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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 2b.

Tetrachoric correlations (and 95% confidence intervals) in DZ male–male twin pairs within and between cannabis, stimulant and sedative abuse (N = 1219).

Male DZ pairs Twin 1 cannabis Twin 1 stimulant Twin 1 sedatives Twin 2 cannabis Twin 2 stimulants
Twin 1 stimulant 0.90 (0.76; 1.00)
Twin 1 sedatives 0.82 (0.61; 1.00) 0.90 (0.74; 1.00)
Twin 2 cannabis 0.53 (0.21; 0.86) – –
Twin 2 stimulants 0.46 (0.03; 0.89) – – 0.77 (0.57; 0.97)
Twin 2 sedatives – – – 0.50 (0.07; 0.93) 0.88 (0.70; 1.00)