Geels et al.  examined cohort differences in adolescent alcohol use (AAU) and its ‘genetic architecture’ (G) among two cohorts of Dutch twins aged 13–21 years surveyed in 1993 and 2005–08. They found no differences in heritability but did find earlier initiation of alcohol use, more frequent use and greater quantity of use in the 2005–08 cohort compared to the 1993 cohort. Additionally, males drank more frequently and in greater quantity than did females. Given that a focus on heritability has its limits , and may not be useful when making comparisons over time or between cohorts , our commentary focuses upon issues raised by the results about environment (E).
Geels et al.'s  findings raise concerns about environmental factors involved in: (1) the increase in initiation, frequency and quantity of alcohol use among 13–15-year-olds; and (2) the increase in quantity of alcohol use across ages. These increases place Dutch youth at greater risk for developing alcohol use disorders and have important implications for public health, policy, education and clinical practice in the Netherlands. The authors note that other European countries have relatively stable alcohol use patterns among youths, suggesting that the Netherlands may represent a special case that warrants additional inquiry. Efforts are under way to identify environmental strategies to help prevent alcohol abuse among adolescents in Europe, including the Netherlands (e.g. project AAA–Prevent). More refined year-by-year data may help to pinpoint the time and slope of AAU increases among Dutch youths. This information can, in turn, help to identify potential environmental and socio-cultural factors involved in these increases.
Geels et al.  found an 11% increase in alcohol use initiation (from 62 to 73%) among 13–15-year-olds in the 2005–08 cohort, with 78% drinking once a month or less and 78% drinking less than one glass per week. Thus, while most 13–15-year-olds were not drinking very frequently or in great quantity, the overall trend towards larger quantities of alcohol use across age groups is concerning. The authors suggest that this trend may be due to adolescents having more spending money and to the increased availability and popularity of pre-mixed alcoholic drinks. However, despite similar conditions in the United States, a comparison of US cohorts in 1993 and 2005–08 suggest decreases in alcohol use and having been drunk . To address the increase in alcohol use effectively among youth in the Netherlands before it escalates into a public health crisis, a number of questions must be addressed. First, specific socio-cultural factors associated with the observed trends must be identified, as those offered by the authors are not associated with similar trends in other nations. Secondly, effective strategies must be identified to minimize the nefarious consequences of early drinking. Such strategies, reviewed by Babor et al. , include alcohol taxes, restricting physical availability of alcohol, marketing restrictions and screening, brief intervention and treatment when warranted.
Increases in alcohol use across cohorts is problematic, and probably environmentally influenced. However, Geels et al.'s  results show more shared environmental influences on differences in alcohol initiation and more genetic influences on differences in quantity and frequency of alcohol use. Thus, environmental interventions for delaying alcohol initiation might target all youths most effectively, while interventions to reduce quantity and frequency of use might best be applied to those youth at highest genetic risk. AAU prevention and intervention efforts may benefit from incorporating a developmental perspective such as Brown's  notion of double developmental synthesis, whereby researchers consider normative developmental processes (e.g. biological, cognitive, social–emotional and behavioral changes) in conjunction with addiction processes. Given that early initiation of alcohol use is associated with other problem behaviors and that such behaviors may reflect a latent tendency towards disinhibition , one promising intervention strategy is to target problem behaviors in general. One such intervention is ‘Communities That Care’, a community-based approach to reducing problem behaviors in youth that was developed in the United States and that has been implemented in the Netherlands .
Future implementation efforts may benefit from the burgeoning field of implementation science, the ‘scientific study of methods to promote the systematic uptake of research findings and other evidence-based practices into routine practice, and, hence, to improve the quality and effectiveness of health services’. Successfully implementing effective interventions is challenging; however, translating research into practice is important to ensure global public health. Given the importance of adolescence and emerging adulthood to subsequent adult functioning, identifying and successfully implementing strategies to delay the initiation of alcohol use and to minimize the progression of use to problematic levels is crucial to individuals and to a nation's health.