PubMed2002
The bipolar II spectrum represents the most common phenotype of bipolarity. Numerous studies indicate that in clinical settings this soft spectrum might be as common--if not more common than--major depressive disorders. The proportion of depressive patients who can be classified as bipolar II further increases if the 4-day threshold for hypomania proposed by the DSM-IV is reconsidered. The modal duration of hypomanic episodes is 2 days; highly recurrent brief hypomania is as short as 1 day, and when complicated by major depression, it should be classified as a variant of bipolar II. Another variant of the bipolar II pattern is represented by major depressive episodes superimposed on cyclothymic or hyperthymic temperamental characteristics. The literature is unanimous in supporting the idea that depressed patients who experience hypomania during antidepressant treatment belong to the bipolar II spectrum. So-called alcohol- or substance-induced mood disorders may have much in common with bipolar II spectrum disorders, in particular when mood swings outlast detoxification. Finally, many patients within the bipolar II spectrum, especially when recurrence is high and the interepisodic period is not free of affective manifestations, may meet criteria for personality disorders. This is particularly true for cyclothymic bipolar II patients, who are often misclassified as borderline personality disorder because of their extreme mood instability. Subthreshold mood lability of a cyclothymic nature seems to be the common thread that links the soft bipolar spectrum. The authors submit this to represent the endophenotype likely to be informative in genetic investigations. Mood lability can be considered the core characteristics of the bipolar II spectrum, and it has been validated prospectively as a sensitive and specific predictor of bipolar II outcome in major depressives. In a more hypothetical vein, cyclothymic-anxious-sensitive temperamental disposition might represent the mediating underlying characteristic in the complex pattern of anxiety, mood, and impulsive disorders that bipolar II spectrum patients display throughout much of their lifetimes. The foregoing conclusions, based on clinical experience and the research literature, challenge several conventions in the formal classificatory system (i.e., ICD-10 and DSM-IV). The authors submit that the enlargement of classical bipolar II disorders to include a spectrum of conditions subsumed by a cyclothymic-anxious-sensitive disposition, with mood reactivity and interpersonal sensitivity, and ranging from mood, anxiety, impulse control, and eating disorders, will greatly enhance clinical practice and research endeavors. Prospective studies with the requisite methodologic sophistication are needed to clarify further the relationship of the putative temperamental and developmental variables to the complex syndromic patterns described herein. The authors believe that viewing these constructs as related entities with a common temperamental diathesis will make patients in this realm more accessible to pharmacologic and psychological approaches geared to their common temperamental attributes. The authors submit that the use of the term "spectrum" is distinct from a simple continuum of subthreshold and threshold cases. The underlying temperamental dimensions postulated by the authors define the disposition for soft bipolarity and its variation and dysregulation in anxious disorders and dyscontrol in appetitive, mental, and behavioral disorders, much beyond affective disorders in the narrow sense.