The answer is lithium salts are effective dealing of bipolar disorder but not in unipolar depression. Scientists have expanded understanding into why lithium salts are effective at handling bipolar disorder in what could lead to more targeted therapies with fewer side-effects. Bipolar disorder is characterized by alternating states of elevated mood, or mania, and depression. The unipolar connotes a difference between major depression and bipolar depression, which refers to an oscillating state between depression and mania.