Research report
The prevalence and disability of bipolar spectrum disorders in the US population: re-analysis of the ECA database taking into account subthreshold cases

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Abstract

Background: Despite emerging international consensus on the high prevalence of the bipolar spectrum in both clinical and community samples, many skeptics contend that narrowly defined bipolar disorder with a lifetime rate of about 1% represents a more accurate estimate of prevalence. This may in part be due to the fact that higher figures proposed for the bipolar spectrum (5–8%) have not been based on national data and have not included all levels of manic symptom severity. In the present secondary analyses of the US National Epidemiological Catchment Area (ECA) database, we provide further clarification on this fundamental public health issue. Methods: All respondents in the first wave (first interview) of the ECA household five site sample (n=18,252) were classified on the basis of DSM-III criteria into lifetime manic and hypomanic episodes, as well as those with at least two lifetime manic/hypomanic symptoms below the threshold for at least 1 week duration (subsyndromal manic symptoms [SSM] group). Odds ratios were calculated on lifetime service utilization for mental health problems, measures of adverse psychosocial outcome, and suicidal behavior compared to subjects with no mental disorders or manic symptoms. Results: As originally reported nearly two decades ago by the primary investigators of the ECA, the lifetime prevalence for manic episode was 0.8%, and for hypomania, 0.5%. What is new here is the inclusion of subthreshold SSM subjects, which accounted for 5.1%, yielding a total of 6.4% lifetime prevalence for the bipolar spectrum. All three (manic, hypomanic and SSM) groups had greater marital disruption. There were significant increases in lifetime health service utilization, need for welfare and disability benefits and suicidal behavior when the SSM, hypomanic and manic subjects were compared to the no mental disorder group. Suicidal behavior was non-significantly highest in the hypomanic (bipolar II) group. Otherwise, hypomanic and manic groups had comparable level of service utilization and social disruption. Limitations: Comorbid disorders, which might influence functioning, were not included in the present analyses. Conclusion: These secondary analyses of the US National ECA database provide convincing evidence for the high prevalence of a spectrum of bipolarity in the community at 6.4%, and indicate that subthreshold cases are at least five times more prevalent than DSM-based core syndromal diagnoses at about 1%. These SSM subjects, who met the criteria of “caseness” from the point of view of harmful dysfunction, are of great theoretical and public health significance.

Introduction

There is increasing international consensus based on a review of the evidence-based literature that bipolarity involves more than classical bipolar I disorder, that indeed its most common manifestations involve bipolar II and softer hypomanic expressions with various admixtures of depression (summarized in Akiskal et al., 2000, Akiskal, 2002). The current estimates place the community prevalence of the bipolar spectrum at a minimum of 5% (Lewinsohn et al., 1995; Angst, 1998; Szadoczky et al., 1998). The concept of the spectrum and its high prevalence has been greeted with skepticism on methodologic grounds (Baldessarini, 2000; Soares and Gershon, 2000), and a plea has been made to limit bipolarity to narrowly defined bipolar I and bipolar II. The conventional, usually cited, rates of 1%, based on the US Epidemiologic Catchment Area or ECA database (Regier et al., 1984, 1994) and 1.6% from the National Comorbidity Study or NCS (Kessler et al., 1994) are usually invoked to justify the relative “rarity” of bipolarity. Given the fact that the higher estimates placing bipolarity 3–5 times higher than the conventional rates do not derive from national data (Lewinsohn et al., 1995; Angst, 1998; Szadoczky et al., 1998), we felt that national data were needed to sway the skeptics. Accordingly, we have conducted what we believe to be the first analyses—deriving from the US National ECA database—on both manic/hypomanic and subsyndromal manic/hypomanic symptoms.

Bipolar disorder is a serious illness of major public health importance, which creates havoc and suffering in the afflicted as well as their families and loved ones. As such there is a need to determine accurately the full extent that bipolar illness is present in the general population and the degree of psychosocial impairment associated with it. In addition, prior attempts to examine psychosocial outcomes in bipolar disorder have largely dealt with such variables as chronicity and suicide in follow-up studies (Coryell et al., 1998, Angst and Preisig, 1995), but a detailed analysis of psychosocial dysfunction in a national cohort of bipolarity and its spectrum has not yet been conducted.

