## INTRODUCTION

Sixty-nine percent of adult Americans—some 169 million people—report past-year alcohol use, dwarfing national rates of other substance use.1 While this high prevalence of drinking amplifies alcohol’s public health impact, it also helps normalize a range of drinking patterns. Drinking alcohol as normative behavior may explain, at least in part, the public’s lower perceived risk of harm from heavy alcohol use relative to even infrequent use of other drugs, some of which have fewer health consequences.1 Regardless, alcohol contributes to an estimated 88,000 deaths each year in the United States, making it the third leading cause of preventable death.2 Its impact also creates a significant drain on the economy, costing the U.S.$249 billion in 2010 (about U.S.$2 per drink).3 While it is possible to drink at a low-risk level, many Americans drink amounts that expose them to risk for a variety of negative health consequences, even if they do not meet criteria for an alcohol use disorder or have not yet experienced any negative consequences. It is therefore important to begin by defining different levels of consumption and their associations with health consequences.

## DEFINITIONS

Some alcohol use beyond abstinence may be considered low-risk use, although certain risks (such as cancers) may occur even with lower consumption. The National Institute on Alcohol Abuse and Alcoholism (NIAAA) defines low-risk consumption as no more than 4 drinks in a day and no more than 14 drinks per week on average for men, and no more than 3 drinks in a day, and no more than 7 drinks per week on average for women. These guidelines provide a useful framework, but drinking can be risky even within these limits under certain conditions (e.g., before driving or while taking a medication that may interact with alcohol) or for certain groups (e.g., children and adolescents, pregnant women, people with a family history of an alcohol use disorder, or people with medical conditions caused or affected by alcohol).4

Higher levels of alcohol consumption with or without consequences constitute unhealthy alcohol use, which is defined as any use that risks (or is accompanied by) a health consequence. Unhealthy use can be further stratified into risky use and alcohol use disorder (see Fig. 167-1).

###### FIGURE 167-1

Unhealthy alcohol use. (Source: Modified from Saitz R. New Engl J Med. 2005;352:598.)

Risky use is defined as use that increases the probability or risk of a negative consequence but has not necessarily yet resulted in one. Risky use is determined by either consumption levels (above the risk thresholds described above) or by any use by those at particular risk (e.g., family history of a disorder, as above). Alcohol use disorder, on the other hand, is determined by the recurrent consequences or symptoms experienced.

A diagnosis of ...

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