Nature vs. Nurture: The Causes of Bipolar Disorder

What causes bipolar disorder? Scientists aren’t actually sure, but are taking into consideration several risk factors, such as genes, brain structure, and environmental causes.

Genes

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Credit to flickr.com user CIFOR. Used with permission under a Creative Commons license.

Genetic studies of twins have shown promising results with regards to bipolar disorder. According to a a study by Berit Kerner, “The heritability of bipolar disorder based on concordance rates for bipolar disorder in twin studies has been estimated to be between 60% and 80%.” However, if one identical twin develops Bipolar I, the rate of the other twin developing it is roughly 40%, compared to fraternal twins at 5%. Parents have a 10 to 15% chance to pass bipolar disorder to their children if one parent has the disorder, compared to 30 to 40% if both do. This means genetics play a crucial role in the transmission of bipolar disorder.

Brain Structure

Recent evidence suggests that the structure of the brain may contribute to people developing bipolar disorder. MRI studies have found the over-activation of the amygdala, which processes memory, helps decision-making, and controls emotional reactions. People who are manic showed decreased activity in the interior frontal cortex, which assists problem solving, memory, language, judgment, and impulse control. Certain psychiatric medications work on neurotransmitters, suggesting that these messenger chemicals play a significant role in the function of bipolar disorder, but no one knows how exactly they’re responsible.

Environmental Factors

Stress is a significant predictor of bipolar disorder in people who are susceptible to the disease. Life events such as childbirth, trauma, job loss, or grief over a death in the family may trigger a mood episode. My mania and subsequent psychosis was set off by the birth of my first child, Nolan, but my second child’s birth did not trigger anything. However, substance abuse, hormonal issues, and altered health habits can also spark the illness.

Many factors set in motion the development of bipolar disorder. With more research, scientists will discover the roots of the disease, and possibly be able to prevent it in the future.

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About Cassandra Stout

Freelance writer Cassandra Stout blogs at The Bipolar Parent, a comprehensive resource for parents with mental illnesses. She is currently working on Committed, her forthcoming memoir detailing her time spent in a mental hospital while separated from her husband and newborn. Cassandra holds degrees from the University of Arizona in Creative Writing and Journalism, and is a member of the Pacific Northwest Writers Association. She balances her literary work with raising her children, feeding her cat, and managing her bipolar disorder.
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7 Responses to Nature vs. Nurture: The Causes of Bipolar Disorder

  1. dyane says:

    I love the title of this post, Cass! I didn’t know so many of these facts, so it’s really interesting to take it all in. From time to time I read announcements about astronomical amounts of money donated to bipolar disorder research. I hope that some significant advances are made in our lifetime! (Not to mention a cure….)

    • Thank you, Dyane! I appreciate your taking the time to read and comment! And yes, I would love to see a cure in our lifetime. No amount of research is enough until a cure is found.

  2. super informative…great post…!! learn something new every day…

  3. Good information. I grew up with a wonderfully, eccentric bipolar father, so I know it’s in my genes for sure!

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