The cause of bipolar disorder is not entirely known. Genetic, neuro-chemical and environmental factors probably interact at many levels to play a role in the onset and progression of bipolar disorder. The current thinking is that this is a predominantly biological disorder that occurs in a specific part of the brain and is due to a malfunction of the neurotransmitters (chemical messengers in the brain). As a biological disorder, it may lie dormant and be activated spontaneously or it may be triggered by stressors in life.
Although, no one is quite sure about the exact causes of bipolar disorder, researchers have found some important clues. Bipolar disorder tends to be in the genes, meaning that it runs in families. About half the people with bipolar disorder have a family member with a mood disorder, such as depression.
A person who has one parent with bipolar disorder has a 15 to 25 percent chance of having the condition. A person who has a non-identical twin with the illness has a 25 percent chance of illness, the same risk as if both parents have bipolar disorder.
A person who has an identical twin (having exactly the same genetic material) with bipolar disorder has an even greater risk of developing the illness about an eightfold greater risk than a non-identical twin.
A study of adopted twins (where a child whose biological parent had the illness is raised in an adoptive family untouched by the illness) has helped researchers learn more about the genetic causes vs. environmental and life events causes. Bipolar disorder is primarily a biological disorder that occurs in a specific area of the brain and is due to the dysfunction of certain neurotransmitters, or chemical messengers, in the brain. These chemicals may involve neurotransmitters like norepinephrine, serotonin and probably many others. As a biological disorder, it may lie dormant and be activated on its own or it may be triggered by external factors such as psychological stress and social circumstances.
Environmental factors in bipolar disorder may be a life event which may trigger a mood episode in a person with a genetic disposition for bipolar disorder. Even without clear genetic factors, altered health habits, alcohol or drug abuse or hormonal problems can trigger an episode. Among those at risk for the illness, bipolar disorder is appearing at increasingly early ages. This apparent increase in earlier occurrences may be due to under diagnosis of the disorder in the past. This change in the age of onset may be a result of social and environmental factors that are not yet understood.
Although substance abuse is not considered a cause of bipolar disorder, it can worsen the illness by interfering with recovery. Use of alcohol or tranquilizers may induce a more severe depressive phase.
Yet another cause of bipolar depression is that caused by medications. Medications such as antidepressants can trigger a manic episode in people who are susceptible to bipolar disorder. Therefore, a depressive episode must be treated carefully in those people who have had manic episodes. Because a depressive episode can turn into a manic episode when an antidepressant medication is taken, an anti-manic drug is also recommended to prevent a manic episode. The anti-manic drug creates a ceiling, partially protecting the person from antidepressant-induced mania.
Certain other medications can produce a high that resembles mania. Appetite suppressants, for example, may trigger increased energy, decreased need for sleep and increased talkativeness. After stopping the medication, however, the person returns to his normal mood.