Bipolar disorder Health Article

Definition

Bipolar, or manic-depressive, disorder is a mood disorder that causes radical emotional changes and mood swings, from manic highs to depressive lows. The majority of bipolar individuals experience alternating episodes of mania (an elevated or euphoric mood or irritable state) and depression.

Description

In the United States alone, bipolar disorder afflicts an estimated three million people. According to a report by the National Institutes of Mental Health, the disorder costs over $45 billion annually. The average age of onset of bipolar disorder is from adolescence through the early twenties. However, because of the complexity of the disorder, a correct diagnosiscan be delayed for several years or more.

The Diagnostic and Statistical Manual of Mental Disorders,fourth edition text revised (DSM-IV-TR), the diagnostic standard for mental health professionals in the United States, defines four separate categories of bipolar disorder: bipolar I, bipolar II, cyclothymia, and bipolar not otherwise specified (NOS).

Bipolar I disorder is characterized by manic episodes, the "high" of the manic-depressive cycle. A bipolar patient experiencing mania often has feelings of self-importance, elation, talkativeness, increased sociability, and a desire to embark on goal-oriented activities, coupled with the characteristics of irritability, impatience, impulsiveness, hyperactivity, and a decreased need for sleep. Usually this manic period is followed by a period of depression, although a few bipolar I individuals may not experience a major depressive episode. Mixed states, where both manic or hypomanic symptoms and depressive symptoms occur at the same time, also occur frequently with bipolar I patients (for example, depression with the racing thoughts of mania). Also, dysphoric mania is common (mania characterized by anger and irritability).

Bipolar II disorder is characterized by major depressive episodes alternating with episodes of hypomania, a milder form of mania. Bipolar depression may be difficult to distinguish from unipolar depression (depression without mania, as found in major depressive disorder). Patients with bipolar depression tend to have extremely low energy, retarded mental and physical processes, and more profound fatigue(for example, hypersomnia—a sleep disorder marked by a need for excessive sleep or sleepiness when awake) than people with unipolar depression.

Cyclothymia refers to the cycling of hypomanic episodes with depression that does not reach major depressive proportions. A third of patients with cyclothymia will develop bipolar I or II disorder later in life.

A phenomenon known as rapid cycling occurs in up to 20% of bipolar I and II patients. In rapid cycling, manic and depressive episodes must alternate frequently—at least four times in 12 months—to meet the diagnostic definition. In some cases of "ultra-rapid cycling," the patient may bounce between manic and depressive states several times within a 24-hour period. This condition is very hard to distinguish from mixed states.

Bipolar NOS is a category for bipolar states that do not clearly fit into the bipolar I, II, or cyclothymia diagnoses.

Causes and symptoms

The source of bipolar disorder has not been clearly defined. Because two-thirds of bipolar patients have a family history of emotional disorders, researchers have searched for a genetic link to the disorder. Several studies have uncovered a number of possible genetic connections to the predisposition for bipolar disorder. There is significant evidence that correlates bipolar II with genetic causes. Studies have shown that identical twins have an 80% concordance rate (presence of the same disorder). Additionally, studies have demonstrated that the disorder is transmitted to children by autosomal dominant inheritance. This means that either affected parent (father or mother) has a 50% chance of having a child (regardless if the child is male or female) with the disorder.

Further studies concerning the genetic correlations have revealed specific chromosomes (the structures that contain genes) that contain mutated genes. Susceptible genes are located in specific regions of chromosomes 13, 18, and 21. The building blocks of genes, called nucleotides, are normally arranged in a specific order and quantity. If these nucleotides are repeated, a genetic abnormality usually results. Recent evidence suggests that a special type of nucleotide repeat is observed in persons with bipolar II on chromosome 18. However, the presence of this sequence does not worsen the disorder or change the age of onset. It is currently thought that expression of bipolar II involves multiple mutated genes. Further research is ongoing to discover precise mechanisms and to develop genetic markers (gene tags) that would predict which individuals are at higher risk.

Another possible biological cause for bipolar disorder under investigation is the presence of an excessive calcium buildup in the cells. Also, dopamine and other neurochemical transmitters (the chemicals that transmit messages from nerve cell to nerve cell) appear to be implicated in bipolar disorder and these are under intense investigation.

Over half of patients diagnosed with bipolar disorder have a history of substance abuse. There is a high rate of association between cocaine abuse and bipolar disorder. Some studies have shown up to 30% of abusers meeting the criteria for bipolar disorder. The emotional and physical highs and lows of cocaine use correspond to the manic depression of the bipolar patient, making the disorder difficult to diagnose.

For some bipolar patients, manic and depressive episodes coincide with seasonal changes. Depressive episodes are typical during winter and fall, and manic episodes are more probable in the spring and summer months.

Symptoms of bipolar depressive episodes include low energy levels, feelings of despair, difficulty concentrating, extreme fatigue, and psychomotor retardation (slowed mental and physical capabilities). Manic episodes are characterized by feelings of euphoria, lack of inhibitions, racing thoughts, diminished need for sleep, talkativeness, risk taking, and irritability. In extreme cases, mania can induce hallucinationsand other psychotic symptoms such as grandiose delusions(ideas that the person affected is extremely important or has some unrecognized talent or insight).