Paula Ruttle, Concordia University (IMAGE) Concordia University Caption Paula Ruttle studied the relationship between cortisol levels in young people with problematic behaviour such as aggression or depression. Credit Concordia University 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.