Cox-proportional hazard analysis using age at onset of habitual smoking censored at non-habitual smokers. KapoorManav WangJen-Chyong BertelsenSarah BucholzKathy P. BuddeJohn HinrichsAnthony AgrawalArpana BrooksAndrew ChorlianDavid DickDanielle HesselbrockVictor ForoudTatiana KramerJohn KupermanSamuel ManzNiklas Nurnberger JrJohn PorjeszBernice RiceJohn TischfieldJay XueiXiaoling SchuckitMarc J. EdenbergHoward J. BierutLaura M. GoateAlison 2013 1<p>Analysis was performed within family clusters using additive model. Age at interview in quartiles, gender, pc1, parental smoking and parental drinking were included as covariates.</p>2<p>Nominal P values are shown uncorrected for multiple testing. The Bonferroni-corrected significance threshold is Pā€Š=ā€Š0.005.</p>