The causes of irritable bowel syndrome include diet, bacterial infection and mental factors. 1. Diet: If patients consume spicy and stimulating or high protein food for a long time, it may affect the digestive function and easily lead to irritable bowel syndrome. 2. Bacterial infection: If the patient has bacterial infection, it will produce a large amount of toxic substances, which will stimulate the stomach and intestines, and easily lead to irritable bowel syndrome. 3. Mental factors: if the patient is in anxiety or depressed mood for a long time, it will lead to the stomach and intestines can’t perform their functions normally, which will easily cause irritable bowel syndrome. There are many other causes of irritable bowel syndrome, it is recommended to go to the regular hospital in time, after the cause of the disease is clear, under the guidance of the doctor for targeted treatment.