Genetics - some small twin studies have indicated that there is a genetic contribution to bipolar disorder risk. People with a blood relative who has bipolar disorder have a higher risk of developing it themselves.
Biological traits - experts say that patients with bipolar disorder often show physical changes in their brains. Nobody is sure why the changes lead to the disorder.
Brain-chemical imbalance - neurotransmitter imbalances play a key role in many mood disorders, including bipolar disorder.
Hormonal problems - hormonal imbalances might trigger or cause bipolar disorder.
Environmental factors - abuse, mental stress, a “significant loss,” or some other traumatic event may contribute to bipolar disorder risk.