While the causes of bipolar disorder are unknown, there are several causes of bipolar disorder, and family history is one of the risk factors. Research suggest that persons whose relatives have the condition have a 10% increase in the risk of developing bipolar disorder.
Consider the following:
A child whose parent has bipolar disorder has a 15 to 30% chance of developing the condition.
If both parents have bipolar disorder, the risk increases to between 50 and 75%.
If one child has bipolar disorder, the risk of another child developing the condition is 15 to 25%.
If one twin has the condition, there is a 40 to 70% chance the other one will get it.
Overall, genetic factors are responsible for 60 to 80% of the cases of bipolar disorder.
However, it is rare for health practitioners to find families where bipolar disorder affects several members across generations. Most cases are isolated, with the disorder affecting only one member of the family. Further, it is possible that environmental factors such as stress and abuse increase the risk of developing the condition.