Bipolar disorder--formerly called manic-depressive disorder--is a mood disorder that can cause extreme and uncontrolled swings from dangerous euphoria to incapacitating depression. Although the causes of bipolar disorder are not clear, emotional, structural and chemical changes in the brain hint at underlying brain areas and mechanisms that contribute to the disorder.
Emotional
Emotions reflect our experience of alterations in the brain’s structure and function. Bipolar disorder causes swings in mood from states of mania to states of depression, resulting in a range of emotional changes. According to the National Institute of Mental Health, during manic phases, people can feel full of energy and outgoing, or they can feel jumpy and irritable. On the other extreme, during a depressive phase, people experience feelings of emptiness and hopelessness. In the grip of an extreme episode of mania or depression, patients might experience delusions or hallucinations.
Structural
Bipolar disorder might cause or result from changes in the physical structure of the brain. A study in the February 2004 issue of Bipolar Disorders, research using MRIs of the brains of teen-agers with bipolar disorder found that overall smaller volume of the cerebrum, the brain area responsible for processing sensory information, language and learning and memory among other functions. In addition, the study found that bipolar brains had smaller amygdalas and larger putamens compared to brains of healthy people. In the December 2009 issue of Bipolar Disorder, researchers reported that their review of the literature showed that the structural changes in the brain were present during the first episode of bipolar disorder, suggesting that they cause the disorder rather than result from it.
Chemical
When compared to healthy people, patients with bipolar disorder have different levels of chemical signals called neurotransmitters that allow nerves to communicate with each other. Some levels of hormones, chemical messages made in one tissue that act on another, also change in people with bipolar disorder. Brain levels of opioids as well as neurotransmitters serotonin and dopamine and the stress hormone cortisol have all been implicated in mood disorders, including bipolar disorder, according to a May 2008 Science Update by the National Institute of Mental Health. The medications for bipolar disorder such as anti-depressants, anti-convulsants, lithium, benzodiazepams and anti-psychotics attempt to correct the imbalances in neurotransmitters and hormones and smooth out mood. The same principle holds for the use of electroconvulsive therapy for bipolar disorder. The passage of an electric current through the brain is thought to reset brain chemistry to a more healthy state.
References
- National Institute of Mental Health: What are the Symptoms of Bipolar Disorder?
- “Bipolar Disorder”; Magnetic Resonance Imaging Analysis of Amygdala and Other Subcortical Brain Regions in Adolescents with Bipolar Disorder; M. DelBello et al.; Feb. 2004
- “Bipolar Disorder”; Gray Matter, White Matter, Brain, and Intracranial Volumes in First-episode Bipolar Disorder: A Meta-analysis of Magnetic Resonance Imaging Studies; A. Vita, L. De Peri and E. Sacchetti; Dec. 2009
- National Institute of Mental Health: Science Update
- Mayo Clinic: Bipolar Disorder
