About the Author

Mayo Clinic, a not-for-profit institution, is among the world's first and oldest group practices of medicine, dedicated to providing comprehensive diagnosis and effective treatment for complex medical problems in every specialty. With this depth of expertise, Mayo Clinic occupies a unique position as a resource to help people lead healthier lives. Mayo Clinic has published reliable health information for millions of consumers worldwide since 1983. Revenues support Mayo Clinic programs, including education and research.