Which symptom is often observed in those diagnosed with Chronic Fatigue Syndrome?

Tender lymph nodes are commonly observed in individuals diagnosed with Chronic Fatigue Syndrome (CFS). This symptom is part of a wider range of physiological indicators that can manifest in CFS patients. The tenderness or swelling of lymph nodes is often attributed to the immune system's response to chronic stress and fatigue.

In CFS, the immune system is believed to be dysregulated, which can lead to feelings of malaise and the sensation of swollen or tender lymph nodes, even in the absence of an acute infection. This symptom is significant because it reflects the complex interplay between fatigue and immune response.

The other symptoms listed, while they may occur in individuals with various health issues, are not as directly associated with CFS as tender lymph nodes are. Nausea can occur but is not a defining symptom, constant cough is more indicative of respiratory issues, and vision changes may occur due to fatigue but do not reflect the characteristic immune dysfunction associated with CFS. Thus, the presence of tender lymph nodes serves as an important clinical sign in understanding the condition of someone suffering from Chronic Fatigue Syndrome.