[ultramar]

Sorry this is so long, but worth a read when you have the time!

Causes of bipolar disorder per the Mayo Clinic, the National Institute of Mental Health and WebMD respectively.

[Uggh, I just saw that some of the print came out really small and the edit option won't let me change that -I put in some extra spacing to make it at least a little more readable -sorry!].


Causes

By Mayo Clinic staff

The exact cause of bipolar disorder is unknown, but several factors seem to be involved in causing and triggering bipolar episodes:

· Biological differences. People with bipolar disorder appear to have physical changes in their brains. The significance of these changes is still uncertain but may eventually help pinpoint causes.

· Neurotransmitters. An imbalance in naturally occurring brain chemicals called neurotransmitters seems to play a significant role in bipolar disorder and other mood disorders.

· Hormones. Imbalanced hormones may be involved in causing or triggering bipolar disorder.

· Inherited traits. Bipolar disorder is more common in people who have a blood relative (such as a sibling or parent) with the condition. Researchers are trying to find genes that may be involved in causing bipolar disorder.

· Environment. Stress, abuse, significant loss or other traumatic experiences may play a role in bipolar disorder.

Factors that may increase the risk of developing bipolar disorder include:

· Having blood relatives such as a parent or sibling with bipolar disorder

· Periods of high stress

· Drug or alcohol abuse

· Major life changes, such as the death of a loved one

· Being in your early 20s

National Institute of Mental Health

What are the risk factors for bipolar disorder?

Scientists are learning about the possible causes of bipolar disorder. Most scientists agree that there is no single cause. Rather, many factors likely act together to produce the illness or increase risk.

Genetics

Bipolar disorder tends to run in families, so researchers are looking for genes that may increase a person's chance of developing the illness. Genes are the "building blocks" of heredity. They help control how the body and brain work and grow. Genes are contained inside a person's cells that are passed down from parents to children.
Children with a parent or sibling who has bipolar disorder are four to six times more likely to develop the illness, compared with children who do not have a family history of bipolar disorder.12 However, most children with a family history of bipolar disorder will not develop the illness.

Genetic research on bipolar disorder is being helped by advances in technology. This type of research is now much quicker and more far-reaching than in the past. One example is the launch of the Bipolar Disorder Phenome Database, funded in part by NIMH. Using the database, scientists will be able to link visible signs of the disorder with the genes that may influence them. So far, researchers using this database found that most people with bipolar disorder had:13

• Missed work because of their illness
• Other illnesses at the same time, especially alcohol and/or substance abuse and panic disorders
• Been treated or hospitalized for bipolar disorder.

The researchers also identified certain traits that appeared to run in families, including:

• History of psychiatric hospitalization
• Co-occurring obsessive-compulsive disorder (OCD)
• Age at first manic episode
• Number and frequency of manic episodes.

Scientists continue to study these traits, which may help them find the genes that cause bipolar disorder some day.
But genes are not the only risk factor for bipolar disorder. Studies of identical twins have shown that the twin of a person with bipolar illness does not always develop the disorder. This is important because identical twins share all of the same genes. The study results suggest factors besides genes are also at work. Rather, it is likely that many different genes and a person's environment are involved. However, scientists do not yet fully understand how these factors interact to cause bipolar disorder.

Brain structure and functioning

Brain-imaging studies are helping scientists learn what happens in the brain of a person with bipolar disorder.14, 15 Newer brain-imaging tools, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), allow researchers to take pictures of the living brain at work. These tools help scientists study the brain's structure and activity.
Some imaging studies show how the brains of people with bipolar disorder may differ from the brains of healthy people or people with other mental disorders. For example, one study using MRI found that the pattern of brain development in children with bipolar disorder was similar to that in children with "multi-dimensional impairment," a disorder that causes symptoms that overlap somewhat with bipolar disorder and schizophrenia.16 This suggests that the common pattern of brain development may be linked to general risk for unstable moods.
Learning more about these differences, along with information gained from genetic studies, helps scientists better understand bipolar disorder. Someday scientists may be able to predict which types of treatment will work most effectively. They may even find ways to prevent bipolar disorder.

