Methodological issues in tardive dyskinesia research.

Research into tardive dyskinesia, an involuntary movement disorder secondary to chronic neuroleptic treatment, has so far produced conflicting results with no clear clinical applications. Heterogeneous diagnostic criteria, research designs, and rating scales, plus an emphasis on single-drug trials, are probably responsible. A strategy of developing pharmacological response profiles for patients participating in tardive dyskinesia research is suggested as one way to produce meaningful data, which may delineate pharmacological and clinical subtypes that would respond to different treatment approaches. Further suggestions are made about future trends in this area of research.