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Jack Howell (THES, January 19) suggests that an alternative therapy is not invalidated if it improves a medical condition by "the placebo effect".

This contradicts his earlier view that a double-blind, placebo-controlled trial can show such a treatment to be ineffective. The root of this dilemma is that the design of clinical trials is scientifically bogus for disease states based partly on psychosomatic and symptom-perceptive mechanisms. As Roger Greenberg and Seymour Fisher have shown for Prozac, much conventional medicine depends on body-mind interactions. These vary with the person. Therefore therapies have to be evaluated by cognitive methods yet to be recognised by medical research. Until they are, not only will the NHS have problems with complementary medicine but much public health will fail.

David Booth

School of psychology, University of Birmingham