with other related mood disorders (e.g., major depressive disorder, dysthymia). However, the Fifth Edition (DSM-5)4 placed bipolar disorder in a new category—“Bipolar and Related Disorders.” Bipolar disorder involves experiencing two divergent emotional states: mania and depression, from which the disorder got its former name of manic-depressive illness. During manic episodes, people feel excited, self-confident, energetic, and euphoric, and often have a decreased need for sleep. During depressive episodes, they feel sad, despondent, and listless. However, bipolar disorder is more complicated than a simple division between mania and depression. Many people with bipolar disorder go through periods when their mood is balanced, or euthymic (i.e., not euphoric, manic, or depressed), even without medication. Some people experience a “mixed state” that combines the features of mania and depression at the same time. Mania does not always involve feeling good, however. Some people feel irritable instead, especially when substance use is involved. Also, manic episodes can vary in severity. DSM-5 divides manic episodes into two types: ● Mania—Lasting at least a week and causing significant impairment in social and occupational functioning or requiring hospitalization ● Hypomania—Lasting at least 4 days, often with less severity (i.e., the change may be noticeable but may not impair functioning) Some people with bipolar disorder experience psychotic features, such as delusions and hallucinations. 2 ADVISORY Behavioral Health Is Essential To Health • Prevention Works • Treatment Is Effective • People Recover Estimates of the lifetime prevalence of bipolar disorder in the United States range from 1 percent13 to almost 4 percent.14* *The disparity between these estimates may be the result of algorithmic or other methodological Estimates for 12-month prevalence range from less than 1 percent4,13 to 2.6 percent.15 An analysis by Kessler, Petukhova, Sampson, Zaslavsky, and Wittchen16 estimated the projected lifetime risk of developing bipolar disorder (in the United States) to be 4.1 percent. One study found that individuals with bipolar disorder reported a significantly greater incidence of childhood trauma (such as sexual abuse or physical neglect) and internalized shame compared with a control group without bipolar disorder.17 Another study found a history of childhood trauma in approximately 50 percent of individuals with bipolar disorder, and multiple forms of abuse were present in approximately 33 percent of individuals with bipolar disorder.18 Other studies have also found an association between childhood trauma and a more complex or severe course of bipolar disorder.18,19 The types of bipolar disorder DSM-5 organizes bipolar disorder into several different diagnostic categories based, in large part, on the frequency and severity of the manic and depressive episodes. To be diagnosed with bipolar I disorder, an individual must have had at least one episode of mania. People with bipolar I disorder experience depression, but having a major depressive episode is not necessary for the diagnosis.4 The diagnostic criteria for bipolar II disorder include having at least one episode of hypomania that lasts at least 4 days and a major depressive episode that lasts at least 2 weeks. Between 5 and 15 percent of people with bipolar II disorder eventually have a manic episode that reclassifies their condition as bipolar I disorder.4 Bipolar II disorder is sometimes misunderstood as being less severe than bipolar I disorder. It is not. Like bipolar I, bipolar II is a chronic illness, and the depressive phases of bipolar II can be severe and disabling.4,20,21 Significant numbers of individuals have bipolar symptoms at subthreshold or subsyndromal levels (i.e., below levels required for a diagnosis of bipolar I or II).22,23 Some researchers have suggested that subthreshold bipolar symptom presentations be included in a broader category called bipolar spectrum disorders,22 which could also include other types of bipolar disorders identified in DSM-5, such as cyclothymic disorder and substance/medicationinduced bipolar and related disorder. The core patterns of bipolar disorder are illustrated in Exhibit 1. Challenges of Diagnosing Bipolar Disorder Some research suggests that bipolar disorder is underdiagnosed. One reason for underdiagnosis may be that people with bipolar disorder tend to seek treatment during a depressive phase, when manic or hypomanic episodes (or subthreshold symptoms) may not be readily remembered or may remain undetected by a clinician.24,25 If providers do not elicit information from depressed patients about past episodes of mania and hypomania, these patients may be diagnosed with unipolar depression instead of bipolar disorder. However, there is also evidence that bipolar disorder is overdiagnosed. A study of psychiatric outpatients found that less than half of those diagnosed with bipolar disorder actually had the disorder when researchers assessed them using the Structured Clinical Interview for DSM-IV.26 Other mental disorders can also be mistakenly diagnosed as bipolar disorder because of symptoms that overlap. For example, one study found that 40 percent of people with borderline personality disorder had been misdiagnosed as having bipolar disorder.27 Bipolar