Bipolar Disorder

Depressive episodes consist of either depressed mood or anhedonia with five or more of the following concomitant symptoms: (1) significant decrease or increase in sleep, and/or (2) appetite, (3) low energy, (4) psychomotor retardation or agitation, (5) excessive guilt, (6) feelings of worthlessness, (7) poor concentration, (8) difficulty making decisions, and (9) recurrent thoughts of death, suicidal ideation, or a suicide attempt.

Bipolar disorder is divided into two primary types. Bipolar I disorder is diagnosed when a patient experiences a manic episode. Typically, these patients experience both manias and major depressive episodes; however, the presence of a mania alone is sufficient to make the diagnosis. Bipolar II disorder is diagnosed when a patient experiences at least one hypomania and at least one depressive episode. There are related illnesses that fall within the bipolar spectrum but do not meet the criteria for full bipolar disorder. These include patients who experience medication-induced mania or hypomania, as well as cyclothymia.

The epidemiology of bipolar disorder is relatively consistent throughout the world and does not appear to vary significantly between ethnic groups. Population-based studies demonstrated approximately 0.6% prevalence for bipolar disorder type I, 0.4% for bipolar disorder type II, and 1.4% for subthreshold bipolar disorder. There is not a significant gender difference in predilection for this illness. Of interest, the first episode is more likely to be a mania in men and a depressive event in women. The onset of bipolar disorder symptoms generally occurs in adolescence, particularly in the late teens. Onset of bipolar disorder is usually in the early 20s for both men and women.

Bipolar disorder genetics are complex and indicate an overlapping risk with schizophrenia. Twin studies demonstrate that bipolar disorder is strongly heritable. Estimates suggest that up to 80% of risk for bipolar disorder may be inherited. A subunit of L-type calcium channels is among the first genes consistently associated with bipolar disorder.

Functional neuroimaging studies point to significant effects on the anterior limbic network, with particular activation of the amygdala, striatum, and thalamus in bipolar disorder patients when compared with healthy control subjects. However, these studies are limited by small sample size, lack of control for medication, and a mix of mood states at the time patients were scanned. The understanding of bipolar disorder at a cellular and molecular level has advanced from a focus primarily on neurotransmitters, where there are important abnormalities, to an increased focus on signaling pathways and cellular plasticity and resilience.

Lithium preparations were the first effective therapy for bipolar disorder. Several additional classes of medications subsequently demonstrated efficacy. Current pharmacologic preferences include lithium, still considered to be one of the most effective treatments, as well as certain anticonvulsants, that is, valproic acid, lamotrigine, and carbamazepine, and second-generation antipsychotic medications. The treatment of bipolar depression remains a particular challenge, with relatively few medications demonstrating clear efficacy. However, there are some very valuable nonmedication treatment modalities available. Electroconvulsive therapy (ECT) is typically used during severe episodes or when other treatments are not effective. Structured psychosocial interventions, such as cognitive-behavioral therapy, are also useful in illness management.

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