Causes of bipolar disorder
Less is known about the causes of bipolar compared to other severe mental illnesses. In the past, theories have looked at social causes that impact on peoples lives. More recently there have also been studies on biological causes such as genetics and hormones.
According to research done by the National Institute for Clinical Excellence (NICE), there is currently no single explanation for someone developing Bipolar although the following factors are thought to be involved:
Genetics
As mood disorders often effect some families more than others, a lot of attention has been given to the genetic basis for bipolar.
First degree relatives such as parents, children and siblings of a person with bi-polar are 5% - 10% more likely to develop the illness than the rest of the population.
If an identical twin has bipolar disorder, the other twin will also develop it 40-80% of the time. Non-identical twins with less genetic similarities have a 15%-20% chance.
Bio-chemicals
A lot of research has gone into the possible abnormalities in brain function of people with bipolar disorder. Interest has centered on two main areas: the hormonal system and the role of certain brain chemicals:
A number of studies have shown that people with bi-polar produce too much of the stress hormone cortisol. This can have an effect on mood and memory. Furthermore abnormalities of the thyroid hormones are also detected in people with bipolar and this can have a profound effect on behavior and mood.
Studies have also shown that abnormalities exist in the production of dopamine and serotonin chemicals in the brain either producing too much or breaking them down too easily. These brain chemicals also have a role to play in regulating mood as well as sleep patterns.
Environmental factors
As research has shown that the chance of developing bipolar can be shared between some relatives but not all, researchers believe that life events could also play a part.
Evidence shows that there is a link between episodes of manic depression and stressful life events. For example when people with bipolar first become ill they have often experienced significant changes or highly stressful situations beforehand. Subsequent episodes are usually preceded by stressful periods.
Factors such as childhood maltreatment may make someone more susceptible to developing the illness. Abuse and neglect could alter the way the body produces hormones to events later in life.
