RT Article T1 Twin closeness and co-twin risk for substance use disorders: Assessing the impact of the equal environment assumption A1 Labuda, M. C. A2 Svikis, D. S. A2 Pickens, R. W. LA English YR 1997 UL https://krimdok.uni-tuebingen.de/Record/1639917209 K1 Drogenkonsum K1 Zwillinge