Final answer:
The decrease in peptic ulcer disease in the US is primarily due to decreased Helicobacter pylori infection. Stress, changes in diet, and antacid overuse are not direct causes of peptic ulcers.
Step-by-step explanation:
The main reason for the decrease in peptic ulcer disease in the US is b) Decreased Helicobacter pylori Infection. Peptic ulcers are mainly caused by infection with the bacterium Helicobacter pylori, which can be transmitted through contaminated food, water, or saliva.
Prior to the discovery of H. pylori as a major cause of peptic ulcers, it was believed that factors such as stress, diet, and the chronic use of non-steroidal anti-inflammatory drugs (NSAIDs) played a larger role in ulcer development. However, it was later found that these factors, while potentially exacerbating an existing ulcer, do not directly cause ulcers.
It is important to note that while H. pylori infection has decreased, it still remains a significant cause of peptic ulcers, and proper treatment with antibiotics is essential to prevent recurrence.