Bipolar disorder appears to run in families. The rate of suicide is higher in people who have bipolar disorder than in the general population. In fact, people with bipolar disorder are about twice as likely to commit suicide as those suffering from major depression (12% to 6%).
The rate of prevalence of bipolar disorder is roughly equal in men and women. Lifetime risk of bipolar I disorder is often quoted as around 1%, but when bipolar II is included the true rate may be around 4%.
More than two-thirds of people with bipolar disorder have at least one close relative with the disorder or with unipolar major depression, indicating that the disease has a heritable component. Studies seeking to identify the genetic basis of bipolar disorder indicate that susceptibility stems from multiple genes. Scientists are continuing their search for these genes using advanced genetic analytic methods and large samples of families affected by the illness. The researchers are hopeful that identification of susceptibility genes for bipolar disorder, and the brain proteins they code for, will make it possible to develop better treatments and preventive interventions targeted at the underlying illness process.
Bipolar disorder is considered to be a result of complex interactions between genes and environment. The monozygotic concordance rate for the disorder is 70%. This means that if a person has the disorder, an identical twin has a 70% likelihood of having the disorder as well. Dizygotic twins have a 23% concordance rate. Children of a bipolar parent have a 50% chance of developing schizophrenia, schizoaffective or bipolar disorder. First degree relatives are seven times more likely to develop the condition than the general population.
In 2003, a group of American and Canadian researchers published a paper that used gene linkage techniques to identify a mutation in the GRK3 gene as a possible cause of up to 10% of cases of bipolar disorder. This gene is associated with a kinase enzyme called G protein receptor kinase 3, which appears to be involved in dopamine metabolism, and may provide a possible target for new drugs for bipolar disorder.
Researchers are using advanced brain imaging techniques to examine brain function and structure in people with bipolar disorder, particularly using the functional MRI. An important area of imaging research focuses on identifying and characterizing networks of interconnected nerve cells in the brain, interactions among which form the basis for normal and abnormal behaviors. Researchers hypothesize that abnormalities in the structure and/or function of certain brain circuits could underlie bipolar and other mood disorders. Better understanding of the neural circuits involved in regulating mood states may influence the development of new and better treatments, and may ultimately aid in diagnosis.
An evolving literature exists concerning the nature of personality and temperament in bipolar disorder patients, compared to major depressive disorder (unipolar) patients and non-sufferers. Such differences may be diagnostically relevant. Using MBTI continuum scores, bipolar patients were significantly more extroverted, intuitive and perceiving, and less introverted, sensing, and judging than were unipolar patients. This suggests that there might be a correlation between the Jungian extraverted intuiting process and bipolar disorder.
In late 2003, researchers at McLean Hospital found tentative evidence of improvements in mood during EP-MRSI imaging, and attempts are being made to develop this into a form which can be evaluated as a possible treatment.
It has been hypothesized that bipolar disorder may be the result of poor membrane conduction in the brain and that one possible cause may be a deficiency in omega-3 fatty acids. Following an encouraging small-scale study conducted by Andrew Stoll at Harvard University's McLean Hospital, the Stanley Foundation is sponsoring research regarding the beneficial claims, and several large scale trials of treatment using omega-3 fatty acids are under way.
NIMH has initiated a large-scale study at twenty sites across the U.S. to determine the most effective treatment strategies for people with bipolar disorder. This study, the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD), will follow patients and document their treatment outcome for 5 to 8 years. For more information, visit the Clinical Trials page of the NIMH Web site.
In 2005 two double blind placebo controlled studies were underway at Harvard University and University of Calgary to determine if the trends noted in several open label trials using a mineral, vitamin and amino acid supplement called E.M. Power would continue to demonstrate effectiveness. In preliminary studies, as many as 70% of patients taking the supplements were free of symptoms after slowly having withdrawn from psychotropic medications.
For immediate management of mania, left coloric vestibular stimulation has proven effective in dramatically and rapidly stopping mania for up to 24 hours. Currently there are only case reports, and there has been no organized research on use of the procedure for acute mania.
Another avenue for treatment that has, at times been curative for resolving manic psychosis is by treating an underlying infections such as Lyme disease. Results in these cases suggest that the term bipolar disorder may not accurately represent the actual biological disorders which meet the DSM-IV requirement for a bipolar disorder. For an unknown number of patients, the problem may be a kind of immune mediated disorder provoked by Lyme disease (Toxoplasmosis, Bornea virus), or any or a number of other chronic infections, including something as common as the flu.
Many famous people are believed to have been affected by bipolar disorder, based on evidence in their own writings and contemporaneous accounts by those who knew them. Bipolar disorder is found in disproportionate numbers in people with creative talent such as artists, musicians, authors, poets, and scientists, and it has been speculated that the mechanisms which cause the disorder may be related to those responsible for creativity in these persons. (Many of the historical creative talents commonly cited as bipolar were "diagnosed" retrospectively after their deaths and thus the diagnoses are unverifiable; however, in cases diagnosed in recent decades there does seem to be at least some correlation between bipolar disorder and creativity.) The possible explanation for this is that hypomanic phases of the illness allow for heightened concentration on activities and the manic phases allow for around-the-clock work with minimal need for sleep.