Previous studies have indicated that the younger the age people in the United States are when they begin drinking, the greater the likelihood they will experience alcohol dependence during their life time12,13. Analyses presented in this report indicate that even after analytically controlling for personal history of alcohol dependence and other respondent characteristics related to age of drinking onset, the younger people are when they start drinking, the more frequently they report drinking 5+ drinks or to intoxication. For example, compared to persons who started drinking at age 21, those who started at age 14 were 2.8 times more likely to drink to intoxication on at least one day each week in the past year. 

Previous research has also shown that raising the drinking age to 21 reduces alcohol-related traffic deaths and other unintentional injury deaths among persons under age 21 9,10. This report raises the possibility that efforts to delay drinking onset may be associated with reductions in traffic and other unintentional injuries under the influence not only among persons under the age of 21, but also among those above the legal drinking age. After controlling for respondent characteristics related to age of drinking onset including measures of current and life time alcohol dependence and the frequency respondents drank 5+ drinks during their period of heaviest drinking, persons who started drinking in each age group under 21 relative to those starting at age 21 and older were significantly more likely to have placed themselves in situations after drinking that increased their risk of injury. They were also significantly more likely to have been accidentally injured during their lifetime under the influence of alcohol. 

The relationship between early age of drinking onset and injury involvement under the influence was found not only over the course of the respondent's life but in the year prior to the survey as well. However, our analyses indicate that a large part of the relation between early onset of drinking and past year injury involvement results from those who started drinking at younger ages drinking heavily more frequently in the past year (regardless of whether they were alcohol dependent). Persons who started drinking prior to age 18 were also significantly more likely to place themselves in situations after drinking that increased their risk of injury even after controlling for past year alcohol dependence and frequency of heavy drinking. 

We should caution that the results of this study were based on self-report in a cross sectional survey, where data are collected at one point in time from a sample selected to describe a larger population at that time (see Babbie E. Survey Research Methods)20 and hence may be subject to limitations associated with self-report. On the one hand, social desirability biases may lead to underreporting of alcohol use and injury involvement after drinking. On the other hand, persons willing to report heavy drinking may be less hesitant than others to report injury involvement after drinking. Although the sample was nationally representative, very large and the 90 percent response rate was excellent, it would be useful to replicate these results in a longitudinal study with chemical markers in addition to self-report. 

Also, it should be noted that it is possible that people who engage in a variety of deviant or illegal behaviors at an early age are more likely to continue them later in life. However, the relationships between early drinking onset and recent heavy drinking and injury involvement were independent of the current or past use of illegal drugs or tobacco. 

Our findings point to a need for additional research in two areas. First there is a need for research that explains why starting to drink at an early age relates alcohol dependence to heavier drinking later in life even among persons who are not dependent. Genetics may play a role by predisposing certain individuals to exhibit tolerance to physiologic effects of alcohol early in their drinking careers thereby contributing to the establishment of heavier drinking patterns later in life.21 Familial sources including both shared genetic and environmental may account for the early onset later dependence relation.22 Persons who drink earlier may have physiologic changes that contribute to greater tolerance and the need to drink more to achieve the same pleasurable sensations after drinking. Persons who start drinking earlier in life may learn to drink in less controlled situations with peers whose drinking norms are to drink to intoxication rather than with family and parents whose norms might tend more towards moderate drinking. 

Second, there is also a need for research examining why even when diagnosis of alcohol dependence and measures of frequency of lifetime and past year heavy drinking are controlled, persons who began drinking at an earlier age are more likely to place themselves in situations that pose risk of injury. Several explanations are possible. Those who begin drinking at an early age may be less fearful of injury and situations that pose risk of injury. Some may derive pleasure or a sense of self-esteem by taking risks associated with injury. It is well known that persons who drive after drinking, for example, are more likely to speed and are less likely to wear seat belts.23 Alternatively, persons who start drinking at earlier ages may not be as aware or appreciate how alcohol increases injury risk. Other studies have shown that people who drive after heavy drinking are more likely to believe they can drive safely after higher amounts of alcohol consumption.24 They may believe for example the risk of traffic crashes and other injuries increase only for people who are visibly intoxicated.

In sum, this study indicates that early onset of drinking increases frequent heavy drinking which in turn heightens risk of alcohol related injuries among persons under the legal drinking age of 21 and among adults over age 21 not only for persons with diagnosable alcohol dependence, but other drinkers as well. Further, those who begin drinking at an early age report more often placing themselves ever, and in the past year, in situations after drinking that increase risk of injury. That was found not only among alcohol dependents and others who more frequently drink heavily and to intoxication but other drinkers as well. Physicians and other health care providers should counsel their patients who start drinking at an early age not only about their increased risk for alcohol dependence, but also their increased risk of experiencing unintentional injury under the influence of alcohol. 

Recent national surveys indicate that after a decade of decline, the percentage of high school seniors who drink, drink heavily and drive after drinking has increased in the past two years.25 The study reported here identifies important new reasons to expand clinical, educational, legal and community interventions that delay onset of drinking.