What are the reasons for a baby's long-term diarrhea, and how should it be treated?

Patient's question:

When the baby was five months old, they started having diarrhea, and now that they are more than seven months old, they are still having diarrhea. The doctor has prescribed medication and checked their stool, but it's still diarrhea. What could be the reason?

Doctor's answer:

First, you must maintain a positive and optimistic attitude.