yes...I do not trust the claims of any single observational study. Using observational studies is necessary to help understand a problem in preparation for well

yes...I do not trust the claims of any single observational study. Using observational studies is necessary to help understand a problem in preparation for well-conducted large randomized clinical trials (RCTs). Sometime RCTs are not ethical or feasible (like etiological studies of cancer), and then we need many observational studies in different settings and using different designs showing a large effect that cannot be explained by known or unknown confounders and supported by many experimental studies (e.g., in cells). And even then we accept the results on the principle that is better to be safe than sorry. Many observational studies claimed that HRT protect women from heart disease until the definitive trial was done and it was found HRT actually increases the risk of heart disease!! Hundreds of other examples exist of well-researched and widely accepted hypotheses that turned out to be false in RCTs. For every observational study that claims X causes Y, I could find one that claims that X protects against Y, that X has nothing to do with Y, that Y causes X, that there is no X and no Y.. etc. It is the Wild West of science.