Prevalence and Co-occurrence of Substance Use Disorders and IndependentMood and Anxiety Disorders: Results From the National Epidemiologic Survey on Alcohol and RelatedConditions

Background  Uncertainties exist about the prevalence and comorbidity of substance use disorders and independent mood and anxiety disorders.

Objective  To present nationally representative data on the prevalence and comorbidity of DSM-IV alcohol and drug use disorders and independent mood and anxiety disorders (including only those that are not substance induced and that are not due to a general medical condition).

Design  Face-to-face survey.

Setting  The United States.

Participants  Household and group quarters' residents.

Main Outcome Measures  Prevalence and associations of substance use disorders and independent mood and anxiety disorders.

Results  The prevalences of 12-month DSM-IV independent mood and anxiety disorders in the US population were 9.21% (95% confidence interval [CI], 8.78%-9.64%) and 11.08% (95% CI, 10.43%-11.73%), respectively. The rate of substance use disorders was 9.35% (95% CI, 8.86%-9.84%). Only a few individuals with mood or anxiety disorders were classified as having only substance-induced disorders. Associations between most substance use disorders and independent mood and anxiety disorders were positive and significant (P<.05).

Conclusions  Substance use disorders and mood and anxiety disorders that develop independently of intoxication and withdrawal are among the most prevalent psychiatric disorders in the United States. Associations between most substance use disorders and independent mood and anxiety disorders were overwhelmingly positive and significant, suggesting that treatment for a comorbid mood or anxiety disorder should not be withheld from individuals with substance use disorders.

Substance use disorders and mood and anxiety disorders are widespreadamong the general population,^1-3 andare associated with substantial societal and personal costs.^4-7 Furthermore,national epidemiologic surveys^1-3 andnumerous clinical studies^8-12 consistentlyindicate that substance use disorders and mood and anxiety disorders havestrong associations when considered on a lifetime basis. However, consensushas not been achieved on the meaning and implications of the lifetime associationof these widespread disorders. Recent work in the general population separatingpast and current disorders has clarified that intoxication or withdrawal effectsdo not entirely account for the association,¹³ ashad been asserted earlier.^14-17 However,the nature of current or recent co-occurrence of substance and mood or anxietydisorders remains largely unexamined and poorly understood. Relative to lifetimedisorders, current co-occurrence has much more salience in its public healthand clinical implications. Thus, an important gap in knowledge about comorbidityremains.

One factor that has persistently hindered a better understanding ofthe relationship between substance use disorders and mood and anxiety disordersis diagnosis. The diagnosis of current mood or anxiety disorders among activesubstance abusers is complicated by the fact that many symptoms of intoxicationand withdrawal from alcohol and other substances resemble the symptoms ofmood and anxiety disorders. The diagnostic challenge among individuals withcurrent substance use disorders has been to devise diagnostic criteria andmeasurement techniques that differentiate between intoxication and withdrawalsymptoms and the symptoms of psychiatric disorders. This distinction is potentiallycrucial for etiologic research and treatment studies.

The DSM-IV¹⁸ representeda major departure from previous nomenclature in the importance placed on theindependent and substance-induced distinction and the clarity and specificityof the guidelines for making the distinction. Among individuals with substanceuse disorders, independent DSM-IV diagnoses of moodor anxiety disorders can be made 2 ways. First, the full mood or anxiety syndromeis established before substance use. Second, the mood or anxiety syndromepersists for more than 4 weeks after the cessation of intoxication or withdrawal.In contrast, substance-induced disorders are defined as those occurring onlyduring periods of substance use (or remitting shortly thereafter). These specificdiagnostic criteria provide a clearly defined situation for studying the associationof substance use disorders and mood and anxiety disorders that eliminatespotential diagnostic confusion arising from misdiagnosis of intoxication orwithdrawal effects.

