Which of the following is a key sign of major depressive disorder?

The key sign of major depressive disorder is the loss of interest in daily activities, known as anhedonia. This symptom reflects a profound decrease in motivation and pleasure for activities that were once enjoyable or engaging. Individuals with major depressive disorder often find it challenging to participate in their usual routines and hobbies, leading to significant impairments in social, occupational, and other important areas of functioning.

This symptom is critical for diagnosis, as it not only highlights the emotional state of the individual but also impacts their overall well-being and quality of life. The presence of anhedonia can manifest in various ways, such as withdrawal from social interactions, a decline in work performance, and diminished enthusiasm for previously loved activities.

In contrast, the other options depict scenarios that are not characteristic of major depressive disorder. Increased energy levels and improved sleep patterns are generally associated with uplifted mood states or may occur during recovery from depression, while heightened cognitive clarity is typically seen in elevated moods, such as those present in hypomania or mania rather than in major depressive disorder. These contrasting symptoms provide a clearer understanding of the nature of depression and its impact on daily functioning.