Heritability:

Bipolar disorder appears to run in families, that is, a vulnerability for bipolar disorder may be inherited. 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. The rate of prevalence of bipolar disorder is roughly equal (around 3%) in men and women.

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.

Recent genetic research:

Bipolar disorder is considered to be primarily a genetically caused disorder. 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. Relatives of persons with Bipolar Disorder also have an increased incidence of having unipolar depression.

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.

Medical imaging:

Researchers are using advanced medical imaging techniques to examine brain function and structure in people with bipolar disorder. 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.

Personality types:

An evolving literature exists concerning the nature of personality and temperament in Bipolar Disorder patients, compared to Major Depressive Disorder (unipolar) patients and normals. 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.

Research into new treatments:

In late 2003, researchers at McLean Hospital in Belmont, Massachusetts have 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 polyunsaturated 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 20 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.