The Epidemiology of Alcohol and Drug Disorders

Alcohol Consumption

The use of substances to alter mood states has been a part of civilization from prehistoric through modern time periods. Archeological records document the conversion of sugar into fermented beverages for recreational use, as part of religious ceremonies, and as an analgesic or disinfectant as early at 10,000 BCE. Alcohol remains incorporated in the fabric of many cultures for a variety of uses, including social and recreational use, as a part of religious ceremonies and secular festivities, and as a normative aspect of daily life. Furthermore, moderate consumption is associated with health and longevity, and is considered to be protective against several adverse health outcomes including cardiovascular disease.

Long-term historical information on US alcohol consumption is available through per-capita alcohol consumption statistics derived from sales records. These records show that drinking levels in the United States varied greatly over time from the early days of the United States to the 21st century. Per-capita consumption ranged from extraordinarily high levels during the US colonial period (from an estimated 5.8 gallons per year per capita in 1790 to 7.1 gallons in 1830) to very low levels before and during Prohibition (from an estimated 1.96 gallons in 1916 to 0.97 gallons in 1934). Prohibition refers to the period during which the United States prohibited the manufacture, sale, and transportation of alcoholic beverages by the 18th Amendment to the US Constitution. This period began in 1920 and ended in 1933 with the repeal of the 18th Amendment by the 21st Amendment.

From 1935 until 1982, shown in Fig. 2.1 , per-capita alcohol consumption increased steadily to a peak of nearly 2.8 gallons of ethanol per year in 1982. After that, consumption declined until the late 1990s, and then began to increase again.

These data are generally consistent with US general population survey data from 2001–2002 to 2012–2013, showing an increase in the prevalence of drinking, as well as volume and frequency of drinking and prevalence of at least monthly heavy episodic drinking among drinkers. Liver cirrhosis mortality statistics show similar variations over time, including an uptick in alcohol-related liver cirrhosis mortality since 2009, especially notable in young adults 25–34 years of age.

Worldwide, alcohol consumption patterns vary considerably. Consumption is lowest in predominantly Muslim countries (e.g., individuals in Afghanistan and Pakistan consume 0.03 and 0.31 pure alcohol per capita, respectively) and eastern Mediterranean countries, and highest in eastern European countries (e.g., individual in Ukraine and the Russian Federation consume 15.58 and 15.23 L pure alcohol per capita, respectively) and western European countries such as France, Germany, and the United Kingdom.

Alcohol consumption is also heterogeneous within countries. For example, about one-third of US adults do not drink, although US per-capita consumption is 2.32 gallons per year. Abstainers are rare in Eastern Europe (including Russia and Ukraine), where per-capita consumption is the highest in the world. After immigration, immigrants tend to retain the drinking levels of their country of origin rather than hanging onto the patterns of their new country, for example, Mexican immigrants in the United States and Russian immigrants in Israel.

Drug Use

Drugs such as cannabis, opium, and cocaine have been cultivated and used medicinally as well as recreationally for centuries. Opium poppies are believed to have been first grown in the region near modern-day Iraq as early as 3400 BCE. Opium was used primarily as an analgesic and anesthetic, but medical use did not become widespread until the development of the hypodermic needle in the early 1800s. Historical analysis also indicates that marijuana was smoked recreationally and medically in ancient China as early as 2737 BCE. In South America, societies have grown and consumed coca, the plant grown to create cocaine, for centuries. The most common mode of administration is to chew the leaves of the coca plant, or to mix the leaves into a tea. In the 20th century, innovations in pharmacological knowledge led to the development of synthetic drugs such as lysergic acid diethylamide, categorized as a hallucinogen, and methylenedioxymethamphetamine (or “ecstasy”), categorized as an amphetamine.

In Western countries prior to the 1960s, drug use was rare and the few studies that addressed prevalence focused on heroin, with widely varying results. Morphine is believed to have been prescribed often in the 19th and early 20th centuries mainly as a cough suppressant to ease the suffering of individuals with tuberculosis, although no data are available to empirically estimate incidence and prevalence. During the Civil War, it is believed that more than 400,000 soldiers became dependent on morphine, as it was liberally prescribed for pain associated with battle wounds.

Systematic surveys of US drug use began in the 1960s with a series of national household surveys on drug use conducted by the National Institute on Drug Abuse (NIDA) and later by the Substance Abuse and Mental Health Services Administration (SAMHSA). These were originally known as the Household Surveys on Drug Use, and are now known as the National Survey on Drug Use and Health (NSDUH ). A series of three national surveys conducted by the National Institute on Alcohol Abuse and Alcoholism have also provided important information on US adult alcohol and drug use in the years 1991–1992, 2001–2002, and 2012–2013. The survey conducted in 1991–1992 is known as the National Longitudinal Alcohol Epidemiologic Survey (NLAES ). The survey conducted in 2001–2002 is known as the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC ). The third survey, conducted in 2012–2013, is known as the National Epidemiologic Survey on Alcohol and Related Conditions III (NESARC-III).

