Which of these is most often associated with an eating disorder?
depression or infection?

Depression

Explanation:

Eating disorders are characterized by a persistent change in the eating process, which leads to changes in food consumption or absorption to the point of impairing one's health and psychological and social functioning. For this reason, it is not uncommon for people with depression to develop some eating disorder, such as other harmful behaviors in their body.

Depression is a condition characterized by intense discouragement, sadness, or a distinct "depressive mood," which people describe as unlike anything they have ever felt. In this state, the appetite may also be altered, with lack (anorexia) or excess, respectively with weight loss and gain.