Erik Pettersson (IMAGE) Karolinska Institutet Caption Erik Pettersson, researcher at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Sweden. Photo: Gunilla Sonnebring Credit Gunilla Sonnebring Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.