There have been recent attempts to respond to the challenge of differentiatingindependent and substance-induced mood and anxiety disorders in clinical samples,focusing on patients with substance use disorders.^14-17 Thesedifferentiations were based on the occurrence of substance use disorders ratherthan on substance use per se. In these studies, independent mood or anxietydisorders were defined as episodes occurring either before the lifetime initialonset of a substance use disorder or during a period of remission lastingat least 3 months. Remission was defined as abstinence. Other episodes ofmood or anxiety disorders were classified as substance-induced disorders.The distinction between independent and substance-induced disorders in thesestudies is problematic in several ways. First, retrospective reports of chronologicalsequences occurring many years earlier may be inaccurate. Second, basing thedistinction on substance use disorders rather than on periods of substanceuse leaves open the possibility that independent psychiatric disorders occurringduring periods of nondiagnosable substance use were missed. Third, the clinicalassessment methods in these studies did not ascertain episodes of independentmood and anxiety disorders beginning during periods of drinking or drug useand persisting longer than 1 month after the cessation of use (as specifiedin DSM-IV), thus potentially missing further independentcases. From an epidemiologic perspective, however, the most serious problemwith research on comorbidity in treated samples is that the samples of subjectsdo not represent the underlying populations. Avoiding this problem requiresepidemiologic methods.

To our knowledge, no epidemiologic survey has used the DSM-IV definitions of independent and substance-induced disorders toinvestigate comorbidity between substance use disorders and mood and anxietydisorders. The Epidemiologic Catchment Area¹⁹ survey,conducted in the early 1980s, based its diagnoses on the DSM-III,²⁰ which had little relevanceto today's diagnostic concepts, in either the criteria for substance use disordersor the characterization of the independent and substance-induced distinction.The 1990-1992 National Comorbidity Survey (NCS)² used DSM-III-R²¹ criteria. Whilethe DSM-III-R definitions of substance use disorderswere more similar to those in the DSM-IV, the handlingof substance-induced disorders was quite different. The more recent 2001-2002NCS-2 and NCS-Replication²² were intended toyield DSM-IV diagnoses. However, the NCS-2 and NCS-Replicationassessment instruments did not differentiate between independent and substance-induceddisorders, but rather asked respondents if they thought their mood or anxietydisorder was due to drinking or drug use or to a physical illness. Clearly,such opinions may differ from the intent and the specific definitions providedin the DSM-IV.

In addition, measurement of substance use disorders itself has hinderedexamination of the independent and substance-induced distinction and its effecton the comorbidity between substance use disorders and mood and anxiety disordersin the general population. In the Epidemiologic Catchment Area survey²³ and the NCS,² substancedependence was not measured as a syndrome, because clustering in time of therequired number of symptoms was not assessed. In addition, the NCS-2 and NCS-Replicationdo not yield drug-specific diagnoses, but rather produce polysubstance dependencediagnoses for which dependence criteria are met for substances as a group,but not necessarily for any specific drug. In addition, the symptoms of abuseare used as screeners for dependence, with negative responses to abuse questionsleading to a skip past questions on dependence. This leads to an undercountof about one third of the cases of dependence in the general population.²⁴ However, more seriously, it leads to a loss of specifictypes of cases, because women with dependence are much less likely to havesymptoms of abuse than men.²⁴ Women are alsothe individuals most likely to have mood and anxiety disorders, so missingthese cases of dependence without abuse symptoms is likely to lead to underestimatesof prevalence and comorbidity.

