While there are different opinions on the root causes of bipolar disorder, researchers have found that genetic, environmental, and lifestyle factors can significantly increase a person's likeliness of experiencing the disorder, About 50 percent of people diagnosed with the illness have a family member with a mood disorder. Bipolar disorder, therefore, is thought to have a strong genetic component. In most cases, genetic traits influence the behavior of neurotransmitters in the brain, including serotonin, dopamine and norepinephrine. Environmental causes of bipolar disorder often act as triggers. Either causing the person to experience his or her first symptoms or making them worse.