There is no known definitive cause of bipolar disorder, but there are several factors that may predispose a person to develop bipolar disorder, including genetics and certain neurobiological characteristics. Bipolar disorder is more likely to emerge in individuals that have immediate relatives with the disorder, such as a parent or sibling. It is unclear whether bipolar disorder is hereditary, but studies have shown that there is a link between genetics and bipolar disorder. Imbalances in brain chemistry or hormones are also known to have a role in the emergence of bipolar disorder, as well as environmental triggers like trauma or abuse.