Bipolar disorder is a mental health condition that causes extreme shifts in mood, energy, and behavior. This disorder most often appears in late adolescence or early adulthood, although symptoms can begin at any time of life.
People with bipolar disorder experience both dramatic "highs," called manic episodes, and "lows," called depressive episodes. These episodes can last from hours to weeks, and many people have no symptoms between episodes. Manic episodes are characterized by increased energy and activity, irritability, restlessness, an inability to sleep, and reckless behavior. Depressive episodes are marked by low energy and activity, a feeling of hopelessness, and an inability to perform everyday tasks. People with bipolar disorder often have repeated thoughts of death and suicide, and they have a much greater risk of dying by suicide than the general population.
Manic and depressive episodes can include psychotic symptoms, such as false perceptions (hallucinations) or strongly held false beliefs (delusions). Mixed episodes, which have features of manic and depressive episodes at the same time, also occur in some affected individuals.
Bipolar disorder often occurs with other mental health conditions, including anxiety disorders (such as panic attacks), behavioral disorders (such as attention-deficit/hyperactivity disorder), and substance abuse.
Bipolar disorder is a common form of mental illness. At some point during their lifetime, 2.4 percent of people worldwide and 4.4 percent of people in the United States are diagnosed with this condition.
Very little is known for certain about the genetics of bipolar disorder. Studies suggest that variations in many genes, each with a small effect, may combine to increase the risk of developing the condition. However, most of these genetic variations have been identified in single studies, and subsequent research has not verified them. It is unclear what contribution each of these changes makes to disease risk. Some of the genetic changes associated with bipolar disorder have also been found in people with other common mental health disorders, such as schizophrenia. Understanding the genetics of bipolar disorder and other forms of mental illness is an active area of research.
Studies suggest that nongenetic (environmental) factors also contribute to a person's risk of developing bipolar disorder. Stressful events in a person's life, such as a death in the family, can trigger disease symptoms. Substance abuse and traumatic head injuries have also been associated with bipolar disorder. It seems likely that environmental conditions interact with genetic factors to determine the overall risk of developing this disease.
The inheritance pattern of bipolar disorder is unclear. Overall, the risk of developing this condition is greater for first-degree relatives of affected individuals (such as siblings or children) as compared to the general public. For unknown reasons, the risk of inheriting the disorder appears to be higher in some families than in others. However, most people who have a close relative with bipolar disorder will not develop the condition themselves.
Many individuals with bipolar disorder have relatives with other mood, anxiety, and psychotic disorders (such as depression or schizophrenia). These disorders may run in families in part because they share some genetic risk factors with bipolar disorder. However, these conditions are relatively common in the general population, and so it would not be surprising to see more than one case in a family just by chance.