It's a known fact that worry and stress are bad for your ticker, but scientists have finally quantified just how bad. An aggregate of six studies reveals that being stressed out can raise your risk of having a heart attack by 27%—which is the equivalent to smoking five cigarettes a day. Researchers say stress can cause high blood pressure and a 2.8 mmol/L increase in bad LDL cholesterol, which is double the cholesterol levels recommended for heart and stroke patients. This significantly affects the likelihood of a heart attack, as high blood pressure can cause blood vessels to harden and become more easily blocked, and high cholesterol makes the heart work harder to pump blood through narrowed blood vessels. High blood pressure is thought to contribute to 50% of all heart attacks and strokes. The link between stress and heart attacks was greater in older subjects, and was not influenced by gender. A recent study found that stress itself, like smoking, may also be addictive.