General practitioners' decision making for mental health problems: outcomes and ecological validity.

A major problem in the field of medical decision making is the ecological (external) validity of the results. In a Judgement Analysis study on mental health, vignettes were used to capture the decision strategies of 28 General Practitioners (GPs). Two different decision strategies for mental health problems could be distinguished. Although the results were statistically satisfactory and met the assumptions of Judgement Analysis, it was considered necessary to determine the ecological validity of the vignettes. Video tapes (n = 90) of GP consultations were scored in terms of the units of information (cues) which had been used in the vignette study. Additional data gave access to the judgements of the GPs, which were comparable to the judgements obtained in the vignette study. Results showed that the weights given to the different cues in the vignette study were situated within the confidence interval of the weights from the video study. Thus indicating that the results obtained from the vignette study have ecological validity.