Because of the widespread prevalence of mood, anxiety, and substanceuse disorders and their associated disabilities and social costs, an accurateunderstanding of their comorbidity is crucial to prevention and treatment.This report presents data from a major national survey designed to overcomethe problems of previous epidemiologic surveys on comorbidity. This survey,the National Institute on Alcohol Abuse and Alcoholism's National EpidemiologicSurvey on Alcohol and Related Conditions (NESARC),^25,26 coversthe comorbidity of DSM-IV substance use disordersand 9 independent mood and anxiety disorders in a nationally representativeUS sample of 43 093 respondents. To our knowledge, this is the largestcomorbidity survey ever conducted. The sample size allows for accurate estimationof current comorbidity and/or rare conditions. More important, to our knowledge,the NESARC is the first and only national survey to use the specific DSM-IV definitions of independent and substance-induceddisorders to determine if mood, anxiety, and substance use disorders are associatedeven when substance-induced disorders are ruled out. Furthermore, the NESARCoperationalized alcohol and drug dependence as syndromes, measured drug-specificdiagnoses of dependence, and ascertained alcohol and drug dependence amongall alcohol and drug users, regardless of whether they had an abuse diagnosis.The study also provides comorbidity rates separately for respondents seekingtreatment for alcohol, drug, and emotional problems because rates and patternsof comorbidity associated with the presenting complaint are most germane topracticing clinicians.

Wave 1 of the NESARC is a nationally representative face-to-face surveyof 43 093 respondents, 18 years and older, conducted by the NationalInstitute on Alcohol Abuse and Alcoholism in 2001-2002.^25,26 Thetarget population of the NESARC is the civilian noninstitutionalized populationresiding in the United States, including Alaska and Hawaii. The housing unitsampling frame of the NESARC was the US Bureau of the Census SupplementarySurvey.²⁵ The NESARC also included a groupquarters' sampling frame derived from the Census 2000 Group Quarters Inventory.²⁵ The group quarters' sampling frame captures importantsubgroups of the population with heavy substance use patterns not often includedin general population surveys. These included the military living off base,boarding houses, rooming houses, nontransient hotels and motels, shelters,facilities for housing workers, college quarters, and group homes. Hospitals,jails, and prisons were not among the group quarters sampled. The overallsurvey response rate was 81.0%, substantially higher than that of other surveysof this kind.

Black and Hispanic households were oversampled. The oversampling procedureincreased the percentage of non-Hispanic black households in the sample from12.3% to 19.1% (n = 8245) and the percentage of Hispanic households from 12.5%to 19.3% (n = 8308). Black and Hispanic persons were oversampled because thesesubgroups have been underrepresented in previous comorbidity surveys. Onesample person from each household or group quarters' unit was randomly selectedfor interview, and young adults, aged 18 to 24 years, were oversampled ata rate of 2.25 times that of other members in the household.

The NESARC sample was weighted to adjust for the probabilities of selectionof a sample housing unit or housing unit equivalent from the group quarters'sampling frame, nonresponse at the household and person levels, the selectionof 1 person per household, and oversampling of young adults. Once weighted,the data were adjusted to be representative of the US population for varioussociodemographic variables, including region, age, sex, race, and ethnicity,based on the 2000 Decennial Census. The sociodemographic distribution of theNESARC sample is shown in Table 1.

The diagnostic interview used to generate the diagnoses presented inthis report is the National Institute on Alcohol Abuse and Alcoholism AlcoholUse Disorder and Associated Disabilities Interview Schedule–DSM-IV Version (AUDADIS-IV),²⁷ a state-of-the-artstructured diagnostic interview designed for use by lay interviewers. The DSM-IV diagnoses reported herein, and included in the AUDADIS-IV,were alcohol and drug–specific abuse and dependence (excluding nicotinedependence), major depression, dysthymia, mania, hypomania, panic disorderwith and without agoraphobia, social phobia, specific phobia, and generalizedanxiety disorder. Not all mood and anxiety disorders were assessed in wave1 of the NESARC because of time and space constraints. However, wave 2 ofthe NESARC will assess posttraumatic stress disorder.

