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Types of bipolar disorder

Episodes of mania and depression typically recur across the life span. Between episodes, most people with bipolar disorder are free of symptoms, but as many as one-third of people have some residual symptoms. A small percentage of people experience chronic unremitting symptoms despite treatment.

The classic form of the illness, which involves recurrent episodes of mania and depression, is called bipolar I disorder. Some people, however, never develop severe mania but instead experience milder episodes of hypomania that alternate with depression; this form of the illnessm is called bipolar II disorder. When four or more episodes of illness occur within a 12-month period, a person is said to have rapid-cycling bipolar disorder. Some people experience multiple episodes within a week, or even within a single day. Rapid cycling tends to develop later in the course of illness and is more common among women that among men.

How is bipolar disorder caused?

Most scientists believe that psychiatric disorders are usually the produces of multiple interacting causal factors. Studies of significant causes and processes in the development of mental illness have found physical, mental, enviornmental and emotional causes for mental illness.

genetic causes

Because bipolar disorder tends to run in families, researchers have been searching for specific genes, passed down through generations that may increase a person's chance of developing the illness. The evidence that heredity plays a role in the development of some forms of mental illness has been discovered by studying identical twins who were raised seperately and studying adopted children of mothers with different forms of severe mental illness and comparing them to non-identical twins raised separately and the general public.

Studying twins has confirmed the major role that genetics plays in the development of manic depression. For example, if an identical twin has manic depression, the other twin will also develop it 40-80% of the time. With non-identical twins, when one twin is affected the chance of the other twin developing the condition is 15-20%. Close relatives such as parents, children and siblings (first-degree relatives) have a 5-10% chance.

However, exactly what is inherited? The neurotransmitter system - the chemical messenger system of the body - has recieved a great deal of attention as a possible cause of bipolar disorder. Researchers have known for decades that there is a link between neurotransmitters and mood disorders, because drugs which alter these transmitters also relieve mood disorders. Some studies hypothesize that a low or high level of a specific neurotransmitter such as serotonin, norepinephrine or dopamine is the cause. Others indicate that an imbalance of these substances is the problem. Still other studies have found that the a change in the sensitivity of the receptors on nerve cells that receive the neurotransmitter messages is at least part of the cause of bipolar disorder.

psychological causes

The main psychological cause that can lead to the onset of symptoms of bipolar disorder is stressful life events. These can range from a death in the family to the loss of a job, from the birth of a child to a move. Stresses and strains may be different for one person to another.

Tags: Bipolar Disorder

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www.rethink.org
Rethink is the largest severe mental illness charity in the UK. We are dedicated to improving the lives of everyone affected by severe mental illness, whether they have a condition themselves, care for others who do, or are professionals or volunteers working in the mental health field.