Recently, our research group (Judd et al., 2002, Judd et al., in press a, Judd et al., 2003, Judd et al., in press b) has reported a series of investigations focusing on the long-term symptomatic status of a large clinical cohort of bipolar I and bipolar II patients being followed by the NIMH Collaborative Depression Study (Katz and Klerman, 1979, Katz et al., 1979). We found that bipolar patients were symptomatically ill from these illnesses approximately half the time during long-term follow-up. Their symptom status frequently fluctuated and shifted in both polarity and severity. The longitudinal symptomatic course of bipolar patients was dominated, on a 3:1 basis, by moderate and subsyndromal affective symptoms compared with the syndromal level of manic and major depressive episodes; in the aggregate, these data support the conclusion that the longitudinal symptomatic expression of bipolar disorders is dimensional rather than categorical in nature, which means that when any level of affective symptoms are observed in bipolar patients it indicates that the bipolar illness is present and active.

What about nonclinical samples? We contend that to report lifetime prevalence of manic symptoms by focusing only on manic and/or hypomanic symptoms without including the prevalence of the subsyndromal manic/hypomanic symptoms, underestimates the true prevalence of the bipolar diathesis and spectrum. To test this hypothesis we conducted secondary analyses on the ECA household sample, predicting the following: (1) lifetime prevalence of subsyndromal, hypomanic, and manic symptoms in the aggregate, will exceed that which has been reported previously from the same database for the general population, (2) each level of bipolar symptom severity, even subsyndromal manic/hypomanic symptoms, will be associated with significantly increased lifetime health service use, need for welfare and disability benefits and suicidal behavior compared to subjects with no mental disorders or manic symptoms.

Section snippets

Subjects

The analysis sample is derived from the five data collection sites of the NIMH Epidemiologic Catchment Area Program (Baltimore, MD, Durham, NC, Los Angeles, CA, New Haven, CT, and St. Louis, MO). Sampling methodology, human subject consent procedures, study design, survey methods, demographic characteristics and prevalence of mental disorders of the sample have been described in detail in other reports (Eaton et al., 1984, Regier et al., 1984, Regier et al., 1994, Eaton and Kessler, 1985).

Lifetime prevalence

The lifetime prevalence of manic symptoms in the ECA household sample is shown in Table 1. The lifetime prevalence of manic symptoms in the general population totals 6.4%, with the vast majority of symptoms in the subthreshold (SSM) category at 5.1%, compared to 0.8% for manic episode, and 0.5% for hypomanic episode. (The respective rates of 0.8 and 0.5% are the same as reported in earlier ECA publications (Regier et al., 1984, Regier et al., 1994) and refer to DSM-III diagnosis for bipolar I

Prevalence of bipolarity in the community

Two studies, one based on community subjects in the Zurich canton (Angst, 1998) and the other based on patients in general medical practice in Hungary (Szadoscky et al., 1998) have reported, respectively, lifetime rates of 5.5% (DMS-IV) and 5.1% (DSM-III-R) for bipolar disorder; the Lewisohn et al. study (1995) in Oregon, USA, conducted on juvenile community subjects, reported a rate of 5.5%. The present analyses, reporting a lifetime prevalence of 6.4% (DSM-III), have the virtue of deriving

Conclusions

The following are the conclusions that can be drawn from these analyses: (1) the lifetime prevalence of subthreshold hypomanic/manic symptoms is substantially higher than that based only on manic or hypomanic episodes. (2) The structure of bipolar disorder in the population appears to be dimensional in nature and as such, all levels of manic spectrum severity present in the population should be included in estimating the true prevalence of bipolarity in the general population. (3) Lifetime

Acknowledgements

The authors would like to thank Pamela Schettler, Ph.D., for her critical comment of this manuscript, and Hillary Slade for her invaluable help in the preparation of this manuscript. This work was supported by the Roher Fund of the University of California, San Diego, CA, USA.

References (37)

  • H.S. Akiskal et al.

    Re-evaluating the prevalence of and diagnostic composition within the broad clinical spectrum of bipolar disorders

    J. Affect. Disord.

    (2000)
  • H.S. Akiskal

    Classification, diagnosis and boundaries of bipolar disorders

  • Diagnostic Statistical Manual of Mental Disorders

    (1980)
  • Diagnostic Statistical Manual of Mental Disorders

    (1994)
  • J. Angst et al.

    Outcome of a clinical cohort of unipolar, bipolar and schizoaffective patients. Results of a prospective study from 1959 to 1985

    Schweiz. Arch. Neurol. Psychiatry

    (1995)
  • R.J. Baldessarini

    A plea for integrity of the bipolar disorder concept

    Bipolar Disord.

    (2000)
  • R.A. Depue et al.

    A behavioral paradigm for identifying persons at risk for bipolar depressive disorder: a conceptual framework and five validation studies. (Monograph)

    J. Abnorm. Psychol.

    (1981)
  • D.L. Dunner et al.

    Heritable factors in the severity of affective illness

    Biol. Psychiatry

    (1976)
  • Cited by (0)

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