Lessons in how to ruin a study in psychotherapy effectiveness: a critical review of the follow-up study from Chestnut Lodge.

The principal publications from the follow-up study of former patients at Chestnut Lodge are reviewed and critiqued. Originally, the follow-up study was intended as a study of the psychotherapeutic process and its outcome. While widely referred to as a follow-up study, it is not possible to make conclusions about psychotherapy from the study. Data about the psychodynamic aspects of therapy have been collected but never analyzed. Additionally, the study does not fulfill the requirements of a psychotherapeutic outcome study. The conclusion of the current review is that as the study turned out, it only allows one to draw conclusions about different kinds of illness courses and predictor factors.