This disorder, earlier known as manic depressive psychosis (MDP), is characterised by recurrent episodes of mania and depression in the same patient at different times.
These episodes can occur in any sequence. The patients with recurrent episodes of mania (unipolar mania) are also classified here as they are rare and often resemble the bipolar patients in their clinical features.
Bipolar disorder is a major public health problem, with estimates of lifetime prevalence in the general population of the United States ranging from 1 to 1.6 percent and from 3 to 1.5 percent worldwide.
There is an increased mortality in patients with mood disorders by almost two times the general population. The most important cause of death is suicide, the life-time risk of which is 10-15 times higher in depression. Patients with depression also have higher mortality rates from cardiovascular diseases and comorbid alcohol and drug use disorders. Patients with depression also exhibit a variety of disturbances in immune function.
Bipolar mood disorder has an earlier age of onset (third decade) than recurrent depressive (unipolar) disorder. Unipolar depression, on the other hand, is common in two age groups: late third decade and fifth to sixth decades.
An average manic episode lasts for 3-4 months while a depressive episode lasts from 4-6 months. Unipolar depression usually lasts longer than bipolar depression. With rapid institution of treatment, the major symptoms of mania are controlled within 2 weeks and of depression within 6-8 weeks.
Some patients with bipolar mood disorder have more than 4 episodes per year; they are known as rapid cyclers. About 70-80% of all rapid cyclers are women. When phases of mania and depression alternate very rapidly, the condition is known as ultra-rapid cycling. Some of the factors associated with rapid cycling include the use of antidepressants (especially tricyclic antidepressants), low thyroxin levels, female gender, bipolar II pattern of illness, and the presence of neurological disease.
Over the years, a vast amount of literature has emerged probing the aetiology of mood disorders. However, the aetiology of mood disorders is not known currently, despite several theories having been propounded.
The life-time risk for the first degree relatives of bipolar mood disorder patients is 25%, and of recurrent depressive disorder patients is 20%. The life-time risk for the children of one parent with bipolar mood disorder is 27% and of both parents with bipolar mood disorder is 74%. The concordance rate in bipolar disorders for monozygotic twins is 65% and for dizygotic twins is 20%; the concordance rate in unipolar depression for monozygotic twins is 46% and for dizygotic twins is 20%.
Therefore, genetic factors are very important in making an individual vulnerable to mood disorders, particularly so in bipolar mood disorders. However, environmental factors are also probably important.
Multiple biochemical pathways likely contribute to bipolar disorder, which is why detecting one particular abnormality is difficult. A number of neurotransmitters have been linked to this disorder, largely based on patients' responses to psychoactive agents as in the following examples. The blood pressure drug reserpine, which depletes catecholamines from nerve terminals, was noted incidentally to cause depression. This led to the catecholamine hypothesis, which holds that an increase in epinephrine and nor epinephrine causes mania and a decrease in epinephrine and nor epinephrine causes depression. Drugs used to treat depression and drugs of abuse (e.g., cocaine) that increase levels of monoamines, including serotonin, nor epinephrine, or dopamine, can all potentially trigger mania, implicating all of these neurotransmitters in its etiology. Other agents that exacerbate mania include L-dopa, which implicates dopamine and serotoninre uptake inhibitors, which in turn implicate serotonin. Evidence is mounting of the contribution of glutamate to both bipolar disorder and major depression. A postmortem study of the frontal lobes of individuals with these disorders revealed that the glutamate levels were increased.
Seven bipolar disorder categories are included in DSMV: bipolar I disorder, bipolar II disorder, cyclothymic disorder, substance/medication induced bipolar and related disorder, bipolar and related disorder due to another medical condition, other specified bipolar and related disorder, and unspecified bipolar and related disorder.
The bipolar I disorder criteria represent the modern understanding ofthe classicmanic depressive disorder oraffective psychosis described in the nineteenth century, differing from that classic description only to the extent that neither psychosis nor the lifetime experience of a major depressive episode is a requirement. However, the vast majority of individuals whose symptoms meet the criteria for a fully syndromal manic episode also experience major depressive episodes during the course of their lives.
Bipolar II disorder, requiring the lifetime experience of at least one episode of major depression and at least one hypomanie episode, is no longer thought to be a "milder" condition than bipolar I disorder, largely because of the amount of time individuals with this condition spend in depression and because the instability of mood experienced by individuals with bipolar II disorder is typically accompanied by serious impairment in work and social functioning.
The diagnosis of cyclothymic disorder is given to adults who experience at least 2 years (for children, a full year) of both hypomanie and depressive periods without ever fulfilling the criteria for an episode of mania, hypomania, or major depression.
Depressive phases are the most prevalent component of bipolar disorders, even with modern treatment. Bipolar depressive morbidity is often misdiagnosed and is limited in response to available treatments. These conditions are especially debilitating and are associated with psychiatric comorbidity, substance abuse, functional disability, and increased mortality owing to early suicide and accidents, and later medical illnesses. There is growing awareness that bipolar depression is one of the greatest challenges in modern psychiatry. It is essential to differentiate various forms of depression, dysthymia, and dysphoric mixed states of bipolar disorders from the clinical features of more common, unipolar major depressive disorders. In bipolar depression, antidepressant responses often are unsatisfactory, and these agents probably are overused. Emerging treatments, including several anticonvulsant and modern antipsychotic drugs, as well as lithium-alone or in selected combinations are partially effective for bipolar depression. Interest in recognizing bipolar depression and seeking more effective, specific, and safer treatments for it are growing.