Gastric, or gastritis, is caused primarily by inflammation of the stomach lining. The main causes include:

• Infection by the bacterium Helicobacter pylori (H. pylori), which is common worldwide and can cause both acute and chronic gastritis.
• Regular use or overuse of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and aspirin, which chemically erode the stomach lining.
• Excessive alcohol consumption that irritates and breaks down the stomach lining.
• Stress and severe physiological stress (due to surgery, injury, or severe illness), which can reduce blood flow to the stomach lining and increase acid secretion.
• Autoimmune conditions where the body's immune system attacks the stomach lining.
• Other factors such as eating irregularly, consuming spicy or acidic foods, bile reflux, and certain medical conditions like Crohn's disease, viral infections, and parasitic infections.

These causes allow digestive acids to damage the protective mucus layer of the stomach, leading to inflammation, irritation, or erosion, which causes gastric symptoms like pain, bloating, nausea, and indigestion. If untreated, gastritis can lead to complications such as ulcers, bleeding, or increased risk of stomach cancer.