Bipolar Disorder: What causes it?

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Author: Mood Disorders Association of BC


Bipolar disorder is a brain disorder that results in extreme changes of mood, energy and effects one’s ability to function. Although research has greatly increased our understanding of why someone might develop bipolar disorder, there is no simple answer as to the precise cause.

Genetic factors

Scientists believe that bipolar disorder is the result of interplay between genetic and environmental factors. Current theories suggest that a person inherits a “vulnerability” to bipolar illness, meaning they are more susceptible 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 play a role in that they can lead to the onset of the illness or “trigger” an episode (a relapse of symptoms) in someone who already has the illness.

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


It is clear that even if a person has a family member with the illness, only a minority will eventually develop bipolar illness. There is another part to this equation – environmental factors. Researchers believe that in some individuals, stressful life events that can trigger the illness. Stressful events are varied and 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 abuse may also play a role

It is important to remember that what is stressful to one person maybe 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.

Biological factors

Researchers have also looked at what might be the activities in the brain that cause these extremes in mood and impaired ability to function.There is evidence to suggest that bipolar disorder is the result of abnormalities in the way some of the nerve cells in our brain communicate among one another. Nerve cells communicate with each other through chemical messengers called neurotransmitters. When there are problems in the functioning of these neurotransmitters, the communication system in the brain can be disrupted.

The cause of bipolar disorder is similar to our understanding of many other chronic illnesses.For example, with heart disease a person 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 known for decades that a link exists between neurotransmitters and mood disorders, as specific medications which alter these transmitters can also relieve mood disorders. In short, researchers are quite certain that the neurotransmitter system is at least part of the cause of bipolar disorder, but further research is still needed to define its exact role.

So the bottom line, according to today’s thinking, is that if you have bipolar disorder, you were likely born with the possibility of developing this disorder, and for many a stressful life event and/or upbringing can trigger the onset or lead to recurring episodes.


About the author

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The Mood Disorders Association of BC is a member of the BC Partners for Mental Health and Addictions 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.