<p>The exact cause of bipolar disorder is unknown (source: <a href="http://www.nhs.uk/aboutNHSChoices/Pages/ContactUs.aspx" rel="nofollow">NHS</a>). It is believed that there are a number of interacting physical, environmental and social factors that may cause bipolar disorder to develop.</p>

<ul>
<li><strong>Chemical imbalance in the brain</strong>: Bipolar disorder is believed to be the result of chemical imbalances in the brain, and <strong>noradrenaline</strong> has been implicated <a href="http://www.sciencedirect.com/science/article/pii/0006322394912017" rel="nofollow">(Young <em>et al</em>., 1994)</a>. Noradrenalin (norepinephrine) in the central nervous system regulates arousal and modulates reward circuitry and positive reinforcement. Many antidepressant drugs target noradrenergic projections to alleviate symptoms of depression <a href="http://www.sciencedirect.com/topics/page/Norepinephrine" rel="nofollow">(Trevino <em>et al</em>, 2012)</a>. There is evidence that episodes of <strong><a href="http://psychcentral.com/disorders/manic-episode/" rel="nofollow">mania</a></strong> may occur when levels of noradrenaline are too high, and episodes of <strong><a href="http://www.nimh.nih.gov/health/publications/depression-what-you-need-to-know-12-2015/index.shtml" rel="nofollow">depression</a></strong> may be the result of noradrenaline levels becoming too low (source: <a href="http://www.nhs.uk/aboutNHSChoices/Pages/ContactUs.aspx" rel="nofollow">NHS</a>). Reduced serotonin levels have been found too, which is a general hallmark of depression and not specifically related to bipolar disorder <a href="http://www.sciencedirect.com/science/article/pii/0006322394912017" rel="nofollow">(Young <em>et al</em>., 1994)</a>.</li>
<li><strong>Genetics</strong>: bipolar disorder tends to run in families <a href="http://www.sciencedirect.com/science/article/pii/S0140673609600726" rel="nofollow">(Lichtenstein <em>et al</em>., 2009</a>. The family members of a person with the condition have an increased risk of developing it themselves. However, no single gene is responsible for bipolar disorder. Instead, a number of genetic and environmental factors are thought to act as triggers (sources: <a href="http://www.nhs.uk/aboutNHSChoices/Pages/ContactUs.aspx" rel="nofollow">NHS</a> and <a href="http://www.mayoclinic.org/diseases-conditions/bipolar-disorder/basics/risk-factors/con-20027544" rel="nofollow">Mayo Clinic</a>).</li>
<li><strong>Triggers</strong>: A stressful circumstance or situation often triggers the symptoms of bipolar disorder, <em>e.g.</em>, physical, sexual or emotional abuse, or
the death of a close family member. These life-altering events can cause episodes of depression at any time in a person's life. Bipolar disorder may also be triggered by physical illness, sleep disturbances, overwhelming problems in everyday life (sources: <a href="http://www.nhs.uk/aboutNHSChoices/Pages/ContactUs.aspx" rel="nofollow">NHS</a> and <a href="http://www.mayoclinic.org/diseases-conditions/bipolar-disorder/basics/risk-factors/con-20027544" rel="nofollow">Mayo Clinic</a>).</li>
</ul>

<p><sub><strong>References</strong><br>
<strong>-</strong> <a href="http://www.sciencedirect.com/science/article/pii/S0140673609600726" rel="nofollow">Lichtenstein <em>et al</em>., <em>Lancet</em> (2009); <strong>373</strong>(9659): 234–9</a><br>
<strong>-</strong> <a href="http://www.sciencedirect.com/topics/page/Norepinephrine" rel="nofollow">Trevino <em>et al</em>, <em>Encyclopedia of Human Behavior</em> (2012), 2<sup>nd</sup> ed.</a><br>
<strong>-</strong> <a href="http://www.sciencedirect.com/science/article/pii/0006322394912017" rel="nofollow">Young <em>et al</em>., <em>Biol Psychiatry</em> (1994); <strong>35</strong>(2): 121–7</a></sub></p>

CC BY-SA 3.0
2016-09-14T19:20:44.117Z
2016-09-14T19:36:20.920Z
2016-09-14T19:36:20.920Z
AliceD
<p>Many sources claim that bipolar disorder is associated with problems in the homeostasis of excitatory neurotransmitters.</p>

<p>Is this true? What are the leading theories about neurological causes for bipolar disorder?</p>

<neuroscience><bipolar-disorder><etiology>
What is the neurological basis of bipolar disorder?
uhbif19
# What is the neurological basis of bipolar disorder?

