Observational Study Results Aren’t Much Different Than Randomized Controlled Trials

For many years it has been claimed that observational studies find stronger treatment effects than randomized, controlled trials. A meta analysis compared the results of observational studies with those of randomized, controlled trials.

That analysis found little evidence that estimates of treatment effects in observational studies reported after 1984 are either consistently larger than or qualitatively different from those obtained in randomized, controlled trials.