How Depression Can Cause Headaches

Why: "The cause of headaches is frequently psychological, including depression, anxiety, worry, and stress," neurologist Michael Sellman says. About 18 percent of people with migraines have major depression, according to the American Headache Society. Depression is considered a systemic (whole-body) disease.

What to notice: Continuous headache -- lasting for months or years -- and not responding to pain relievers is a red flag for depression, especially in subtle cases, according to Seymour Diamond, founder of Chicago's Diamond Headache Clinic. Familiarize yourself with the warning signs of depression, including changes in sleep or eating patterns and persistent sad or empty feelings.