The AUDADIS-IV included an extensive list of symptom questions thatseparately operationalized DSM-IV criteria for substanceuse disorders, including alcohol abuse and dependence and drug–specificabuse and dependence for 8 classes of drugs, including sedatives, tranquilizers,opiates (other than heroin or methadone), stimulants, hallucinogens, cannabis,cocaine (including crack cocaine), and inhalants/solvents. Consistent withthe DSM-IV, 12-month (current) AUDADIS-IV diagnosesof alcohol abuse required a respondent to meet at least 1 of the 4 criteriadefined for abuse in the 12-month period preceding the interview. The AUDADIS-IVdependence diagnoses required the respondent to satisfy at least 3 of the7 DSM-IV criteria for dependence during the pastyear. The drug-specific diagnoses of abuse and dependence were derived usingthe same algorithm previously described for alcohol use disorders.

The test-retest reliabilities of AUDADIS-IV alcohol and drug disordermeasures were excellent, exceeding κ = 0.74 for alcohol diagnoses and κ= 0.79 for drug diagnoses.^28-32 Thediscriminant and convergent,^33-44 concurrent,^45,46 construct,^47-49 andpopulation⁵⁰ validity of the AUDADIS-IV alcoholand drug use disorder diagnoses also have been well documented, includingin the World Health Organization/National Institutes of Health Reliabilityand Validity Study.^{41,44,46,51-53}

Independent and substance-induced disorders were defined for respondentswho met the criteria for specific mood and anxiety disorder occurring duringthe past 12 months. Disorders were classified as independent if (1) the respondentabstained from alcohol and drug use in the past 12 months; (2) the episode(s)did not occur in the context of alcohol or drug intoxication or withdrawal;(3) the episode(s) occurred before alcohol or drug intoxication or withdrawal;or (4) the episode(s) began after alcohol or drug intoxication or withdrawal,but persisted for more than 1 month after the cessation of alcohol or drugintoxication or withdrawal. Substance-induced disorders were defined as episodesthat began after alcohol and/or drug intoxication and/or withdrawal, but either(1) were not associated with a period of at least 1 month of abstinence or(2) did not persist for more than 1 month after the cessation of alcohol ordrug intoxication or withdrawal.

Respondents were classified with a 12-month independent mood or anxietydisorder if none or only some of their episodes were substance induced. Respondentswere classified with a substance-induced disorder if all of their episodesin the past 12 months were substance induced.

The prevalence of major depression reported herein ruled out bereavement.All mood and anxiety disorders due to general medical conditions also wereruled out. The latter were defined as those occurring during the past 12 monthswhen the respondent was physically ill or recovering from being physicallyill, with the additional requirement that a physician or other health professionalconfirmed that the episode was related to the respondent's physical illnessor medical condition. This definition also required the onset of the moodor anxiety disorder to begin during the time of a physical illness or duringrecovery from it.

The test-retest reliabilities of AUDADIS-IV measures of DSM-IV mood and anxiety disorders were fair to good, ranging from κ= 0.42 for specific phobia to κ = 0.64 for major depression.^28,30 The validity of current mood andanxiety disorders was assessed in a series of linear regression analyses,using the NESARC data, that examined the associations between each mood andanxiety disorder and Short-Form-12v2⁵⁴ mentaldisability scores, controlling for age, personality disorders, current comorbidalcohol and drug use disorders, and all other comorbid mood and anxiety disorders.The Short-Form-12v2 is a reliable and valid measure of generic quality oflife used in large population surveys. In the present analyses, the focuswas on 4 Short-Form-12v2 mental disability scores (the mental component summaryscore, the social functioning score, the role emotional function score, andthe mental health score), reflecting general mental health functioning. Withthe exception of hypomania, all mood and anxiety disorders assessed in theNESARC were highly significant (P<.003-P<.001) predictors of the mental component summary, social functioning,role emotional, and mental health scores. Respondents with these current moodand anxiety disorders had significantly greater disability and social/occupationaldysfunction than respondents who did not have the particular mood or anxietydisorder. A diagnosis of hypomania was a significant predictor (P = .049) of the social functioning score.

