Experts believe bipolar disorder is partly caused by an underlying problem with specific brain circuits and the balance of brain chemicals called neurotransmitters. Three brain chemicals -- noradrenaline (norepinephrine), serotonin, and dopamine -- are involved in both brain and bodily functions.octors don't completely understand the causes of bipolar disorder. But they've gained a greater understanding in recent years of the bipolar spectrum, which includes the elated highs of mania to the lows of major depression, along with various mood states between these two extremes.