Which of the following is a clinical manifestation of Major Depressive Disorder?

Persistent sadness is a key clinical manifestation of Major Depressive Disorder (MDD). Individuals with MDD often experience a continuous feeling of sadness, hopelessness, or emptiness that significantly impacts their daily functioning and quality of life. This symptom can manifest in various ways, including a lack of interest in previously enjoyed activities, changes in appetite or sleep patterns, and difficulty concentrating. The feeling of sadness in MDD is more than just a fleeting emotion; it is pervasive and can last for extended periods, often leading to functional impairments.

In contrast, the other options represent emotional states that are typically not associated with Major Depressive Disorder. Euphoria suggests an elevated mood, which is the opposite of the depressive symptoms seen in MDD. Increased energy levels may indicate a manic phase in disorders like Bipolar Disorder, rather than depression. Excessive optimism also does not align with the symptoms of MDD, as depressed individuals generally struggle with negative thoughts about themselves and their future. Thus, persistent sadness clearly stands out as a fundamental characteristic of Major Depressive Disorder.