The finding of a stronger genetic risk in early-onset smokers supports public health interventions to reduce adolescent smoking. However, of the variables evaluated in this study, the strongest single risk factor of heavy smoking is early-onset smoking, highlighting the importance of a reduction in adolescent smoking across the entire population, not just in individuals with the risk allele of rs16969968. Nonetheless, there is a robust debate on whether policy and other interventions aimed at curbing early use would have significant effects on the development of dependence and related health problems over the long term. Although early use is associated with greater vulnerability to addiction,9,24 early use is also associated with a variety of behaviors reflecting a vulnerability already in place before the onset of use.37 Accordingly, early use may not cause greater vulnerability to addiction; instead, early use and vulnerability to addiction may have a shared etiology.