Earlier, Household Surveys on Drug Use surveys showed that illicit drug use, especially marijuana, increased greatly after the late 1960s. Heroin use also increased in the late 1960s, when the profile of users changed from “bohemians” to inner-city, unemployed males.

More recent NSDUH data on adults provides time trend information from 2002 to 2013 ( Fig. 2.2 ). This shows that since about 2007, drug use has increased in the US general population, largely driven by increases in the use of marijuana. More detailed examination of NSDUH marijuana data shows increases in adults age 18 or older since 2007 in use, daily/near-daily use, and other cannabis indicators, with increases particularly concentrated within male users from lower income families The increases in marijuana use since the early 2000s are consistent with findings from the NESARC (2001–2002) and NESARC-III (2012–2013 ^, ), which also show marked increases in marijuana use among adults, including men, younger individuals, and those from lower-income households.

An area of illicit drug use that has become a source of much concern over the last 10 years is prescription opioids, largely fueled by an epidemic of unintentional fatal opioid overdoses, which became a leading cause of injury death and hospital admissions. NSDUH data show increases in nonmedical use of prescription opioids up to about 2006, and a steadying in these rates among adults aged 26 or older, and some decline in the 12–17 and 18–25 age groups. NESARC data show that between 2001–2002 and 2012–2013, nonmedical opioid use increased among adults, as did heroin. NSDUH data do not show overall increases in cannabis use in adolescents 12–17 years of age since 2002.

Another source of information on drug use among adolescents is the Monitoring the Future (MTF) series of annual national surveys of 8th, 10th, and 12th grade students. MTF data since 1991 show that in 1991, 44.1% of 12th graders had ever used an illicit drug, increasing to 54.3% in 1997, and decreasing to 48.9% in 2015. In 1991, 18.7% of 8th graders, 30.6% of 10th graders, and 44.1% of 12th graders had ever used an illicit drug. By 1997, these had increased to 29.4%, 47.3%, and 54.3%, respectively. In 2015, the prevalences were 20.5%, 34.7%, and 48.9%, respectively. By far the most commonly used drug was marijuana (15.5%, 31.4%, and 44.7% among 8th, 10th, and 12th graders in 2015).

Substance Disorders in the Diagnostic and Statistical Manual of Mental Disorders

For SUDs, DSM-IV provided diagnostic criteria for two disorders, dependence and abuse ( Table 2.1 ), as well as symptoms for diagnosing substance-specific intoxication and withdrawal syndromes, and methods for diagnosing substance-induced psychiatric disorders. Note that DSM-IV-TR, published in 2000, provided updated text but did not change the diagnostic criteria. The DSM-IV substance dependence criteria, shown in Table 2.1 , are based on the alcohol dependence syndrome, which was generalized to drugs in 1981. Dependence was considered a combination of physiological and psychological processes leading to increasingly impaired control over substance use in the face of negative consequences. Dependence was considered one “axis” of substance problems, and the consequences of heavy use (social, legal, medical problems, hazardous use) considered a different axis of substance problems. This biaxial concept led to the distinction between abuse criteria (social, role, legal problems, or hazardous use, most commonly driving while intoxicated) and dependence (tolerance, withdrawal, numerous indicators of impaired control over use).

The focus on dependence is based on its centrality in research and on its psychometric properties. DSM-IV defined dependence similarly to the definition found in the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). These definitions had good to excellent reliability across samples and instruments, ^a

a References 25, 27, 95, 122, 123, 125, 300.

with few exceptions (rare substances; hallucinogens). Dependence validity has also been shown to be good via several study designs. These include multimethod comparisons ^b

b References 46, 91, 125, 132, 246, 259, 270.

; longitudinal studies ^c

c References 93, 121, 122, 127, 267, 269.

; latent variable analysis ; and construct validation. Animal models of a syndrome of cocaine dependence symptoms (as distinct from use patterns) lend credence to the dependence syndrome not only as a cross-cultural phenomenon, as suggested by a World Health Organization (WHO) study but as a cross-species phenomenon as well.

Substance abuse was a different case. Contrary to clinical assumptions, abuse did not necessarily lead to dependence. ^d

d References 93, 121, 127, 133, 267, 269.

Furthermore, not all cases of alcohol or drug dependence manifested abuse symptoms. Dependence is more familial than abuse is. DSM-IV–defined alcohol abuse was most often diagnosed in the general population based on one symptom, driving while intoxicated ; preliminary analyses of national data show this was also the case for drug abuse. The DSM-IV definition of abuse was problematic in that it depended on the availability of a car, while dependence was a heritable, complex condition.

