What part of the brain does bipolar II disorder affect?

Updated April 17, 2017

The brain plays an important role in controlling emotions, thoughts, and other important functions. Therefore, having a brain disorder like bipolar I can affect these functions. But bipolar disorder doesn't affect the entire brain; only parts of it.

Bipolar disorder

The brain disorder known as bipolar disorder manic-depressive illness can cause changes to a person's mood, their energy and activity levels, as well as their ability to perform daily functions at home, work and school. The symptoms of the disorder are usually first noticed during youth or as a young adult.


Bipolar I is considered the most severe of the bipolar brain disorders and can produce full-blown manic or depressive stages (or a mixed state of both) for seven consecutive days, often times requiring hospitalisation. Bipolar II generally causes depressive states with some hypomanic states experienced too.

BP-NOS, Bipolar Not Otherwise Specified is a category for individuals who do not really fall into BP I or BP II due to less severe or frequent symptoms. And Cyclothymia is the mild version of bipolar disorder, with the individual experiencing depression and hypomania, but only for about a two year period, according to the National Institute of Mental Health.

Bipolar II and the brain

A 2006 article in the MIT online Technology Review magazine entitled "Finding Bipolar Disorder with MRI" emphasised the inability of traditional magnetic resonance imaging (MRI) equipment at this time to aid in diagnosing bipolar disorder (I, II, or other types) by this particular brain imaging means. But the article also detailed the advances being made in viewing brain function and activity (through functional MRI's) that could later help with diagnosing bipolar disorder, and which help now to monitor brain functioning of those already diagnosed.

Brain area affected

In a study conducted in 2009 by the Department of Psychiatry of the Seoul National University College of Medicine and Institute for Human Behavioral Medicine the brains of individuals with bipolar disorder I and II were viewed using MRI technology. The results of the study showed grey brain matter abnormalities in various regions of the brain for bipolar II, as well as bipolar I participants, although bipolar II had fewer abnormalities. Those with bipolar II had grey matter deficits in the ventromedial prefrontal regions of the brain (located in the rear of the front part of the brain, inside the cortex and atop the orbits of the eyes), and also in the anterior limbic cortices of the brain (an area that spans almost the length of the brain, but is towards the brains outer centre).

Abnormalities explained

The particular brain areas affected with grey matter deficits (ventromedial prefrontal regions and anterior limbic cortices) each affect certain brain functions. The ventromedial prefrontal regions of the brain impact concentration, inhibition, emotions, behaviour and learning. The anterior limbic cortices impact smell, agitation, emotional control and memory.

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About the Author

Holly Huntington's writing has been published online by eHow.