Table 2c.

Tetrachoric correlations (and 95% confidence intervals) in male–male near-age sibling pairs within and between cannabis, stimulant and sedative abuse (N = 76,457).

Male near-age sibling pairs	Twin 1 cannabis	Twin 1 stimulant	Twin 1 sedatives	Twin 2 cannabis	Twin 2 stimulants
Twin 1 stimulant	0.85 (0.84; 0.87)
Twin 1 sedatives	0.80 (0.78; 0.82)	0.84 (0.82; 0.86)
Twin 2 cannabis	0.52 (0.49; 0.55)	0.47 (0.43; 0.50)	0.47 (0.42; 0.51)
Twin 2 stimulants	0.46 (0.43; 0.50)	0.51 (0.47; 0.54)	0.48 (0.43; 0.52)	0.83 (0.82; 0.85)
Twin 2 sedatives	0.46 (0.42; 0.51)	0.50 (0.46; 0.54)	0.53 (0.48; 0.57)	0.79 (0.77; 0.81)	0.85 (0.83; 0.86)