pSCL-900.470.170.451 (0.099–0.586)0.000 (0.000–0.267)0.549 (0.415–0.711)Iervolino et al. [42]UK*TwinsUK adult twin registerAdults women(17–86 y)27201635OCI-R0.47 (0.40–0.53)––0.28 (0.19–0.36)–––0.380 (0.187–0.526)0.090 (0.000–0.252)0.530 (0.472–0.595)Lahey et al. [43]USA*Tennesse Twin StudyAdolescents(6–17 y)Not describedCAPS0.640.320.640 (0.457–0.684)0.000 (0.000–0.166)0.360 (0.316–0.411)Mataix-Cols et al.
