Basic characteristics of the study samples used in (A) genetic association analyses (N = 1428) and (B) logistic regressions (N = 1296).

a, 74 with unconfirmed zygosity; b, 34 with unconfirmed zygosity; c 44 with unconfirmed zygosity; d 23 with unconfirmed zygosity: *, Conditioned for regular smoking.MZ, monozygotic; DZ, dizygotic; CPD, cigarettes per day; DSM-IV, Diagnostic and Statistical Manual of Mental Disorders, 4th edition (APA 1994); MDD, major depressive disorder; ND, nicotine dependence.a组74例合子性未明确；b组34例合子性未明确；c组44例合子性未明确；d组23例合子性未明确：* 经筛选为规律吸烟者。MZ（monozygotic，单合子）；DZ（dizygotic，双合子）；CPD（cigarettes per day，日均吸烟支数）；DSM-IV（Diagnostic and Statistical Manual of Mental Disorders, 4th edition，《精神障碍诊断与统计手册（第四版）》，美国精神病学会1994年版）；MDD（major depressive disorder，重性抑郁障碍）；ND（nicotine dependence，尼古丁依赖）