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Bipolar Disorder: What causes bipolar disorder?


Author: Mood Disorders Association of BC


Bipolar disorder is a brain disorder that results in extreme changes of mood, energy and ability to function. Although research has improved our understanding of why someone might develop bipolar disorder, the exact cause is still not known.

Scientists believe that bipolar disorder is the result of a complicated relationship between genetic and environmental factors. Research suggests that a person is born with a "vulnerability" to bipolar illness, which means that they are more prone to developing the disorder. However, this is not the only factor in determining whether a person will become ill. Environmental factors such as stressful life events also appear to play a role in that they can lead to the onset of the illness or "trigger" a relapse of symptoms.

Family, twin and adoption studies show that bipolar disorder can run in families although not everyone with a family history will develop this disorder. People who have first-degree relatives (parents, children, siblings) with a mood disorder are more likely to have a mood disorder. For example, a person with one parent who has bipolar has a 15 to 30% risk for developing the disorder.

Even if a person has a family member with the illness, only a minority will eventually develop bipolar illness. There are also environmental factors to be considered. Researchers believe that in some individuals, stressful life events can trigger the illness. Stressful events might include grief over a death in the family, trauma, loss of a job, the birth of a child or moving into a new home. Alcohol or drug use may also be a factor.


The way that we understand bipolar disorder and its causes is similar to the way that we understand many other chronic illnesses. For example, people with heart disease may inherit the risk or predisposition to develop high blood pressure or heart disease. When this is combined with environmental factors (e.g. obesity, cigarette smoking, high stress, etc.), there is an increased risk of having a heart attack. However, with proper treatment and some lifestyle changes, many illnesses including bipolar disorder can be effectively managed.


Researchers have also studied how the brain works when extremes in mood and impaired ability to function occur. There is evidence to suggest that bipolar disorder is the result of abnormalities in the way the brain functions. Nerve cells communicate with each other through chemical messengers called neurotransmitters. When there are problems in the functioning of these neurotransmitters, communication in the brain can be impacted.

Researchers have known for decades that a link exists between neurotransmitters and mood disorders because specific medications which change these transmitters can also change mood. So, the bottom line, is that if you have bipolar disorder, you were likely born with the predisposition for this disorder, and for many a stressful life event and/or upbringing can trigger the onset of the illness.

It is important to remember that what is stressful to one person may not be stressful to another.

A person's coping skills or their "resiliency" will also impact on how stressful the event is to that person.


About the author

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The Mood Disorders Association of BC is a member of the BC Partners for Mental Health and Substance Use Information. The organization is dedicated to providing support, education, and hope for recovery for those living with a mood disorder or other mental illness. For more, visit or call 1-604-873-0103.


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