Various psychometric analyses were conducted to examine the validity of the Edwards and Gross taxonomy of two distinct, correlated factors for substance abuse and dependence criteria prior to the start of the DSM-5 Substance-Related Disorders Workgroup (of whom one of the authors, DH, was a member). Confirmatory factor analysis on the alcohol abuse and dependence items provided mixed evidence; several studies show that a two-factor model best described abuse and dependence items but with very high correlations between the factors, whereas several other studies found evidence of similar model fit for one- and two-factor models and selected the one-factor model on the basis of parsimony and high factor correlations. Factor analyses of cannabis abuse and dependence items have generally found support for a one-factor model or similar fit of one- and two-factor models, although results from a general population survey support a two-factor model. Taken together, these studies showed some support for combining abuse and dependence, albeit with some evidence to the contrary. Differences across studies may also have occurred due to characteristics of the populations studied (e.g., general population versus community sample, adults versus adolescents).

One of the main issues for the DSM-5 Substance-Related Disorders Workgroup was how to address the distinction between abuse and dependence. Workgroup members and other investigators conducted many studies of the dependence and abuse criteria in different adolescent and adult samples and populations. These studies were based on Item Response Theory (IRT) analyses, which provide more nuanced information on the relationship of abuse to dependence symptoms than the factors analyses that had been done before. By the time DSM-5 criteria were finalized, studies on this issue had included more than 200,000 participants. Results were very consistent: abuse and dependence formed a single, unidimensional construct, leading the DSM-5 Substance-Related Disorders Workgroup to eliminate the distinction between abuse and dependence, and combine most of the criteria into a single disorder (see Table 2.1 ). Additional changes of note in DSM-5 were the addition of a craving criterion, removal of the DSM-IV legal problems criterion, and addition of a withdrawal criterion for cannabis, since considerable evidence had accumulated since DSM-IV that a cannabis withdrawal syndrome existed.

Substance Disorders: A Categorical or Dimensional Trait?

Recent psychometric analyses of the substance abuse and dependence criteria have suggested that these disorders are not categorical entities; instead, evidence supports an underlying continuum of alcohol severity across a variety of samples and populations. ^e

e References 136, 169, 197, 217, 245, 261.

Such information may be critical when statistical power is limited, as it often is in studies of gene-gene or gene-environment interaction. The DSM-5 addressed this issue by providing definitions of mild, moderate, and severe SUD: 2–3 criteria for mild, 4-5 criteria for moderate, and 6 or more criteria for severe.

Prevalence and Incidence of Substance Disorders

The most comprehensive epidemiologic US information on the incidence, prevalence, and psychiatric comorbidity of alcohol and drug disorders comes from the two NESARC surveys. The NESARC was a longitudinal survey of 43,093 respondents 18 years or older conducted in 2001–2002 with a 3-year follow-up of 34,653 respondents. The NESARC-III was a survey of a fresh sample of 36,309 participants conducted in 2012–2013. The diagnostic interview for both surveys was the Alcohol Use Disorder and Associated Disabilities Interview Schedule (AUDADIS), a structured interview for nonclinicians with high reliability and validity for SUDs. ^f

f References 27, 95, 105, 125, 141, 142, 260, 300.

The AUDADIS-IV was used to assess DSM-IV criteria for SUD and other disorders in the NESARC, and the AUDADIS-5 was used to assess DSM-IV and DSM-5 criteria for SUD in the NESARC-III, and DSM-5 criteria for other disorders.

In the NESARC, the prevalence of current (past 12 month) DSM-IV alcohol use disorder (abuse or dependence) was 8.5%, whereas the prevalence of lifetime DSM-IV alcohol use disorder was 30.3%. In the NESARC-III, the prevalence of current (past 12 months) DSM-5 alcohol use disorder was 13.3%, whereas the prevalence of lifetime alcohol use disorder was 20.1%. Corresponding DSM-IV rates of current and lifetime alcohol use disorder (12.7% and 43.6% in NESARC-III) showed that substantial increases had occurred in the prevalence of alcohol use disorders in the more recent NESARC-III. Current and lifetime alcohol disorders were more prevalent in men than women in both surveys, and compared with individuals of white race/ethnicity, blacks, Hispanics, and Asians had a lower prevalence of current and lifetime alcohol disorders in both surveys. In both surveys, alcohol disorder prevalence is inversely related to age; persons in younger age groups are most likely to have an alcohol disorder. As shown in the Wave 2 follow-up interview for the NESARC, the incidence of alcohol dependence was 1.66 per 100 person-years, meaning 1.66 cases per year of alcohol dependence for every 100 individuals without alcohol dependence at the beginning of that year. The incidence of alcohol abuse was slightly lower at 1.03 per 100 person-years. In general, predictors of incidence were similar to predictors of prevalence.

