Suicide risk is high in bipolar II disorder. Approximately one-third of individuals with bi- polar II disorder report a lifetime history of suicide attempt. The prevalence rates of life- time attempted suicide in bipolar II and bipolar I disorder appear to be similar (32.4% and 36.3%, respectively). However, the lethality of attempts, as defined by a lower ratio of at- tempts to completed suicides, may be higher in individuals with bipolar II disorder com- pared with individuals with bipolar I disorder. There may be an association between genetic markers and increased risk for suicidal behavior in individuals with bipolar dis- order, including a 65-fold higher risk of suicide among first-degree relatives of bipolar II probands compared with those with bipolar I disorder.
Functional Consequences of Bipolar II Disorder
Although many individuals with bipolar II disorder return to a fully functional level be- tween mood episodes, at least 15% continue to have some inter-episode dysfunction, and 20% transition directly into another mood episode without inter-episode recovery. Func- tional recovery lags substantially behind recovery from symptoms of bipolar II disorder, especially in regard to occupational recovery, resulting in lower socioeconomic status de- spite equivalent levels of education with the general population. Individuals with bipolar
II disorder perform more poorly than healthy individuals on cognitive tests and, with the exception of memory and semantic ﬂuency, have similar cognitive impairment as do in- dividuals with bipolar I disorder. Cognitive impairments associated with bipolar II disor- der may contribute to vocational difficulties. Prolonged unemployment in individuals with bipolar disorder is associated with more episodes of depression, older age, increased rates of current panic disorder, and lifetime history of alcohol use disorder.
Major depressive disorder. Perhaps the most challenging differential diagnosis to con- sider is major depressive disorder, which may be accompanied by hypomanic or manic symptoms that do not meet full criteria (i.e., either fewer symptoms or a shorter duration than required for a hypomanic episode). This is especially true in evaluating individuals with symptoms of irritability, which may be associated with either major depressive dis- order or bipolar II disorder.
Cyclothymic disorder. In cyclothymic disorder, there are numerous periods of hypo- manic symptoms and numerous periods of depressive symptoms that do not meet symp— tom or duration criteria for a major depressive episode. Bipolar II disorder is distinguished from cyclothymic disorder by the presence of one or more major depressive episodes. If a major depressive episode occurs after the first 2 years of cyclothymic disorder, the addi- tional diagnosis of bipolar II disorder is given.
Schizophrenia spectrum and other related psychotic disorders. Bipolar II disorder must be distinguished from psychotic disorders (e.g., schizoaffective disorder, schizophrenia, and delusional disorder). Schizophrenia, schizoaffective disorder, and delusional disor- der are all characterized by periods of psychotic symptoms that occur in the absence of prominent mood symptoms. Other helpful considerations include the accompanying symptoms, previous course, and family history.
Panic disorder or other anxiety disorders. Anxiety disorders need to be considered in the differential diagnosis and may frequently be present as co-occurring disorders.
Substance use disorders. Substance use disorders are included in the differential diag~ nosis.
Attention-deficit/hyperactivity disorder. Attention-deficit/hyperactivity disorder (ADHD) may be misdiagnosed as bipolar II disorder, especially in adolescents and children. Many symptoms of ADHD, such as rapid speech, racing thoughts, distractibility, and less need for sleep, overlap with the symptoms of hypomania. The double counting of symptoms to- ward both ADHD and bipolar II disorder can be avoided if the clinician clarifies whether the symptoms represent a distinct episode and if the noticeable increase over baseline re- quired for the diagnosis of bipolar II disorder is present.