Faulty logic

“A study shows!”

If a single study shows that there is a good or bad effect of an intervention, it does not mean that is the final answer.

Often there may be more than one study that compares the same intervention, and the results may be different. This can happen for a variety of reasons, such as the studies were small, because the environmental (or other) conditions varied between studies, because the comparisons were more fair or less fair in the different studies, or because they were small studies with few individuals or sites (or events.)

BEWARE if a claim about intervention effects is based on a single study.

REMEMBER: Think about whether there are other studies that compare the same intervention, or whether there is a systematic review of all the relevant studies.