Heavy drinking and alcohol use disorder (AUD) contribute substantially to morbidity and mortality worldwide (
1,
2), mainly through liver disease, injury, cancer, cardiovascular disease, and impaired psychosocial functioning (
3,
4). However, few individuals receive treatment for problematic drinking (
5–
8), often because they are not interested in abstinence, the goal most commonly offered in treatment settings (
9–
11). Recently, nonabstinent drinking reduction treatment goals, which may be more attainable and engage more people in treatment, have gained attention (
12,
13). Psychopharmacological treatments successfully reduce drinking to nonabstinent levels (
14–
16), and reductions are maintained over time (
17) and are associated with decreased mortality (
14), improved health, and reduced negative consequences of drinking in clinical and general population samples (
17–
23). In these studies, drinking reduction was measured using the World Health Organization (WHO) risk drinking levels, a gender-specific metric indicating the level of risk associated with the average daily amount of alcohol consumed: very high risk, high risk, moderate risk, and low risk (
24).
Recent studies and a meta-analysis (
25) of time trends in alcohol consumption among U.S. adults show increases in any alcohol use (
25–
27) and in heavy use (binge drinking) (
25,
26), specifically among women (
25,
26,
28,
29). However, none of these studies measured consumption using the WHO risk drinking level definitions. What is known about the prevalences of the WHO levels was estimated in older data (2001–2002), in which 2.5% of current drinkers were at very high risk, 2.5% at high risk, 4.8% at moderate risk, and 90.2% at low risk (
18). However, more recent prevalence data are lacking, and whether the prevalences of WHO risk drinking levels have changed over time and whether there are differences between men and women remain unknown. Furthermore, reports on the relationships between the WHO risk drinking levels and clinically important drinking consequences—for example, alcohol dependence (
18), drug dependence (
23), reduced quality of life (
19,
21), mental health functional impairment (
18), impaired liver function (
17,
21), liver disease (
20), and anxiety and depressive disorders (
22)—used data collected over 15 years ago. Additionally, the relationships between alcohol use and its consequences differ in men and women (
30). Given the many changes in U.S. society and the prevalence of alcohol-related conditions (
26,
31–
41), updated information is needed on the associations of health conditions with the WHO risk drinking levels, overall and by gender.
To examine these issues, we used data on U.S. adults from two nationally representative surveys, the 2001–2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) (
42) and the 2012–2013 NESARC-III (
8). First, we determined whether prevalence of WHO risk drinking levels changed between the 2001–2002 and 2012–2013 surveys, as well as whether changes varied by gender. Second, we examined whether health conditions related to alcohol (alcohol dependence, AUD, drug dependence, drug use disorders, functional impairment, liver disease, and depressive and anxiety disorders) were associated with WHO risk drinking level within each survey and whether these associations differed by gender.
Discussion
In previous studies, the WHO risk drinking levels (very high, high, moderate, and low) were associated with physical, mental, and social functioning and reduction in the WHO risk drinking categories predicted improvement in these conditions (
17–
23). Thus, the WHO risk levels show potential clinical utility as a treatment outcome measure (
14–
17,
19,
21). However, important epidemiological information was lacking, namely, whether the prevalence of the WHO risk levels changed over time, associations of these levels with clinical correlates of heavy drinking in newer data, and whether results differed by gender. In adult general population current drinkers, the prevalence of moderate, high, and very high risk levels was significantly greater in the 2012–2013 survey than in the 2001–2002 survey, with a greater increase in prevalence of the very high risk drinking level among women than among men. Health conditions (AUD, drug use disorders, functional impairment, liver disease, depressive and anxiety disorders) were associated with risk levels within each survey, among men and women.
