Bipolar Disorder: What is causing this mysterious disorder?

One minute you are overly happy and outgoing believing you can do anything you put your mind to but the next you feel tired, worried, and unexcited about all of the activities you once enjoyed. These polar opposite feelings are commonly experienced by people with bipolar disorder. In my neurochemistry class this week we investigated a possible cause for the mood cycling associated with bipolar disorder. After better understanding bipolar disorder we addressed other issues surrounding the disease. Before I explain the new research regarding a possible cause, I would like to briefly expand on what bipolar disorder is.
Bipolar disorder is a disease characterized by mood cycling between periods of depression and excessive excitement called mania. Mania is commonly described as feeling overly happy or excited, having unrealistic beliefs in one’s own ability, experiencing racing thoughts, and being restless. Depression is when one feels sad, worried, helpless, and lonely for extended periods of time. Bipolar disorder can be diagnosed under two categories depending on the level of mania and depression. Bipolar 1 is characterized by having one or more manic episodes but a depression episode is not required.  Bipolar 2 is diagnosed when someone has one or more depressed episodes, one or more hypomanic episodes, but no manic episodes. Hypomanic episodes are less severe manic episodes characterized by unexplained happiness.
One of the most difficult parts of treating bipolar disorder is that scientists don’t really know what is causing the disease. However, recent research seems to imply that a biological cascade, called the arachidonic acid cascade, might be a significant piece of the bipolar disorder puzzle. Arachidonic acid is a molecule cut out of lipids in the lipid bilayer membrane surrounding our cells. According to the research paper, arachidonic acid is important in the brain because it influences the release of neurotransmitters and gene transcription. However, when too much arachidonic acid is produced it can cause damage to neurons (brain cells). The researchers think that when too much arachidonic acid is produced the mania-like episodes are triggered. Unfortunately the relation between arachidonic acid and depression was not clearly identified. Additionally, I would like to note that the arachidonic acid hypothesis is not the only possible cause for bipolar disorder. There are two others called the GSK-3 inhibition hypothesis and the myo-inositol hypothesis but these were not focused on in the paper.
Finally, the arachidonic acid cascade hypothesis agrees with the present-day treatments for bipolar disorder. The most common type of drug used for the treatment of bipolar disorder is mood stabilizers. Common mood stabilizers include lithium, valproate, and carbamazepine. These mood stabilizers are thought to work by limiting the production of arachidonic acid either by inhibiting the neurotransmitter receptor or the enzymes associated arachidonic acid fabrication. Although these drugs have been relatively successful, bipolar disorder is still not completely understood. Therefore, additional research is needed to better understand what is truly going on in bipolar disorder and what the best ways to fix the problems are.
Source:
1)      http://www.nimh.nih.gov/health/publications/bipolar-disorder/what-are-the-symptoms-of-bipolar-disorder.shtml