Introduction: The study tested whether four commonly used patient-rated outcomes are explained by only one factor, reflecting a general appraisal tendency of patients.
Method: Quality of life, needs and symptoms were rated by 92 patients in community mental health care at baseline and after 18 months and 6 years follow-up periods. At follow ups treatment satisfaction was also assessed. Scores and change scores were subjected to factor analyses. We then tested which individual items predicted factor scores.
Results: One factor explained between 55% and 66% of the variance of the tested patient-rated outcomes cross-sectionally and longitudinally. Only change scores of treatment satisfaction loaded on a separate factor. Seven items consistently explained more than 80% of the variance of the general factor.
Conclusion: Four important patient-rated outcomes are uniformly and substantially influenced by a general tendency for positive or negative appraisals. This tendency can be assessed more simply than using currently established methods.