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Bipolar Disorder

Pathology and Types || Epidemiology || Signs and Symptoms || Treatment || Overview || References and Resources || Comment || Search

Pathology and Types

The pathology of bipolar disorder is complex. Like most psychiatric disorders the pathological basis is not yet well understood. There are several different theories all with some supporting evidence.

One theory is that there is disorganized white matter (ie: the connections between neurons) in the brains of patients with bipolar disorder. Imaging studies using MRI have shown subtle changes in white matter compared to healthy patients.

In addition, there appears to be a decreased number of glial cells (the supporting cells of the brain) in specific areas of the brain. Imbalances in neurochemicals may also play a role in the pathology of bipolar disorder, although the exact underpinnings are still widely unknown.

Bipolar disorder has two main types. Type one is characterized by at least 1 period of mania with or without depression. The key distinction is that depressive symptoms are NOT necessary to establish the diagnosis.

Bipolar type 1 = mania ± depression

Type two disorder is characterized by at least 1 period of clinical depression AND at least 1 period of hypomania. Notice that a period of frank manic symptoms is not necessary to establish a diagnosis of type two disorder.

Bipolar type 2 = depression + hypomania



Type 1 bipolar disorder affects roughly 1% of the population. Males and females are equally affected. There is also a very strong familial component to the disease. If you have an identical twin with bipolar disorder you have a 70% chance of developing the disorder yourself! In type 2 bipolar roughly 0.5% of the population is affected.


Signs and Symptoms

Type 1 bipolar disorder presents with symptoms of mania. Mania can be described as a socially detrimental expansive mood. Patients who are manic often need much less sleep than average, are grandiose in their thinking, are sexually promiscuous, spend money excessively, and are often irritable.

Many patients with bipolar have "flight of ideas" thinking and pressured speech (ie: they cant get enough out). These patients are difficult to interrupt verbally because they speak quickly and often jump from topic to topic. Depressive symptoms may or may not be present in type 1 bipolar disorder (they are discussed below).

Type 2 bipolar is characterized by at least one period of depression. Clinical depression is characterized by at least five, or more, of the following criteria lasting for a minimum of two weeks:

(1) Suicidal thoughts/actions
(2) Decreased interest in previously enjoyed activities (aka: anhedonia)
(3) Feelings of guilt
(4) Decreased energy
(5) Decreased concentration
(6) Altered appetite
(7) Psychomotor retardation
(8) Altered sleep patterns
(9) Depressed mood

Type 2 bipolar also requires a period of hypomania, which is a mood state slightly below that of mania. Patients who are hypomanic often function well in society because they have lots of energy. However, the potential danger is that hypomania may turn to mania in a certain subset of the population.



The main treatment for bipolar disorder is mood stabilizing medication. The flagship medication in this category is lithium. Unfortunately, lithium has many side effects and treatment must be monitered closely.

Other classes of medications, namely certain anti-seizure medications such as lamotrigine (Lamictal®) are also used as mood stabilizers.

Acutely manic patients are treated with anti-psychotics like haloperidol (Haldol®, "vitamin H") to get their manic symptoms under control quickly. They are then put on a mood stabilizing medication for long term management. The use of antidepressants in bipolar disorder is controversial because it is believed that they may cause a manic episode. Therefore, antidepressants are typically only given if a patient is also on a mood stabilizer.



Bipolar disorder comes in two flavors: type 1 and type 2. Type 1 bipolar is characterized by an episode of mania with or without depression; type 2 bipolar is characterized by a period of depression with hypomania, mania may or may not be present in type 2 disease. Treatment is with mood stabilization medications like lithium and lamotrigine.


References and Resources

(1) Ongür D, Drevets WC, Price JL. Glial reduction in the subgenual prefrontal cortex in mood disorders. Proc Natl Acad Sci U S A. 1998 Oct 27;95(22):13290-5.

(2) Holland J, Agius M. Neurobiology of bipolar disorder - lessons from migraine disorders. Psychiatr Danub. 2011 Sep;23 Suppl 1:S162-5. Review.

(3) Kato T. Molecular neurobiology of bipolar disorder: a disease of 'mood-stabilizing neurons'? Trends Neurosci. 2008 Oct;31(10):495-503. Epub 2008 Sep 4.

(4) Nusslock R, Frank E. Subthreshold bipolarity: diagnostic issues and challenges. Bipolar Disord. 2011 Nov;13(7-8):587-603.


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