Bipolar disorder is a mood disorder in which individuals experience mania and extremely high euphoric mood, which may alternate with bouts of depression. The definitive cause of the disorder is unknown; however, risk factors include inherited genes, differences in brain development and environmental stressors. According to the National Institute of Mental Health, the prevalence of bipolar disorder in individuals ages 18 and older is 2.6 percent.
Genes
One possible cause of bipolar disorder is family inheritability. As reported by the National Institute for Mental Health, persons who have a close relative with bipolar disorder are up to six times more likely to have the disorder themselves. Not all persons with a family history, however, develop the disorder. Identical twin studies have shown that one twin may have the disorder while the other, who has identical genes, does not develop it, according to the National Institute of Mental Health. This suggests that other risk factors are at play.
Brain Functioning
Brain imaging has shown that the brains of individuals with bipolar disorder function differently than individuals without. According to the National Institute of Mental Health, imaging has shown that bipolar brains function in a way that makes the individual likely to have difficulty controlling their mood. MayoClinic.com also reports that disproportion of neurotransmitters as well as physical differences in the brain may contribute to symptoms of bipolar disorder. Robert Weis, author of "Introduction to Child and Adolescent Psychology," also indicates that smaller brain structures, including the limbic system responsible for processing emotion, are seen in persons with bipolar disorder and contribute to their symptoms.
Other Risks
Other events and risks can place an individual at greater risk for developing bipolar disorder. These may include significant stress, a history of abuse and a traumatic event such as death. Additionally, hormone imbalances in the body may impact the onset or exacerbation of bipolar symptoms.
References
- National Institute of Mental Health: What are the risk factors for bipolar disorder?
- MayoClinic.com: Bipolar Disorder Causes
- "Introduction to Abnormal Child and Adolescent Psychology"; Robert Weis; 2008
- National Institute of Mental Health: The Numbers Count: Mental Disorders in America
