Final answer:
Bipolar disorder, formerly called manic depression, is the mental disorder characterized by alternating periods of depression and elation. It is a mood disorder that requires treatment and can greatly affect daily functioning.
Step-by-step explanation:
The mental disorder that results in alternating periods of depression and elation is known as bipolar disorder. Bipolar disorder was previously referred to as manic depression due to the characteristic swings between manic (elation) and depressive episodes. Those with bipolar disorder can experience dramatic shifts in their energy, mood, and ability to function in day-to-day activities. It is a long-term illness that, like depression, requires treatment.
The treatment options may include psychotherapy, medication, and in some cases, other interventions such as electroconvulsive therapy. This disorder is one of several mood disorders which are a leading cause of illness-related hospitalization in the United States. During the depressive phase, individuals may experience feelings of sadness, hopelessness, and low energy, while during the manic phase, they may feel excessively happy, energetic, and impulsive.