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For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.
In women, pharmacodynamic differences include increased sensitivity to (and increased effectiveness of) beta-blockers, opioids, selective serotonin reuptake inhibitors, and typical antipsychotics.
Many people have small pouches in their colons that bulge outward through weak spots. Each pouch is called a diverticulum. About 10% of Americans older than age 40 years have diverticulosis, which, when the pouches become infected or inflamed, is called diverticulitis. The main cause of diverticular disease is a low-fiber diet.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Asthma cases in Americans are about 75% higher today than they were in 1980.