By an underlying problem with specific brain circuits and the balance of brain chemicals called neurotransmitters.
In most people with bipolar disorder, there is no clear cause for the periods (episodes) of extreme happiness and high activity or energy (mania) or depression and low activity or energy (depression). The following may trigger a manic episode: Childbirth. Medicines such as antidepressants or steroids. Bipolar disorder is a condition in which a person has periods of depression and periods of being extremely happy or being cross or irritable. In addition to these mood swings, the person also has extreme changes in activity and energy levels. Experts believe bipolar disorder is partly caused by an underlying problem with specific brain circuits and the balance of brain chemicals called neurotransmitters. Three brain chemicals -- noradrenaline (norepinephrine), serotonin, and dopamine -- are involved in both brain and bodily functions. Doctors don't completely understand the causes of bipolar disorder. But they've gained a greater understanding in recent years of the bipolar spectrum, which includes the elated highs of mania to the lows of major depression, along with various mood states between these two extremes. There may be no single cause of bipolar disorder (aka manic depression). Instead, research indicates the causes of bipolar disorder are probably a combination of biochemical, genetic and environmental factors that may trigger and perpetuate the chemical imbalances in the brain. Researchers have discovered that some people with bipolar disorder have: 1  biochemical imbalances of hormones and certain neurotransmitters in the brain; especially dopamine, serotonin, norepinephrine, and acetylcholine. 2  1. 3  an over-secretion of cortisol, a stress hormone. And while the causes of bipolar disorder are still unknown, there are a number of factors that are believed to play a role, including genetics, brain chemicals, environmental factors and sometimes medical illnesses. Read about: 1  Genetics. 2  Brain chemicals. 3  Environmental. 4  Medical illness. 5  Pregnancy.  Causes of bipolar disorder. The exact cause of bipolar disorder is unknown. Experts believe there are a number of factors that work together to make a person more likely to develop the condition. These are thought to be a complex mix of physical, environmental and social factors. If there is an imbalance in the levels of one or more neurotransmitters, a person may develop some symptoms of bipolar disorder. For example, there is evidence episodes of mania may occur when levels of noradrenaline are too high, and episodes of depression may be the result of noradrenaline levels becoming too low. Causes. The exact cause of bipolar disorder is unknown, but several factors may be involved, such as: 1  Biological differences. 2  People with bipolar disorder appear to have physical changes in their brains. 3  The significance of these changes is still uncertain but may eventually help pinpoint causes. 4  Neurotransmitters. The exact cause of bipolar disorder is unknown, but several factors may be involved, such as: 1  Biological differences. 2  Neurotransmitters. 3  Inherited traits. 4  Symptoms. 5  Risk factors.
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001924/ http://www.webmd.com/bipolar-disorder/guide/bipolar-disorder-causes http://www.healthyplace.com/bipolar-disorder/bipolar-information/causes-of-bipolar-disorder-what-causes-bipolar-disorder/ http://www.blackdoginstitute.org.au/public/bipolardisorder/causes.cfm http://www.nhs.uk/Conditions/Bipolar-disorder/Pages/Causes.aspx http://www.mayoclinic.org/diseases-conditions/bipolar-disorder/basics/causes/CON-20027544
the cause of bipolar disorder