Which is a common cause of functional constipation in children?

Functional constipation in children often occurs due to behavioral issues related to toilet training, which is why the choice about toddlers during this phase is considered a common cause. During toilet training, children may intentionally withhold bowel movements due to anxiety or discomfort related to the process, leading to the development of constipation. This behavior can create a cycle of withholding, as the longer a child holds their stool, the harder it becomes, making them less likely to want to go.

In contrast, the other options refer to medical conditions that can lead to constipation, but they are less common causes in the general population of children. Cystic fibrosis and Hirschsprung's disease are associated with specific physiological disruptions that cause constipation, while neurological diseases can impact bowel function. However, these conditions are less frequently observed compared to the typical behavioral component involved during toilet training in toddlers, making the toilet training phase a more prevalent influence on functional constipation in children.