Genetic factors in Bipolar Disorder
Bipolar disorder tends to be familiar, meaning that it “runs in
families.” About half the people with bipolar disorder have a
family member with a mood disorder, such as depression. A
person who has one parent with bipolar disorder has a 15 to
25 percent chance of having the condition. A person who has
a non-identical twin with the illness has a 25 percent chance
of illness, the same risk as if both parents have bipolar
disorder. A person who has an identical twin (having exactly
the same genetic material) with bipolar disorder has an even
greater risk of developing the illness about an eightfold
greater risk than a nonidentical twin. A study of adopted