Bipolar Disorder Health Article

Definition

Bipolar disorder is characterized by severe and unusual changes in energy level, mood, and interactions with others. The mood swings associated with bipolar disorder are unpredictable, and range from mania (elevated or irritable mood) to depression (a mood characterized by loss of interest and sadness). Bipolar disorder causes significant impairment in social, occupational, and general functioning.

Description

Bipolar disorder is a manic-depressive psychiatric disorder that causes extreme fluctuations in mood and energy levels, which alternate over long time periods. These episodes are referred to as mania and depression, and appear in cycles throughout life. Between episodes, approximately two-thirds of bipolar patients are free of symptoms, with the remainder experiencing residual symptoms. A small percentage of patients experience chronic incessant symptoms despite treatment.

Bipolar disorder type I is the classic form of the illness, involving recurrent cycles of extreme manic and depressive episodes. Type II bipolar disorder patients never develop severe mania. Type II bipolar patients experience milder episodes called hypomania that alternate with depression. A third type, rapid-cycling bipolar disorder, involves four or more episodes of illness occur within a 12-month period. Multiple episodes may occur within one week or day. Rapid cycling tends to occur later in the course of illness and is most common in women.

Manic episodes are commonly associated with irritability, decreased need for sleep, euphoria (an exaggerated perception of feeling good), social extroversion (excessive friendliness), and feeling more important than one truly is (grandiosity). Depressive episodes are commonly associated with fatigue, impaired concentration and judgment, and altered sleep and appetite patterns. The depressive cycle can further progress to feelings of excessive shame and guilt, and lead to suicidal thoughts. Bipolar disorder is also called manic-depressive psychosis, and is a major affective disorder.

Genetic profile

There is no single gene or environmental factor that causes bipolar disorder. Like other mental illnesses, multiple factors together may contribute to the illness. Bipolar disorder has a strong genetic component. According to the Mayo Clinic, 60% of bipolar cases have a family history of the disease. The Child and Adolescent Bipolar Foundation (CABF) reports that the risk for a child of one bipolar parent to develop the disorder is l5–30%. If both parents have bipolar disorder, the risk for each child increases to 50–75%. The risk in siblings and fraternal twins is 15–25%. The risk in identical twins, who share the same genes, is approximately 70%. Research in identical twins indicates that both genes and other factors play a role in developing bipolar disorder.

No specific gene mutations have been identified that consistently show up in bipolar patients. However, there appears to be a potential genetic correlation between bipolar disorder and mutations 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 in a redundant fashion, a genetic abnormality often results. Some evidence exists for a special type of nucleotide sequence (CAG/CTG repeats) in patients with type II bipolar disorder on chromosome 18. However, not all bipolar patients have this mutation and the presence of this sequence does not worsen the disorder or change the age of onset. Further research is needed to determine which genes are involved in bipolar disorder. The specific genetic defect for bipolar disorder has not yet been identified, and it is likely that both genetic and environmental factors contribute to the disease.

Demographics

According to the National Institutes of Mental Health (NIMH), approximately 1–1.3% of the United States adult population has bipolar disorder. It is estimated that approximately 2.3 million adult Americans are affected. Approximately 0.8% of the population has bipolar disorder type I, and 0.5% of the population has bipolar disorder type II. Approximately 25–50% of individuals with manic-depressive disorders attempt suicide, with 11% actually committing suicide. No racial predilection exists. While bipolar type I occurs equally in both sexes, type II and rapid-cycling bipolar disorder is more common in females than in males. Women may also be at increased risk of developing subsequent episodes in the immediate time period after giving birth. Bipolar disorder runs in families, with the rate disease in identical twins being higher than that in fraternal twins. The age of onset varies greatly. The age range of onset may be in early childhood or up to 50 years of age, with a mean of 21 years. The most frequent age of onset lies between 15 and 19 years of age. The second most frequent age of onset is between 20 and 24 years of age. Some patients previously diagnosed with recurrent major depression may have bipolar disorder and not develop a manic episode until 50 years of age. However, for most patients, mania onset after 50 years of age is due to other medical disorders such as cerebrovascular disease.