Show Summary Details
Page of

Prevalence and Severity of Psychiatric Comorbidities: The National Comorbidity Survey Replication (NCS-R) 

Prevalence and Severity of Psychiatric Comorbidities: The National Comorbidity Survey Replication (NCS-R)
Prevalence and Severity of Psychiatric Comorbidities: The National Comorbidity Survey Replication (NCS-R)

Stephanie Yarnell

, and Ellen Edens

Page of

PRINTED FROM OXFORD MEDICINE ONLINE ( © Oxford University Press, 2016. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy and Legal Notice).

Subscriber: null; date: 23 October 2019

Although mental disorders are widespread, serious cases are concentrated among a relatively small proportion of cases with high comorbidity.

Kessler et al.1

Research Question:

What is the prevalence and severity of comorbid anxiety, mood, impulse control, and substance use disorders?


National Institute of Mental Health and the National Institute on Drug Abuse

Year Study Began:


Year Study Published:


Study Location:

Household survey based in the United States

Who Was Studied:

English speaking adults aged 18 years and older

Who Was Excluded:

Non-English speakers, anyone under 18 years of age, institutionalized persons, and homeless individuals (non-household)

How Many Participants:

9,282 in first wave of interviews; 5,692 in second wave

Study Overview:

See Figure 20.1 for a summary of the study design.

Study Design:

Participants underwent a structured lay-administered interview using the international World Health Organization–Composite International Diagnostic Interview (WHO-CIDI) evaluating for the presence of DSM-IV anxiety, mood, impulse control, and substance use disorders. While the analysis was limited to adults, participants were screened for childhood diseases through recall-questioning. Mental health issues or comorbidities of late life were not assessed.

If a DSM-IV diagnosis was present, participants were asked to perform dimensional self-ratings to assess risk factors, severity, and perceived impairment. Subsequently, participants were reinterviewed using the Shahan Disability Scale to assess level of functional impairment and severity.




Presence of anxiety, mood, impulse control, or substance use disorders by interview


  • Of those with diagnosable conditions in the 12 months prior to interview, 55% had a single diagnosis; 45% had two or more co-occurring psychiatric diagnoses.

  • The median age of onset for lifetime mental disorder was 14 years. Anxiety (11 years) and impulse control (11 years) disorders present earlier in life; substance use (20 years) and mood (30 years) disorders emerge later. Across diagnoses, three fourths had onset of disease by age 24.

  • Approximately one fourth (22.3%) of all 12-month cases were deemed to be severe in nature, while the majority (40.4%) were mild (Table 20.1).

Table 20.1 Summary of the NCS-R’s Key Findings


Anxiety Disorders

Mood Disorders

Impulse Control Disorders

Substance Use Disorders

Any MH Disorder

12-month prevalence (SE)

18.1% (0.7)

9.5% (0.4)

8.9% (0.5)

3.8% (0.3)

26.2% (0.3)

Lifetime prevalence (SE)

28.8% (0.9)

20.8% (0.6)

24.8% (1.1)

14.6% (0.6)

46.4% (1.1)

Notes: NCS-R = National Comorbidity Survey Replication. MH = mental health.

Criticisms and Limitations:

The study has several notable limitations regarding inclusion. First, homeless individuals, those in institutions, and non-English speakers were excluded from the analysis, limiting the generalizability of the findings to these populations and ability to make cultural inferences. Moreover, the results may have been impacted by selection bias as the response rate was only 70.9%, and those with mental illness may have been reluctant to participate. Even among those who agreed to be interviewed, a potential reporting bias may exist since mental illness remains stigmatized and unfamiliar to many people and, as a consequence, is commonly underreported.

Additionally, the study only evaluated for a limited number of conditions; it did not include primary psychotic, cognitive, eating, or personality disorders. Finally, interviews were conducted by laypersons (“professional interviewers” from a Social Research Department) and not clinicians trained in the treatment of mental illness, thus introducing the possibility of missed or incorrect diagnoses.

