Bipolar Disorder: Epidemiology

and are classified as separate illnesses. Some researchers increasingly view them as part of an overlapping spectrum that also includes anxiety and psychosis.

According to Hagop Akiskal, M.D., at the one end of the spectrum is type schizoaffective disorder, and at the other end is unipolar depression (recurrent or not recurrent), with the present across the spectrum. Also included in this view is premenstrual , postpartum depression, and . This view helps to explain why many people who have the illness do not have first-degree relatives with clear-cut “”, but who have family members with a history of these other disorders.

In a 2003 study, Hagop Akiskal M.D. and Lew Judd M.D. re-examined data from the landmark Epidemiologic Catchment Area study from two decades before.[43] The original study found that 0.8 percent of the population surveyed had experienced a manic episode at least once (the diagnostic threshold for I) and 0.5 a (the diagnostic threshold for II).

By tabulating to include sub-threshold , such as one or two symptoms over a short time-period, the authors arrived at an additional 5.1 percent of the population, adding up to a total of 6.4 percent of the entire population who can be thought of as having a . This and similar recent studies have been interpreted by some prominent disorders researchers as evidence for a much higher prevalence of conditions in the general population than previously thought.

However these re-analyses should be interpreted cautiously because of substantive as well as limitations. Indeed, of are carried out by lay interviewers (that is, not by expert clinicians/psychiatrists who are more costly to employ) who follow fully structured/fixed interview schemes; responses to single items from such interviews may suffer limited validity.

Furthermore, a well-known statistical problem arises when ascertaining disorders and conditions with a relatively low population prevalence or base-rate, such as : even assuming that lay interviews diagnoses are highly accurate in terms of sensitivity and specificity and their corresponding area under the ROC curve (that is, AUC, or area under the receiver operating characteristic curve), a condition with a relatively low prevalence or base-rate is bound to yield high false positive rates, which exceed false negative rates; in such a circumstance a limited positive predictive value, PPV, yields high false positive rates even in presence of a specificity which is very close to 100%.[44] To simplify, it can be said that a very small error applied over a very large number of individuals (that is, those who are *not affected* by the condition in the general population during their lifetime; for example, over 95%) produces a relevant, non-negligible number of subjects who are incorrectly classified as having the condition or any other condition which is the object of a survey study: these subjects are the so-called false positives; such reasoning applies to the ‘false positive’ but not the ‘false negative’ problem where we have an error applied over a relatively very small number of individuals to begin with (that is, those who are *affected* by the condition in the general population; for example, less than 5%). Hence, a very high percentage of subjects who seem to have a history of at the interview are false positives for such a medical condition and apparently never suffered a fully clinical syndrome (that is, type I): the population prevalence of type I, which includes at least a lifetime manic episode, continues to be estimated at 1%.[45] “Mild-to-severe versions of afflict nearly 4 percent of adults at some time in their lives.”[46]

A different but related problem in evaluating the public health significance of psychiatric conditions has been highlighted by Robert Spitzer of Columbia University: fulfillment of and the resulting diagnosis do not necessarily imply need for treatment.[47] As a consequence, subjects who experience symptoms but not a full-blown, impairing syndrome should not be automatically considered as patients in need of treatment.

Recent studies have indicated that at least 50% of adult sufferers report manifestation of symptoms before the age of 17. Moreover, there is a growing consensus that originates in childhood. In young children the illness is now referred to as pediatric . Today about 0.5% of children under 18 are believed to have the condition. For children, the main concern is that needs to be diagnosed correctly and treated properly because it can look like unipolar depression, ADHD, or conduct disorder. Young children, adolescents and adults each express the condition differently according to child and adolescent disorders expert Demitri Papolos M.D. and the Child and Adolescent Foundation. There is, however, controversy about this last point.[48]

manifests in late life as well. Some individuals with “hyperthymic” temperament (or “hypomanic” personality style) who experience depression in later life appear to have a form of . Much more needs to be elucidated about late-life .

Controversy

A debate rages in the medical community on the prevalence of disorders.[49] Concerns have arisen about the potential for overdiagnosis of BD.[50] One controversy has been the validity of the construct of a mental disorder across different cultural perspectives (Lopez & Guarnaccia 2000, Sher & Trull 1996).[51] Culture-bound syndromes represent recurrent patterns of maladaptive behaviors and/or troubling experiences specifically associated with different cultures or localities (APA, 1994b).[52] It can be difficult to distinguish between age-appropriate restlessness, the fidgeting of children with ADHD, and the purposeful busy activity of mania (Harrington & Myatt, 2003).[53] Further complicating the diagnosis: Abused or traumatized children can seem to have when they are actually reacting to horrors in their lives.[54] Assumptions regarding behavior, particularly in regard to diagnosing , ADHD, and mania in children and adolescents, have raised considerable questions regarding unnecessary treatment. Antipsychotic drugs prescribed for the treatment of BD may increase risk to health including heart problems, diabetes, liver failure, and death.[55] “Consequences of overdiagnosis … include exposure to a greater medication burden (in some cases requiring additional monitoring) as well as lesser likelihood of clinical improvement.”[56] When checking for a misdiagnosis of or confirming a diagnosis of , it is useful to consider what other medical conditions might be possible misdiagnoses or other alternative conditions relevant to diagnosis.[

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June 6, 2008 | Filed Under Mental Disorders 

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