What are the hallmark features of Bipolar Disorder?

Bipolar Disorder is characterized by significant mood fluctuations that include periods of depression and episodes of mania or hypomania. During manic episodes, individuals may experience elevated mood, increased energy levels, decreased need for sleep, racing thoughts, and impulsive behaviors. Conversely, during depressive episodes, they may feel a persistently low mood, a lack of energy, and a loss of interest in activities. The combination of these mood states—depressive and euphoric—along with the variability in energy levels, is what makes option B the hallmark feature of Bipolar Disorder.

The other options present characteristics that do not align with Bipolar Disorder. Consistent mood stability does not pertain to this disorder, as the defining aspect is the presence of distinct mood episodes. Chronic low energy and persistent mild sadness would be more indicative of a Depressive Disorder rather than the episodic nature typical of Bipolar Disorder. Lastly, option D specifies only experiencing depressive episodes, which would align with Major Depressive Disorder rather than Bipolar Disorder, which requires the presence of manic or hypomanic episodes for diagnosis.