Other Relevant Studies and Information:

  • Other relevant studies include the Epidemiological Catchment Area study,2 the original National Comorbidity Study (NCS),3 the National Epidemiologic Survey on Alcohol and Related Conditions,4 and the National Comorbidity Study–Adolescents (NCS-A).

  • In 2001 – 2002, respondents of the baseline NCS were reinterviewed (NCS-2) in a follow-up study to evaluate patterns and predictors of mental health and substance use disorders.5

Summary and Implications:

The NCS (done in the early 1990’s) was the first nationally representative mental health epidemiological study to use a structured diagnostic interview to estimate the prevalence and correlates of mental disorders. The NCS-R, completed in 2005, was a replication survey conducted between 2001 and 2003, with analysis of time trends and expanded the assessment of certain diseases. The findings of the NCS-R showed that past year prevalence rates for anxiety, mood, impulse control, or substance use disorders within the United States are high with anxiety and mood disorders being the most common. The lifetime prevalence of mental health disorders including anxiety, mood, impulse control, or substance use disorders within the United States approach 50%, while the 12-month prevalence is approximately 25%.

Additionally, a substantial percentage, 14% of the population, suffer from symptoms in the moderate to severe range. A very substantial minority of people with past-year diagnosis (40%) had another, co-occurring mental health disorder; the severity of disease was strongly correlated with comorbidity. These results suggest that while the majority of cases of anxiety, mood, impulse control, or substance use disorders are mild, they remain highly prevalent in the population. Those suffering from moderate to severe disease are at increased likelihood of having two or more mental health diagnoses compared to those with mild disease.

Clinical Case: Prevalence and Severity of Psychiatric Comorbidities

Case History

A 38-year-old mother of two comes into an outpatient psychiatrist’s office complaining of severe anxiety. She is afraid to speak with anyone about it and has become very isolative in the wake of these symptoms. Her husband is concerned that she is becoming depressed as a result of impairments brought on by her anxiety. They want to know if this is possible and if there is help available.

Suggested Answer

According to the results of the NCS-R, anxiety is the most common mental disorder in the United States, with approximately 20% of the population meeting DSM-IV criteria for an anxiety disorder in any 12-month period. Co-occurrence of mental illness (i.e., having more than one diagnosable condition at a time) is common. Indeed, approximately 45% of individuals suffer from two or more co-occurring conditions; rates are higher in persons diagnosed with severe impairments. Given this, it is likely she has developed a second diagnosis in the wake of severe anxiety. Anxiety and depression are the two most common mental health disorders, and both are treatable.


1. Kessler, R. C., Chiu, W. T., Demler, O., & Walters, E. E. (2005). Prevalence, severity, and comorbidity of twelve-month DSM-IV disorders in the National Comorbidity Survey Replication (NCS-R). Archives of General Psychiatry, 62(6), 617–627.Find this resource:

2. Regier, D. A., Myers, J. K., Kramer, M., Robins, L. N., Blazer, D. G., Hough, R. L., . . . Locke, B. Z. (1984). The NIMH Epidemiologic Catchment Area program: Historical context, major objectives, and study population characteristics. Archives of General Psychiatry, 41(10), 934–941.Find this resource:

3. Kessler, R. C., McGonagle, K. A., Zhao, S., Nelson, C. B., Hughes, M., Eshleman, S., . . . Kindler, K. S. (1994). Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States: Results from the National Comorbidity Survey. Archives of General Psychiatry, 51(1), 8–19.Find this resource:

4. Grant, B. F., Stinson, F. S., Dawson, D. A., Chou, S. P., Ruan, W. J., & Pickering, R. P. (2003). Source and accuracy statement: Wave 1 national epidemiologic survey on alcohol and related conditions (NESARC). Bethesda, MD: National Institute on Alcohol Abuse and Alcoholism.Find this resource:

    5. Kessler, R. (2015). National Comorbidity Survey: Reinterview (NCS-2), 2001–2002. Ann Arbor, MI: Inter-university Consortium for Political and Social Research.Find this resource: