What Are the Causes of Bipolar Disorder?

 Bipolar disorder is a difficult illness to manage and to treat.
Many who have it may ask themselves,Why me? What caused all this?
There are great disagreements as to the causes of bipolar disorder.
They all tend to go back to the old nature/nurture controversy. In
other words, does a thing happen to a person because of who he or she is, or because of the environment he or she grew up in?
The nature side of bipolar disorder causes has always been seen in
family histories. This, however, can be misleading. Families often pass
behaviors on from one generation to the next, regardless of whether
family members are natural relatives or adopted ones.

The scientific concept of correlation without causation may account for
shared histories of bipolar disorder in biologically unrelated
siblings. This concept is easy to grasp. For example, a man could state
that all summer, every time he got a sunburn he ate fish. So, did the
sunburn cause the man to eat fish? No, but the act of fishing both
caused the man's skin to burn and allowed him to catch a fish, which he then ate. In a similar way, bipolar disorder can occur in families
without anything in one family member's bipolar disorder causing the
bipolar disorder of another.

Also, for whatever reason, people with bipolar disorder are often drawn
to each other. In this case it is unclear whether the families formed
come together because of their shared genetically similar
predisposition towards bipolar disorder, or whether some members of the families are genetically more prone to bipolar disorder but the illness
of some other members of the family becomes exaggerated more than it
would in another environment.

Research into the genetic causes of bipolar disorder is often done
using twin studies. It is assumed that twins will have environments
that are as close as is possible. Identical twins are used to show the
effects of genetics, since they will share the same genetic materials.
Fraternal twins are used as a control group. While these twins share
nearly identical environments with their twins, the fraternal twins
have less genetic material in common.
It has been shown through these twin studies, and other studies where
identical twins are compared to adopted siblings, that there does seem
to be a genetic basis for bipolar disorder. Only one percent of the
population has bipolar disorder. Fraternal twins, who share some
genetic information, are 20 percent more likely to have the disease if
one has it. The percentage for identical twins is even higher, at
around 60 to 80 percent chance of one having it if the other does.
Environmental causes of bipolar disorder are more difficult to assess.
Bipolar disorder has been proven to have a chemical basis in the brain,
but the chemical reactions can be caused by any number of factors. A
history of losses early in life can be a contributing factor, as can
any major source of stress. Physical illnesses such as cancer and
others can lead to a depressive state, which is then often followed by
mania.
Neither genetics nor environment can fully explain the causes of
bipolar disorder. Research is constantly being undertaken in both
areas. In the meantime, the nature/nurture controversy is just
beginning to heat up.