The NESARC respondents were asked about 12-month treatment use separatelyfor alcohol, drugs, and each specific mood or anxiety disorder. Alcohol treatmentuse was defined as seeking help for alcohol problems in the 12 months precedingthe survey, at any of the following agencies or from any of the followinghealth professionals: human services, including family services or other socialservice agencies; emergency department or crisis center; alcohol specialtyservices, including alcohol or drug detoxification ward or clinic, outpatientclinic, outreach program, or day or partial patient programs; inpatient wardof a psychiatric or general hospital or community mental health facility;alcohol or drug rehabilitation program; halfway house; and visits to a physician,psychiatrist, psychologist, social worker, or other health professional. The12-month drug treatment use questions paralleled those of the alcohol treatmentuse questions, with the exception that methadone maintenance programs werealso included as drug specialty services.

Twelve-month treatment use was ascertained separately for each specificmood and anxiety disorder. Respondents were classified as receiving treatmentin the past 12 months if they: (1) visited a counselor, therapist, physician,psychologist, or person like that to get help for a mental disorder; (2) werea patient in a hospital for at least 1 night related to a mental disorder;(3) visited an emergency department to get help for a mental disorder; or(4) were prescribed medications for a mental disorder.

Approximately 1800 experienced lay interviewers from the US Census Bureauadministered the NESARC using laptop computer–assisted software thatincluded built-in skip, logic, and consistency checks. On average, the interviewershad 5 years of experience working on census and other health-related nationalsurveys. The interviewers completed 10 days of extensive training. This wasstandardized through centralized training sessions under the direction ofthe National Institute on Alcohol Abuse and Alcoholism and census headquartersstaff.

Regional supervisors recontacted a random 10% of all respondents forquality control purposes and for verification of the accuracy of the interviewer'sperformance. In addition, 2657 respondents were randomly selected to participatein a reinterview study after completion of their NESARC interview. These interviewsnot only served as an additional check on survey data quality but formed thebasis of a test-retest reliability study³⁰ ofAUDADIS-IV modules introduced in the NESARC.

Cross tabulations were used to calculate prevalences, comorbidity, and12-month treatment use for alcohol, drug, mood, and anxiety disorders. Oddsratios (ORs) were used to study associations between substance use disordersand independent mood and anxiety disorders. Standard errors and 95% confidenceintervals were estimated using a software package (SUDAAN⁵⁵)that uses Taylor series linearization to adjust for the design effects ofcomplex sample surveys like the NESARC.

The 12-month prevalences of independent mood and anxiety disorders were9.21% and 11.08% in the total sample, respectively (Table 2). The prevalences of substance-induced mood and anxietydisorders among respondents with any mood or anxiety disorder in the totalsample and among respondents with and without a current substance use disorderwere small, less than 1.0%. Of the approximately 19.3 million adults who hada current mood disorder, only 202 211 experienced episodes that wereclassified exclusively as substance induced. Similarly, among those with acurrent anxiety disorder (23.0 million), only a few (50 980) experiencedepisodes that were exclusively classified as substance induced. Of those respondentswho were classified as having at least 1 current independent mood or anxietydisorder, only 7.35% and 2.95%, respectively, reported experiencing independentand substance-induced episodes during the year preceding the survey.

The 12-month prevalences of any substance, any alcohol, and any druguse disorders were 9.35%, 8.46%, and 2.00%, respectively (Table 3). The rate of cannabis use disorder was 1.45%, far exceedingthe rates of other drug-specific use disorders (0.02% for inhalant/solventabuse to 0.35% for opioid use disorders). The rates for abuse exceeded thosefor dependence regardless of the specific substance use disorder examined.

The 12-month associations between substance use disorders and independentmood and anxiety disorders are shown in Table 4 in the form of ORs. The overall pattern of ORs is overwhelminglypositive, with 84.8% of the disorder-specific ORs positive (ie, >1.0) andstatistically significant. All independent mood and anxiety disorders werestrongly and consistently related to alcohol and drug use disorders (ORs,1.6-13.9). Any drug abuse also was significantly related to all independentmood and anxiety disorders (ORs, 1.6-4.2). The exception to the overall patternwas the level of association between alcohol abuse and specific independentmood and anxiety disorders, which was not always significant. All the independentmood and anxiety disorders were consistently more strongly related to alcoholand drug dependence than to drug abuse. Mania was more strongly related tothe substance use disorders (ORs, 1.4-13.9) than any other mood or anxietydisorder. Among the anxiety disorders, panic disorder with agoraphobia wasmost strongly associated with substance use disorders (ORs, 1.9-10.5).

