Which of the following is a defining characteristic of pediatric bipolar disorder?

The defining characteristic of pediatric bipolar disorder is frequent mood swings with irritability. This disorder in children is often marked by episodes that can switch from extreme excitement or euphoria (mania) to deep sadness or depression, frequently accompanied by irritability. Unlike adults, children with bipolar disorder may exhibit more noticeable irritability during manic episodes rather than euphoria.

The presence of frequent mood swings captures the core symptomatology of pediatric bipolar disorder, distinguishing it from other mood disorders or typical childhood behavior. These extreme shifts can significantly disrupt a child's daily functioning, making early identification and intervention crucial.

While consistent low energy might suggest underlying depression, and occasional mood fluctuations could be considered within the normal range of childhood development, they do not adequately capture the intensity or frequency required for a diagnosis of bipolar disorder. Finally, complete emotional stability is not aligned with the nature of bipolar disorder, as the condition is defined by its instability and extremes in mood.