According to a study published in the journal Stroke, coffee and vigorous sex (as well as being startled or angry) can be up the incidence of brain aneurysms in people who have already suffered from brain aneurysms in the past. Why? Aneurysms are the result of the wall of an artery weakening, bulging, and, worst case- bursting. Seems a raise in blood pressure is the root cause. The advice: if you've had an aneurysm, avoid caffeine, and keep your sex low key.