A practitioner's guide to developing critical appraisal skills: observational studies.

BACKGROUND

and Overview. Observational investigations provide an opportunity to document the distribution of diseases in various populations and to explore correlations between exposures and outcomes. Interpreting such correlations as causal is challenging and can lead to more harm than good when used as a basis for advising lifestyle changes or interventions to healthy people. The aim of this review is to provide a brief introduction to observational study designs and describe some of their strengths and weaknesses.

CONCLUSIONS AND PRACTICE IMPLICATIONS

Observational findings can be useful to guide clinical research, but often they do not provide a reliable basis for clinical decision making. Caution in applying observational findings to clinical practice is particularly important when caring for healthy people.