Drug disorders were substantially less common than alcohol disorders. In the NESARC, the prevalence of current (past 12 months) DSM-IV drug use disorder (abuse and dependence) was 2% for any current drug use disorder, whereas the lifetime prevalence was 10.3%. In the NESARC-III, the prevalence of current (past 12 months) DSM-IV drug use disorder (abuse and dependence) was 3.9% for any current drug use disorder, whereas the lifetime prevalence was 9.9%. Using DSM-IV criteria in the NESARC-III survey, current and lifetime prevalence of DSM-IV drug use disorder were 4.1% and 15.6%, respectively, indicating substantial national increases in the prevalence of drug use disorders in the United States between the two surveys. Of the substances, cannabis use disorders were the most common in both surveys. The past-year prevalence of DSM-IV marijuana use disorder was 1.5% in the 2001–2002 NESARC and 2.8% in the 2012–2013 NESARC-III, a substantial and significant increase ( P < .05) in prevalence.

Current and lifetime drug disorders are more prevalent in men than in women in both surveys. Drug disorder prevalence is inversely related to age; persons in younger age groups are most likely to have a drug disorder. There was no consistent trend by race for drug disorders. In the NESARC, incidence of drug dependence was estimated at 0.32 per 100 person-years of observation ; incidence of drug abuse was slightly lower at 0.28 per 100 person-years. In general, predictors of incidence were similar to predictors of prevalence.

The Course of Substance Disorders

Initiation of alcohol consumption and drug use often occurs during adolescence. Onset of alcohol abuse and dependence is most likely among individuals 18–29 years of age, although 15% of alcohol dependence cases begin before age 18. Often, substance disorders are not lifelong conditions. Indeed, a high rate of recovery has been documented in general population samples, even among individuals who have never sought treatment. Studies of alcohol disorders in the general population also show that a high proportion of recovered individuals return to moderate drinking as opposed to abstinence. Data from the NESARC has indicated that approximately 75% of individuals diagnosed with alcohol dependence at some point in the past did not have a current (i.e., past year) diagnosis, but that only about 20% of these individuals were abstinent from alcohol. Follow-up of this sample indicates that low-risk drinking represents a risk factor for relapse to an alcohol disorder compared with abstinence. However, using WHO indicators of very high risk, high risk, moderate risk, and low risk drinking, any shifts downward in WHO risk drinking levels from very high risk or high risk at baseline (2001–2002) to a lower level at the 3-year follow-up (2004–2005) was associated with a significant decrease in the likelihood of current alcohol dependence at follow-up.

The transition to adulthood represents a key developmental phase in which alcohol disorders often remit, in a process termed “maturing out.” Major predictors of recovery include key lifestyle components, such as employment, marriage, and childbirth. Whether or not these factors have a causal influence on recovery or reflect common factors underlying the positive lifestyle components and the recovery remains unknown.

Despite substantial progress in the development of treatments for alcohol and drug disorders, only about one-fifth of those individuals with an alcohol disorder and one-sixth of individuals with a drug disorder seek treatment for the condition during their lifetime. Furthermore, the delay from onset of disorder to treatment is typically 8–10 years. Finally, in contrast to sharp increases in treatment utilization for disorders such as depression between 1990 and 2003, a corresponding increase in the proportion of individuals seeking treatment for alcohol and drug disorders did not occur during this period. Data from NESARC-III continue to show poor rates of treatment for those with alcohol and drug use disorders.

The path from first use to dependence to treatment also differs by gender. Women who use alcohol and drugs often start using later than men, have a faster progression from first use to dependence, and enter treatment sooner than men given equal ages of dependence onset, although no such differences have been observed for crack-cocaine users. This phenomenon has been termed “telescoping.”

Evidence is accumulating that these well-documented gender differences in the course of alcohol disorders are converging. Studies of adolescent alcohol use have consistently shown a convergence in rates of alcohol and drug use initiation in younger birth cohorts, especially those born after World War II. Furthermore, several genetically informative samples have researched gender differences in DSM-IV–defined alcohol and drug disorders over time, also finding support for such a convergence. Similarly, large, representative cross-sectional studies in the United States support gender convergence in rates of DSM-IV–defined alcohol abuse and dependence. Finally, evidence indicates that the traditional “telescoping” phenomenon whereby women exhibit later onset of use and disorder but earlier treatment and shorter course may be diminishing, as women are more closely approximating men in both onset and course of disorder. Searches into the causes of these shifts are ongoing, but this evidence indicates increased social acceptability of alcohol use by women in younger generations.

Availability—Temporal and Geographical