Increases over time in moderate, high, and very high risk drinking are similar to results from other U.S. national studies, which show increases in alcohol consumption, specifically binge drinking (any or weekly), particularly among women (
25,
26,
28,
29). Increases in heavy drinking among women are concerning, as women are less likely to receive treatment (
73) yet may be more likely than men to develop health consequences at comparable consumption levels (
30). Additional studies should identify the drivers of these patterns (
41). Inconsistent with previous studies, the present study showed an increase in moderate drinking among men. This study differs from the others in two key ways: an important and widely recognized consumption measure and analysis conducted in current drinkers. One previous study of current drinkers showed no increase in binge drinking in men or women (
28), suggesting that binge drinking and the WHO risk drinking levels measure alcohol consumption differently. As a metric of alcohol consumption, the WHO levels are particularly useful, as they categorize drinkers on the basis of intensity and frequency of drinking and identify which drinkers are at greatest risk for alcohol-related consequences (
24).
In both surveys, higher WHO risk drinking levels were associated with clinically important health conditions (alcohol dependence/AUD, drug dependence/drug use disorders, functional impairment, liver disease, and depressive and anxiety disorders), similar to previous studies (
18,
20,
22,
23), suggesting that they are a valid characterization of alcohol consumption. Alcohol dependence, AUD, drug dependence, and drug use disorders were associated with all three risk levels (moderate, high, and very high versus low). Functional impairment was associated with very high and high risk, the categories of greatest clinical concern (
18). Liver disease and depressive and anxiety disorders were associated with very high risk drinking. Generally, the prevalence of these health conditions was greater in the very high and high risk levels, indicating that increased drinking shows increased risk, and suggesting that reducing drinking to moderate or low risk levels could reduce such conditions.
Associations were generally similar for women and men, with some differences, mainly in the 2012–2013 survey. Women showed stronger relationships of very high risk drinking to functional impairment and depressive and anxiety disorders than men, similar to previous studies in AUD samples (
74–
76). Men showed a stronger relationship of moderate risk drinking to AUD than women. These differences may reflect the fact that, generally, men show higher prevalence of AUD and women show higher prevalence of depression and anxiety, emphasizing the need for further studies in women examining the relationship between drinking and functional impairment, depression, and anxiety.
While causality cannot be determined in these cross-sectional data sets, modeling alcohol consumption as preceding the outcomes (health conditions) is supported by the following. By definition, drinking precedes AUD. Drinking has an impact on liver function, causes liver disease, and exacerbates liver disease due to other causes (
3). Heavy drinking/AUD leads to functional impairment due to mental health issues (
77). Drug use disorders and depressive and anxiety disorders are highly comorbid with alcohol use/AUD (
5,
8,
42,
67,
78), with some (but not all) studies showing alcohol use/AUD preceding the comorbid disorders (
79). In longitudinal studies, reduction in drinking was found to be associated with reduced likelihoods of these outcomes (
18,
20,
22,
23), justifying the inference about directionality modeled here. Further studies are warranted to better understand the complex and possibly reciprocal relationships between drinking and these conditions.
This study had several limitations. While the direction of effect modeled was well supported, cross-sectional data cannot determine causality. Data were based on self-report, leading to the possibility that response bias could contribute to the findings. A higher response rate for NESARC-III would be preferred, since survey respondents may be healthier than nonrespondents (
80), and thus the prevalence of risky drinking and health conditions may be underestimated. Diagnoses were not made by clinicians, because clinician-administered interviews are not feasible in large-scale epidemiological surveys. Future studies of health conditions could incorporate direct examinations or medical record variables. Participants were not asked whether alcohol was the cause of their liver disease, but even in those with liver disease from other causes, alcohol use leads to further damage and a worse prognosis (
3). Liver disease had low prevalence, especially among women. For depressive and anxiety disorders, the diagnostic systems could not be perfectly aligned, because DSM-IV diagnoses were used in the 2001–2002 survey and DSM-5 diagnoses in the 2012–2013 survey. However, the effect of these DSM differences should be small for a combined depressive/anxiety disorder variable, because some diagnoses would be made in both systems (
81).
The study had several strengths as well: nationally representative data were used, with a sample large enough to include all the WHO risk drinking levels; there was representation of participants by gender, age, race/ethnicity, and socioeconomic status; the assessment of alcohol consumption and health conditions was detailed, rigorous, and consistent; and diagnoses were reliable and valid.