Genetic Causes of Bipolar Disorder
Researchers have not yet discovered a single cause of bipolar disorder, which is also known as manic depression. They do, however, agree that there are a few potential causes that may occur either separately or together. Genetics is one of them. According to the National Institutes of Health, bipolar disorder can run in families, to a degree. A person with bipolar disorder is four to six times more likely to have a family member with the disease as well. However, the NIH also states that the disorder is not commonly passed down from the parents. Additionally, it is not common for identical twins to share the disorder, even though their genetics are exactly the same. For this reason, most researchers agree that genetics are only one possible cause of bipolar disorder and that they may only lay the foundation for the disease. In other words, someone with a genetic predisposition may develop bipolar disorder if other related causes are also present.
Structural Causes of Bipolar Disorder
The structure and function of the brain may also play a role in determining whether or not a person develops bipolar disorder. According to the Mayo Clinic, the brains of people with bipolar disorder have a significantly different structure than those without the disease. The National Institutes of Health reports this as well, adding that the brains of people with bipolar disorder even differ from those of people with other mental illnesses, with one exception: schizophrenia. These two mental health disorders are actually closely related, and the NIH reports that this is further evidence that brain structure plays a role in the development of bipolar disorder. Differences in neurotransmitters may also play a role in the disorder. Neurotransmitters, such as norepinephrine and serotonin, are the brain's messenger hormones. If their levels are off, or if they are not functioning properly, they can greatly affect how messages are transmitted in the brain--in particular, those related to mood.
Environmental Causes of Bipolar Disorder
Another potential cause of bipolar disorder is the environment. The environment includes such aspects as childhood upbringing, levels of stress and other life events (such as a death in the family or a job loss). The Mayo Clinic reports that environmental factors play "a casual role" in bipolar disorder. In other words, while they may contribute to the development of the disorder, environmental factors are generally not the sole cause. Another environmental factor that is thought to potentially contribute to bipolar disorder is substance abuse. According to the National Institutes of Health, the two are linked; however, the relationship between them is not entirely understood. Substance abuse may trigger a bipolar episode or may begin after the disorder makes its debut. Further research into determining the exact causes of bipolar disorder is in progress.
