Mats Fridell is one of the leading Swedish researchers on the psychology of abuse. His main question is how to match different kinds of patients with different models of treatment, and how to make the organizational context of the treatment maximally effective. In his research he is following drug addicts who have been treated in Sweden during the years 1977-1995, to see how background data, clinical data, diagnoses, treatment data and motivation can be used to predict outcome at short-term intermediate term (5 years) and long term (15 years follow-up). He has also done systematic literature reviews on psychological treatment for drug abusers.