Why are some people who start smoking in their early teens hooked on cigarettes for life, while others find it relatively easy to give up? Scientists at the University of Utah show that genetic differences are part of the answer.

Their research, published on the 11 July in the journal PLoS Genetics, focuses on variations in a gene that determine the structure of the “nicotine receptor” – the protein in the brain that interacts with nicotine, the most addictive chemical in cigarette smoke.

The researchers studied DNA samples from 2,827 long-term smokers. They assessed the level of nicotine dependence and recorded the age at which people began smoking, the number of years they smoked and the average number of cigarettes smoked a day.

One variant of the gene put smokers at greater risk of heavy nicotine dependence as adults but only if they started smoking regularly before the age of 17. A second variant reduced the risk of later addiction.

The authors conclude: “Identification of genetically high-risk individuals who would benefit from proactive interventions, such as adolescent education and cessation clinics, may result in a population with a lower rate of adult nicotine addiction.”

为何有些从十几岁开始吸烟的人，一辈子都摆脱不了香烟，而其他人戒严却相对容易呢？美国犹他大学(University of Utah)的科学家表示，基因差异是造成这种现象的原因之一。

他们的研究结果7月11日发表在公共科学图书馆（Public Library of Science，简称PLoS）遗传学期刊上，着重于研究决定“尼古丁受体(nicotine receptor)”结构基因的变体。尼古丁受体是大脑中的一种蛋白质，它可与香烟烟雾中最令人上瘾的化学成分尼古丁互相作用。

研究人员调查了2827名长期吸烟者的DNA样本。他们对每名吸烟者的尼古丁依赖水平做出评估，并记录下他们开始吸烟时的年龄、有多少年吸烟史以及平均每天吸多少支烟。

如果17岁前就开始有规律地吸烟，该基因的一种变体可加大该吸烟者在成年后对尼古丁产生严重依赖的风险。而该基因的另一种变体则可以降低成年后对尼古丁上瘾的风险。

研究报告的作者总结道：“找出那些在基因上容易上瘾的人，有助于对他们进行积极干预，如进行青春期教育和戒烟治疗，这将降低成年人中对尼古丁上瘾的人口比例。”