At the time, it seemed to be a medical mystery.was running a clinic in San Diego in the 1980's for the morbidly obese. Under his supervision, many patients lost 200 to 400 pounds -- only to gain it all back again. Or lose the weight then drop out of the program.These results puzzled Dr. Felitti. One day, while interviewing a new patient, he asked her when she'd become sexually active. The patient looked down and said, "four years old". A lightbulb went on. Could childhood trauma trigger not only obesity, but a whole host of psychological and physiological illnesses?The link between early trauma and ill health later was untilled soil in the world of medicine. But the possibility of a connection captured the interest of the Centres for Disease Control and Prevention. And it was the beginning of a 25-year odyssey for Vincent Felitti when he teamed up with researchers to study the health of 17,000 members of a preventive care program at Kaiser Permanente, a private insurer. Beyond routine physicals, workers (mostly middle-class and middle-aged) filled out an extensive trauma questionnaire covering ten categories of abuse, from physical violence to attempted suicide. Past and present health problems were also tabulated. The results were astonishing.The more categories of abuse that participants suffered, the higher their chances of illness were. For example, women who experienced physical violence were 60% more likely to experience depression, compared to 18% for women who reported no categories of abuse. The figures for attempted suicide were even more startling. Only 2% of those who reported no categories of abuse attempted suicide. However, those who reported four or more categories were breathtakingly 1,200% likelier to attempt killing themselves.Similar results for smoking, cancer, diabetes, among other diseases, followed the same pattern. Today, the Adverse Childhood Experiences (ACE) Study has become a fixture in the fields of medicine, psychiatry and pediatrics. Six state legislatures in the U.S. have passed legislation to stimulate the routine collection of data on childhood trauma. And now, the World Health Organization also uses the ACE model to explore global health.