Which of the following is a common sign of mania?

Heightened energy levels are a hallmark symptom of mania, which is characterized by an abnormally elevated mood and increased activity or energy. During manic episodes, individuals often experience an intense surge of energy that may lead to hyperactivity, restlessness, and difficulty sitting still. This increased energy can manifest in various ways, such as overly ambitious projects, lack of need for sleep, and an increased tendency to speak rapidly or engage socially.

In contrast, the other options do not typically align with the symptoms of mania. Increased appetite generally suggests a more depressive state, while excessive sleeping is also associated with depressive episodes or other mood disorders. Decreased self-esteem is more reflective of depressive symptoms as well, rather than the inflated self-esteem or grandiosity often seen in mania. Therefore, heightened energy levels is the clear and defining characteristic of a manic episode.