A patient presents with chronic fatigue, lack of concentration, and low mood. What is a supporting symptom for major depressive disorder?

Diminished interest in activities, also known as anhedonia, is a key supporting symptom of major depressive disorder (MDD). In patients diagnosed with MDD, it is common to see significant decreases in pleasure or interest in activities that they previously found enjoyable. This symptom often accompanies other hallmark features of depression, such as chronic fatigue, difficulty concentrating, and low mood, which the patient is already experiencing.

The presence of diminished interest adds further evidence to the diagnosis of major depressive disorder, as MDD is characterized by a spectrum of emotional and physical symptoms that significantly impact a person's daily functioning and quality of life. In contrast, the other options—excessive energy, hyperactivity, and intense happiness—do not align with the clinical presentation of major depression, as these are more indicative of elevated mood states or manic episodes, which are not associated with the depressive symptomatology the patient is experiencing.