Cause of Bipolar Disorder


While bipolar disorder is better understood now than it ever has been before, we still do not have a complete understanding of what causes the disorder. As with many mental illnesses, most experts believe that bipolar disorder develops as a result of a combination of genetic, neurochemical, and environmental factors.


Many studies have clearly shown that bipolar disorder has a hereditary component. At least one study has found that half of bipolar individuals have a family member with a mood disorder of some type, and studies have consistently shown that people with a bipolar relative are at an increased risk of developing the disorder themselves. Studies on identical twins, who are share the same genes, have found that when one identical twin has bipolar disorder, the other has a 40-70% chance of also developing the disorder over their lifetime--significantly greater than non-identical siblings.


Many hypotheses on the cause of bipolar disorder focus on neurotransmitters, the brain’s chemical messengers. Three neurotransmitters--norepinephrine, serotonin, and dopamine--have been linked to mood disorders like depression and bipolar disorder. Most of the drugs commonly used to treat mood and psychiatric disorders affect the levels and balance of these neurotransmitters in the brain. Scientists still do not know the precise role these chemicals play in mood disorders like bipolar, including whether they are the root cause or a byproduct of some other brain problem, but they know they are involved in some way and that targeting them can be an effective treatment.

The Environment

While the cause of bipolar disorder is thought to be largely biological, it is also clear that environmental factors can play a role. Stressful life events can trigger an episode in someone with bipolar or with a genetic predisposition for developing the disorder, although the illness tends to progress on its own once triggered. Substance abuse can also play a role in the presentation of the disorder, although it is not considered a cause.

In summary, bipolar disorder is a complex illness that appears to be the result of several factors. One of the best explanations we have at the moment is that bipolar disorder is typically caused by life stressors interacting with an inherited or biological vulnerability to the disorder.

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