The causes of bipolar disorder are thought to be a combination of genetic factors, biological features, and environmental factors. It is more common in those who have a family member with the disease, suggesting some genetic components. Research also shows that imbalances in neurotransmitters or hormones that affect the brain can contribute to the disorder. Various life events such as abuse, mental stress, loss of loved ones, or other traumatic events may trigger the disorder in a susceptible person.