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. Author manuscript; available in PMC: 2016 Apr 1.
Published in final edited form as: Drug Alcohol Depend. 2015 Jan 28;149:49–54. doi: 10.1016/j.drugalcdep.2015.01.016

Table 2a.

Tetrachoric correlations (and 95% confidence intervals) in MZ male–male twin pairs within and between cannabis, stimulant and sedative abuse (N = 1720).

Male MZ pairs Twin 1 cannabis Twin 1 stimulant Twin 1 sedatives Twin 2 cannabis Twin 2 stimulants
Twin 1 stimulant 0.73 (0.54; 0.92)
Twin 1 sedatives 0.92 (0.83; 1.00) 0.82 (0.66; 0.98)
Twin 2 cannabis 0.92 (0.83; 1.00) 0.62 (0.36; 0.88) 0.67 (0.42; 0.92)
Twin 2 stimulants 0.52 (0.21; 0.83) 0.90 (0.79; 1.00) 0.61 (0.31; 0.92) 0.80 (0.67; 0.92)
Twin 2 sedatives 0.81 (0.63; 1.00) 0.66 (0.36; 0.95) 0.81 (0.60; 1.00) 0.90 (0.77; 1.00) 0.80 (0.58; 1.00)