(Asked by: username_0 on 2016-09-14)

Many sources claim that bipolar disorder is associated with problems in the homeostasis of excitatory neurotransmitters.

Is this true? What are the leading theories about neurological causes for bipolar disorder?

**Tags:** neuroscience, bipolar-disorder, etiology


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## 1 answers

### Answer by username_1 on 2016-09-14. Score: 4

The exact cause of bipolar disorder is unknown (source: [NHS](http://www.nhs.uk/aboutNHSChoices/Pages/ContactUs.aspx)). It is believed that there are a number of interacting physical, environmental and social factors that may cause bipolar disorder to develop.

* **Chemical imbalance in the brain**: Bipolar disorder is believed to be the result of chemical imbalances in the brain, and **noradrenaline** has been implicated [(Young *et al*., 1994)](http://www.sciencedirect.com/science/article/pii/0006322394912017). Noradrenalin (norepinephrine) in the central nervous system regulates arousal and modulates reward circuitry and positive reinforcement. Many antidepressant drugs target noradrenergic projections to alleviate symptoms of depression [(Trevino *et al*, 2012)](http://www.sciencedirect.com/topics/page/Norepinephrine). There is evidence that episodes of **[mania](http://psychcentral.com/disorders/manic-episode/)** may occur when levels of noradrenaline are too high, and episodes of **[depression](http://www.nimh.nih.gov/health/publications/depression-what-you-need-to-know-12-2015/index.shtml)** may be the result of noradrenaline levels becoming too low (source: [NHS](http://www.nhs.uk/aboutNHSChoices/Pages/ContactUs.aspx)). Reduced serotonin levels have been found too, which is a general hallmark of depression and not specifically related to bipolar disorder [(Young *et al*., 1994)](http://www.sciencedirect.com/science/article/pii/0006322394912017).
* **Genetics**: bipolar disorder tends to run in families [(Lichtenstein *et al*., 2009](http://www.sciencedirect.com/science/article/pii/S0140673609600726). The family members of a person with the condition have an increased risk of developing it themselves. However, no single gene is responsible for bipolar disorder. Instead, a number of genetic and environmental factors are thought to act as triggers (sources: [NHS](http://www.nhs.uk/aboutNHSChoices/Pages/ContactUs.aspx) and [Mayo Clinic](http://www.mayoclinic.org/diseases-conditions/bipolar-disorder/basics/risk-factors/con-20027544)).
* **Triggers**: A stressful circumstance or situation often triggers the symptoms of bipolar disorder, *e.g.*, physical, sexual or emotional abuse, or
  the death of a close family member. These life-altering events can cause episodes of depression at any time in a person's life. Bipolar disorder may also be triggered by physical illness, sleep disturbances, overwhelming problems in everyday life (sources: [NHS](http://www.nhs.uk/aboutNHSChoices/Pages/ContactUs.aspx) and [Mayo Clinic](http://www.mayoclinic.org/diseases-conditions/bipolar-disorder/basics/risk-factors/con-20027544)).

**References**  
**-** [Lichtenstein *et al*., *Lancet* (2009); **373**(9659): 234–9](http://www.sciencedirect.com/science/article/pii/S0140673609600726)  
**-** [Trevino *et al*, *Encyclopedia of Human Behavior* (2012), 2nd ed.](http://www.sciencedirect.com/topics/page/Norepinephrine)  
**-** [Young *et al*., *Biol Psychiatry* (1994); **35**(2): 121–7](http://www.sciencedirect.com/science/article/pii/0006322394912017)


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