Parenting programmes like The Incredible Years have been proven to have good short-term effects but little research has been done into their long-term effectiveness or into what makes them effective, or not, in children diagnosed with 'conduct disorder' and 'oppositional defiant disorder.' Researchers from the Norwegian University of Science and Technology studied 54 children who had taken part in The Incredible Years programme following them up five or six years afterwards to see how they were getting on. 5-6 years later two-thirds of the children no longer had a diagnosis of 'conduct disorder' or 'oppositional defiant disorder.' The strongest predictors of whether children still had a diagnosis were if they lived only with their mother or if they were a girl.
Drugli, May Britt ... [et al] - Five-to six-year outcome and its prediction for children with ODD/CD treated with parent training Journal of Child Psychology and Psychiatry May 2010, 51(5), 559-566