Queensland Institute of Medical Research (QIMR) scientists have identified a new link between strong period pain experienced in adolescence and early adulthood and the risk of endometriosis.Researchers from QIMR's Gynecological Cancer Laboratory have found having strong period pain often at an early age doubles a woman's risk of developing endometriosis.The study also found that girls starting their menstrual cycle after 14 years old had a significantly decreased risk of endometriosis.Researchers analyzed information from more than 500 Australian women ? making this one of the largest studies of its kind.