As indicated by the entry in the upper left corner of Table 5, 19.67% of the respondents with any substance use disorderhad at least 1 independent mood disorder during the same 12-month period.Furthermore, 17.71% had at least 1 independent anxiety disorder. Among respondentswith any substance use disorder, 3.30% to 14.50% also had a specific mooddisorder and 1.46% to 10.54% had a specific anxiety disorder. These rateswere consistently lower for abuse than for dependence, and highest for anydrug dependence. Respondents with substance use disorders were more likelyto have major depression and specific phobia than any other mood or anxietydisorder.

Among respondents with any 12-month mood disorder, 19.97% had at least1 substance use disorder, and among those with any 12-month anxiety disorder,14.96% had at least 1 substance use disorder (Table 6). Among respondents with specific mood disorders, 18.07%to 27.91% also had at least 1 substance use disorder. This was also true of13.83% to 24.15% of the respondents with specific anxiety disorders. Prevalenceswere consistently lower for abuse than for dependence. Respondents with panicdisorder with agoraphobia and generalized anxiety disorder were more likelythan those with other mood and anxiety disorders to have a substance use disorder.

The percentage of respondents with at least one 12-month independentmood disorder who sought treatment in the past 12 months was 25.81%, whilethe corresponding percentage for respondents with at least 1 independent anxietydisorder was 12.13% (Table 7).Treatment use was greater for those with dysthymia, major depression, andmania than for those with hypomania. Among respondents with anxiety disorders,treatment use was greater for those with panic disorder, with and withoutagoraphobia, and generalized anxiety disorder than for those with social andspecific phobias. Among respondents reporting specific independent mood disorders,between 18.54% and 30.97% had a comorbid substance use disorder, primarilyan alcohol use disorder. Among respondents reporting specific independentanxiety disorders who sought treatment, 15.38% to 21.89% had a comorbid substanceuse disorder, again primarily an alcohol use disorder.

Only 5.81% and 13.10% of respondents who had a 12-month alcohol usedisorder or a 12-month drug use disorder, respectively, sought treatment fortheir particular substance use disorder during that same period (Table 8). Among those who sought treatmentfor an alcohol use disorder, 40.69%, 33.38%, and 33.05% had at least 1 independentmood disorder, independent anxiety disorder, or drug use disorder, respectively.Among respondents with any drug use disorder who sought treatment for thatdisorder, 60.31% had at least 1 independent mood disorder, 42.63% had at least1 independent anxiety disorder, and 55.16% had a comorbid alcohol use disorder.

The major findings of this study document the extremely high rates ofsubstance use disorders and independent mood and anxiety disorders in theUS population, and confirm the strength of associations between them. Theprevalence of any current independent mood disorder was 9.21%, representing19.2 million adult Americans. The prevalence of any current independent anxietydisorder was slightly higher, 11.08%, representing 23.0 million US adults.The rate of any current substance use disorder was only slightly greater thanthat estimated for independent mood disorders, 9.35%, representing 19.4 millionUS adults. Almost 9% (17.6 million adult Americans) had an alcohol use disorder,while 2% (4.2 million adult Americans) had a drug use disorder. Furthermore,about 20% of all persons in the general population with a current substanceuse disorder had at least 1 current independent mood disorder and 18% hadat least 1 current independent anxiety disorder. Similarly, about 20% of theindividuals with at least 1 current independent mood disorder had a comorbidsubstance use disorder, while about 15% of the individuals with at least one12-month independent anxiety disorder had a substance use disorder. More important,this study also demonstrated that a few individuals in the general populationexperienced current mood (202 211 adult Americans) or anxiety (50 980adult Americans) disorders that were only substance induced.

