Etiology for Bipolar Disorder The Brain and Bipolar Disorder Experts believe bipolar disorder is partly caused by an underlying problem with the balance of brain chemicals called neurotransmitters. Three brain chemicals -- noradrenaline (norepinephrine), serotonin, and dopamine -- are involved in both brain and bodily functions. Noradrenaline and serotonin have been consistently linked to psychiatric mood disorders such as depression and bipolar disorder. Serotonin is connected to many body functions such as sleep, wakefulness, eating, sexual activity, impulsivity, learning, and memory. Researchers believe that abnormal serotonin levels contribute to mood disorders (depression and bipolar). Dopamine is commonly linked with the pleasure system of the brain. Disruption to the dopamine system is connected to psychosis.
Epidemiology for Bipolar Disorder Bipolar disorder affects men and women equally, as well as all races, ethnic groups, and socioeconomic classes. Bipolar disorder often develops in a person's late teens or early adult years. At least half of all cases start before age 25. However, some people have their first symptoms during childhood, while others may develop symptoms late in life.