Chronic diseases have become an increasing portion of modern medicine in the Western world and the goals for treatment are not only to relieve symptoms and their influence on daily life for patients but also to avoid long term complications of the disease and of the treatment given.

The rules for obtaining evidence of the benefit of a new treatment have been widely accepted, with the randomised controlled study as the “gold standard”. Such studies give some guarantee of the effect of a given treatment modality. The possible long term side effects however cannot be secured against in studies carried out over a few months, the usual length of a controlled trial.

The natural history of a chronic disease—how will the disease proceed if no medical intervention is carried out—should ideally be the background for any therapeutic trial. For the immediate short term course, the placebo arm of a controlled study is sufficient. Knowledge of the long term natural course of the disease however does not exist as both the medical profession and patients themselves have continuously interfered and tried to relieve the consequences of the disease. Gradually therefore, the meaning of “natural course” has changed to “the course of the disease when treated in accordance with established and …