WebMD

Doctors don't completely understand the causes of bipolar disorder. But they've gained a greater understanding in the past 10 years of the bipolar spectrum, which includes the elated highs of mania to the lows of major depression, along with various mood states between these two extremes.
Experts do believe that bipolar disorder often runs in families, and there is a genetic part to this mood disorder. There is also growing evidence that environment and lifestyle issues have an effect on the disorder's severity. Stressful life events -- or alcohol or drug abuse -- can make bipolar disorder more difficult to treat.

Recommended Related to Bipolar Disorder
What Is the Bipolar Spectrum?

The bipolar spectrum is a concept which observes that many people with depression, substance abuse, and other conditions share many of bipolar disorder's symptoms. Under this concept, such people's conditions are in the "bipolar spectrum," without qualifying as true bipolar disorder. Although many psychiatrists find the bipolar spectrum concept useful, it has not yet been adopted widely.

Read the What Is the Bipolar Spectrum? article > >

The Brain and Bipolar Disorder

Experts believe bipolar disorder is partly caused by an underlying problem with specific brain circuits and the balance of brain chemicals called neurotransmitters.
Three brain chemicals -- noradrenaline (norepinephrine), serotonin, and dopamine -- are involved in both brain and bodily functions. Noradrenaline and serotonin have been consistently linked to psychiatric mood disorders such as depression and bipolar disorder. Dopamine is commonly linked with the pleasure system of the brain. Disruption to the dopamine system is connected to psychosis and schizophrenia, a severe mental disorder characterized by distortions in reality and illogical thought patterns and behaviors.

The brain chemical serotonin is connected to many body functions such as sleep, wakefulness, eating, sexual activity, impulsivity, learning, and memory. Researchers believe that abnormal serotonin levels contribute to mood disorders (depression and bipolar).

Is Bipolar Disorder Genetic?

Many studies of bipolar patients and their relatives have shown that bipolar disorder can run in families. Perhaps the most convincing data come from twin studies. In studies of identical twins, scientists report that if one identical twin has bipolar disorder, the other twin has a greater chance of developing bipolar disorder than another sibling in the family. Researchers conclude that the lifetime chance of an identical twin (of a bipolar twin) to also develop bipolar disorder is about 40% to 70%.

In more studies at Johns Hopkins University, researchers interviewed all first-degree relatives of patients with bipolar I and bipolar II disorder and concluded that bipolar II disorder was the most common affective disorder in both family sets. The researchers found that 40% of the 47 first-degree relatives of the bipolar II patients also had bipolar II disorder; 22% of the 219 first-degree relatives of the bipolar I patients had bipolar II disorder. However, among patients with bipolar II, researchers found only one relative with bipolar I disorder. They concluded that bipolar II is the most prevalent diagnosis of relatives in both bipolar I and bipolar II families.
Studies at Stanford University that explored the genetic connection of bipolar disorder found that children with one biological parent with bipolar I or bipolar II disorder have an increased likelihood of getting bipolar disorder. In this study, researchers reported that 51% of the bipolar offspring had a psychiatric disorder, most commonly major depression, dysthymia (mild depression), bipolar disorder, or attention deficit hyperactivity disorder (ADHD). Interestingly, the bipolar parents in the study who had a childhood history of ADHD were more likely to have children with bipolar disorder but not ADHD.
In other findings, researchers report that first-degree relatives of a person diagnosed with bipolar I or II disorder are at an increased risk for major depression when compared to first-degree relatives of those with no history of bipolar disorder. Scientific findings also show that the lifetime risk of affective disorders in relatives with family members who have bipolar disorder increases, depending on the number of diagnosed relatives.

[faerie_moon_x]

Recently, this research came out, which finds that disturbances in the same gene play a role in 5 of mental illness (autism, schizophrenia, bipolar, major depression, and ADHD.) The study followed 60,000 people worldwide, half with diagnosis and half with none. You can read about it here:
http://www.nytimes.com/2013/03/01/he...ders.html?_r=0

Of course, this is just a first step and there will need to be follow-up studies. But I find this very promising and pointing us in the right direciton.