Stomach cancer is mainly related to improper diet of patients, and also related to HP infection, which is Helicobacter pylori infection. If the patient is 20 years old and has gastric cancer, the causes are mainly as follows: 1. Observe whether there is improper diet, such as overeating, irregular eating, etc., and like to eat fried or deep-fried food, which will cause mucous membrane damage to the stomach; 2. Observe whether there is any family history, such as whether there is any history of disease of parents and siblings; 3. Pay attention to whether there is any relationship with the geographical area, such as in the area of high prevalence of gastric cancer, and the soil and water, etc.; 4, also observe whether there is any relationship with HP infection, for example, if the patient is infected with Helicobacter pylori, the chance of stomach cancer will increase. So for young people, don’t overeat, avoid alcoholism, smoking and so on.