Bipolar Disorder Defined
Bipolar disorder is a mental illness that affects both the brain's function and a person's behavior. Also called manic depression, bipolar disorder is characterized by fluctuations between two extreme mood states: mania, the high, and depression, the low. While there is no certain cause of bipolar disorder, experts at research institutes, such as the Mayo Clinic, believe it is caused by a combination of factors. These include genetics, the environment, especially stress factors, and changes in the brain. These brain changes may be chemical, structural or both.
Chemical Brain Changes
Different chemicals in the brain cause different reactions. These chemicals, called neurotransmitters, affect how brain cells fire as well as how nerves send information to the brain. They also affect how the brain responds to this information. There are hundreds of types of neurotransmitters. Some of these chemicals, such as serotonin and norepinephrine, are associated with different moods. PsychCentral reports that these chemicals may be out of balance in people who are predisposed to certain psychiatric disorders, including bipolar disorder. This imbalance may exist before an episode of bipolar disorder is triggered, or it may be caused by the episode itself.
Structural Brain Changes
In people with psychiatric disorders, such as bipolar disorder, the brain itself may be different. Both the Mayo Clinic and the National Institute of Mental Health have reported differences between the brains of people with bipolar disorder and those of healthy individuals. MRI studies on brain development have shown similarities between structural changes in the brain and emotional disorders. These include not only bipolar disorder, but also schizophrenia and multidimensional impairment. These changes are thought to begin during childhood. While they may not directly cause bipolar disorder, they may predispose a person to developing it if other risk factors are present.
Other Brain Changes
Additional imaging studies have shown that bipolar disorder not only causes changes in the brain during attacks of mania and depression, but that over time it may lead to structural changes in the brain. The American Journal of Psychiatry published a study that showed differences in brain function during both the manic and depressive phases of bipolar disorder. During the manic phase, overall brain metabolism was unusually high. During the depression phase, on the other hand, mainly the frontal cortex was affected. Another study in Biological Psychiatry reported that over a period of time, people already diagnosed with bipolar disorder experienced changes in certain brain structures. However, it is not entirely known how much of these changes are specific to bipolar disorder alone. Both of these areas are undergoing further research.
