Which of the following is often a characteristic of individuals with bipolar disorder?

Individuals with bipolar disorder often experience periods of heightened energy, which are known as manic or hypomanic episodes. During these phases, they may feel unusually euphoric, overly enthusiastic, or exceptionally irritable. This elevated mood is typically accompanied by increased activity levels, a reduced need for sleep, and a sense of invincibility. The contrast between these heightened states and depressive episodes is a hallmark feature of bipolar disorder, making this characteristic critical for diagnosis and understanding the condition.

In comparison to the other characteristics listed, constant low mood, inability to focus, and fear of social interactions do not define bipolar disorder specifically. While individuals with bipolar disorder can experience low moods and may have difficulties concentrating during depressive episodes, these attributes alone do not capture the essence of the disorder's cyclical nature of mood changes. Additionally, fear of social interactions is more indicative of anxiety disorders rather than the core features of bipolar disorder. Therefore, the presence of periods of heightened energy is a defining characteristic of this mental health condition.