Research reportDifferences between bipolar I and bipolar II disorders in clinical features, comorbidity, and family history
Introduction
Bipolar disorder (BPD) is a polymorphous condition, with diverse clinical features and courses. In order to determine a more homogeneous subgroup, various clinical sub-diagnoses have been proposed (Akiskal and Pinto, 1999). Among them, bipolar I disorder (BP-I) and bipolar II disorder (BP-II) are the most well-established disorders to have been adopted as separate diagnoses in the DSM-IV classification (American Psychiatric Association, 1994). According to the DSM-IV, BP-I and BP-II are distinguished only by the presence of a manic or hypomanic episode. Criteria for mania and hypomania have the same symptom profile (apart from psychotic symptoms, that can occur in mania alone) and differ only in the degree of severity. For these reasons, nosological issues regarding the separation of BP-II from BP-I has been raised (Ghaemi et al., 2008). However, whether BP-I and BP-II differ only in the severity of manic-side episodes or in other clinically and biologically meaningful ways remains controversial (Brugue et al., 2008).
Based on family study, Gershon et al. (1982) proposed that all forms of BPD were best conceptualized as a spectrum of illness representing thresholds on a continuum of underlying vulnerability, i.e., schizoaffective > BP-I > BP-II > unipolar disorder. However, in other genetic epidemiologic studies, morbid risk of BP-II was shown to be much higher in relatives of BP-II probands than in those of BP-I probands, suggesting a somewhat different genetic liability between them (Coryell et al., 1984, Endicott et al., 1985, Andreasen et al., 1987, Heun and Maier, 1993). Further controversial results relate to clinical features and comorbidity. According to comparative studies, BP-II appears to develop less severe symptoms, but exhibits more of a chronic course with more frequent episodes (Vieta et al., 1997, Judd et al., 2003a). Moreover, unstable interpersonal relationships and social adjustment (Akiskal et al., 2006b), and comorbidity of psychiatric illness were more frequently observed in BP-II than in BP-I (Vieta et al., 2000, Mantere et al., 2006). A higher risk of suicide has also been reported in patients with BP-II as compared to those with BP-I (Arato et al., 1988, Rihmer and Pestality, 1999, Valtonen et al., 2008). In the evaluation of long-term diagnostic stability, only a small portion of BP-II was converted to BP-I, i.e., 5% in 5 years (Joyce et al., 2004) and 7.5% in 10 years (Coryell et al., 1995). However, some other study findings have been opposed to the distinction between BP-I and BP-II reporting similar rates of suicidal attempt, rapid cycling, seasonality, and comorbid psychiatric illness in both (Vieta et al., 1997, Valtonen et al., 2005).
The present study was designed to provide a comparison of BP-I and BP-II with respect to comprehensive clinical aspects based on information available in ordinary clinical settings, i.e., the clinical characteristics, prior course, patterns of axis I comorbidity, and family history. Cumulative data on the relationship between BP-I and BP-II could provide important clues for validation of the classification system of mood disorders. Furthermore, given that the criteria for subdividing manic and hypomanic episodes have been quite arbitrary and ambiguous, identification of further clinical characteristics that could be considered in the differential diagnosis between BP-I and BP-II in ordinary clinical settings is warranted.
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Subjects
Patients who met the diagnostic criteria of the DSM-IV BP-I and BP-II were recruited from outpatient and inpatient units of the Samsung Medical Center between September 2007 and January 2010. The best-estimate diagnosis was independently rendered for each individual by two psychiatrists. The age range was limited between 18 and 60 years and subjects had been required to be cliniclly stable, i.e., to have scored 3 (mildly ill) or lower on the Clinical Global Impression of Severity scale (Guy, 1976
Sociodemographic characteristics and clinical course
Table 1 shows the sociodemographic characteristics of 71 BP-I and 34 BP-II patients as well as 374 first-degree relatives of 57 BP-I and 31 BP-II patients. No significant difference between the subject groups was detected with respect to any of the sociodemographic variable investigated.
A comparison of the clinical course between BP-I and BP-II patients has been summarized in Table 2. There were no statistically significant differences in the age at onset of mood episode, (hypo)manic/mixed
Discussion
In relation to the nosological issue of separating BP-II from BP-I, the present study was designed to provide a comparison between BP-I and BP-II with respect to comprehensive clinical aspects based on information available in ordinary clinical settings, i.e., the clinical characteristics, prior course, patterns of axis I comorbidity, and family history.
In this study, BP-II patients experienced more frequent major depressive episodes than those with BP-I, which is consistent with results from
Conclusions
The present study provided a comparison between BP-I and BP-II with respect to comprehensive clinical aspects based on information available in ordinary clinical settings. The authors found significant differences in prior clinical course, symptomatology of depressive and manic episodes, axis I comorbidity, and family history of psychiatric problems between the two groups. In terms of severity of illness, BP-I showed more extensive manic symptoms; however, BP-II exhibited more serious and
Role of funding source
Funding for this study was provided by grants from the Korea Healthcare Technology R&D Project, Ministry for Health, Welfare & Family Affairs, Republic of Korea (A090096-0911-0000100) and the IN-SUNG Foundation for Medical Research. These two sponsors had no further role in study design; in the collection, analysis, and interpretation of data; in the writing of this report; or in the decision to submit the paper for publication.
Conflict of interest
No conflict declared.
Acknowledgement
This study was supported by the Korea Healthcare Technology R&D Project, Ministry for Health, Welfare & Family Affairs, Republic ofKorea (A090096-0911-0000100) and the IN-SUNG Foundation for Medical Research.
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2022, Asian Journal of PsychiatryCitation Excerpt :Bipolar disorder is an affective disorder associated with characteristic cognitive, physical, and behavioral symptoms that impair a patient's social functioning and are characterized by repeated changes in activity or energy (Clemente et al., 2015; Grande et al., 2016; World Health Organization, 1992). Bipolar disorder can be classified into bipolar I disorder (BD-I) and bipolar II disorder (BD-II) according to the severity of mood elevation (Grande et al., 2016; Harrison et al., 2016; Baek et al., 2011; Vieta et al., 1997). In the Diagnostic & Statistical Manual of Mental Disorders 5th edition (DSM-5), the diagnostic criteria for BD-I are depressive and manic episodes, and those for BD-II are hypomanic episodes and depressive episodes (American Psychiatric Association, 2013).
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Present address: Department of Psychiatry, Seoul National Hospital, Seoul, Republic of Korea.