Background: 'Relapse' is a common outcome indicator in intervention studies in schizophrenia. In community studies it is frequently equated with hospitalisation and in psychopharmacological studies with predetermined symptom scores. Its clinical meaning, however, remains undefined.
Method: Consensus on the defining features of 'relapse' in schizophrenia used by academic and clinical schizophrenia experts in the UK, was investigated using a four stage Delphi process. A two panel, four stage, Delphi based methodology was used to investigate the implicit meanings of 'relapse' in clinical practice. A multidisciplinary panel of twelve members each listed anonymously ten indicators of relapse. A second panel, of ten experienced psychiatrists, rated the 188 submitted indicators from essential-unimportant (1-5). This panel completed a one day workshop during the remaining Delphi rounds ending with a structured discussion of the results.
Results: Very strong consensus was achieved on the relative importance of potential relapse indicators. There was complete agreement about some aspects of a definition of relapse (such as recurrence of positive symptoms) and a number of the complex issues underlying the concept were clearly articulated.
Conclusions: This four stage Delphi process achieved consensus on core features of relapse. The elucidation of the "softer" features at the threshold between normal fluctuations in functioning and the start of relapse require continuing investigations.