Of considerable clinical relevance is the finding that 40.7% of theindividuals with a current alcohol use disorder who sought treatment duringthe same period had at least 1 current independent mood disorder, while morethan 33% had at least 1 current independent anxiety disorder. Among individualswith a current drug use disorder who sought treatment, about 60% and 43% hadat least 1 current independent mood or anxiety disorder, respectively. Similarly,among individuals with at least 1 current independent mood or anxiety disorderwho sought treatment, about 20% and 16%, respectively, had a current substanceuse disorder that was more likely to be an alcohol than a drug use disorder.This suggests that the predominance of substance-induced (approximately 60%)rather than independent mood or anxiety disorders found in several recentclinical studies^15-17 ofsubstance abusers was most likely due to diagnostic methods that do not entirelyconform to the DSM-IV guidelines for differentiatingindependent from substance-induced disorders. Regardless of the relative prevalenceof independent and substance-induced disorders, however, substance-inducedmood or anxiety disorders among individuals with substance use disorders areserious conditions. For example, when diagnosed carefully according to DSM-IV guidelines, substance-induced disorders have beenshown to increase the risk for poor outcome of substance dependence⁵⁶ and lifetime number of suicide attempts.⁵⁷ Additional longitudinal research is needed to examinedifferences in the course and prognosis of chronic substance-induced disordersand independent mood and anxiety disorders in treated samples.

Taken together, the NESARC results provide clear and persuasive evidencethat mood and anxiety disorders must be addressed by alcohol and drug treatmentspecialists and that substance use disorders must be addressed by primarycare physicians and mental health treatment specialists. These results highlightthe need for all individuals in treatment to be fully assessed for the presenceor absence of a range of psychiatric disorders. Furthermore, the results underscorethe importance of past and ongoing development of improved treatments forthose individuals meeting the criteria for 2 or more disorders.^58-62 Moreover,these results strongly suggest that treatment for a mood or anxiety disordershould not be withheld from those with substance use disorders in stable remissionon the assumption that most of these disorders are due to intoxication orwithdrawal. Left untreated, such mood disorders have been shown to lead torelapse of substance dependence⁵⁶ and can alsobe fatal, as many former substance abusers with severe untreated independentdepression will die by suicide. Short of this ultimately adverse outcome,independent mood and anxiety disorders, particularly among individuals whohave a comorbid substance use disorder, are immensely disabling.^4-7

From an etiologic perspective, this study does not resolve questionsregarding the casual mechanisms underlying the relationship between DSM-IV substance use disorders and independent mood andanxiety disorders. Prospective surveys have great potential to inform us aboutprocesses associated with comorbidity and will provide the vehicles for examiningthe sequencing of comorbid disorder onset. The NESARC was designed with thisparadigm in mind, and its second wave will be fielded in 2004-2005.

Correspondence: Bridget F. Grant, PhD, PhD, Laboratory of Epidemiologyand Biometry, Division of Intramural Clinical and Biological Research, NationalInstitute on Alcohol Abuse and Alcoholism, National Institutes of Health,Mail Stop 9304, 5635 Fishers Ln, Room 3077, Bethesda, MD 20892-9304 (bgrant@willco.niaaa.nih.gov).

Submitted for publication November 12, 2003; final revision receivedFebruary 6, 2004; accepted February 13, 2004.

The NESARC is supported by the National Institute on Alcohol Abuse andAlcoholism, Bethesda, Md, with supplemental support from the National Instituteon Drug Abuse, Bethesda.

We thank the more than 1800 US Census Bureau field representatives whoadministered the NESARC interview for their hard work, dedication, and professionalism.

The views and opinions expressed in this article are those of the authorsand should not be construed to represent the views of any of the sponsoringorganizations, agencies, or the US government.