Does how you do depend on how you think you'll do? A systematic review of the evidence for a relation between patients' recovery expectations and health outcomes

BACKGROUND: Most clinicians would probably agree that what patients think will happen can influence what does happen over the clinical course. Yet despite useful narrative reviews on expectancy of therapeutic gain and the mechanisms by which expectancy can affect health outcomes, we were unable to locate a systematic review of the predictive relation between patients' recovery expectations and their health outcomes. METHODS: We searched MEDLINE for English-language articles published from 1966 to June 1998 with a title or abstract containing at least 1 of the medical subject headings (MeSH) 'self-assessment,' 'self-concept' or 'attitude to health,' or the MeSH subheading 'psychology,' and at least 1 word from each of 3 sets: 'patient' and similar words; a form of 'expectation,' 'belief' or 'prediction'; and a form of 'recover,' 'outcome,' 'survival' or 'improve.' Relevant articles contained original research data, measured patients' recovery expectations, independently measured a subsequent health outcome and analyzed the relation between expectations and outcomes. We assessed internal validity using quality criteria for prognostic studies based on 6 categories (case definition; patient selection; extent of follow-up; objective outcome criteria; measurement and reporting of recovery expectations; and analysis). RESULTS: A total of 1243 titles or abstracts were identified through the computer search, and 93 full-text articles were retrieved. Forty-one of these articles met the relevance criteria, along with 4 additional articles identified through other means. Agreement beyond chance on quality assessments of 18 randomly selected articles was high (kappa = 0.87, p = 0.001). Sixteen of the 45 articles provided moderate-quality evidence and included a range of clinical conditions and study designs; 15 of the 16 showed that positive expectations were associated with better health outcomes. The strength of the relation depended on the clinical conditions and the measured used. INTERPRETATION: Consistency across the studies reviewed and the evidence they provided support the need for clinicians to clarify patients' expectations and to assist them in having appropriate expectations of recovery. The understanding of the nature, extent and clinical implications of the relation between expectations and outcomes could be enhanced by more conceptually driven and methodologically sound research, including evaluations of intervention effectiveness