I was at a talk recently regarding the side-effects of a widely used drug, let us call it 'fictoxetine'. Now fictoxetine has long been thought to cause damage to the body, let us say the retina, leading to progressive visual loss and eventually blindness. Fictoxetine can be used for years, even decades, and so patients need to have their vision screened regularly. This talk reported their findings from a systematic review and meta-analysis that sought to find out whether the evidence actually supported this fear.
What they presented was data showing that over 1-2yrs of fictoxetine use visual acuity declined by around 10%. They also reported evidence that found that rates of fictoxetine use in people on a register of blind people were around twice those in the general population. They then concluded from this that fictoxetine doesn't really have as much of a major effect on vision as we had thought so we shouldn't be so worried about it and pontificated on how this myth had become so widespread in the medical community.
The majority of people at that talk took this message at face value and went away with that in their heads, maybe they will change their clinical practice - after all a respected academic in the field of fictoxetine research presented the evidence that showed fictoxetine doesn't have much effect on vision. Didn't he?
Well no, he didn't, the data I've just described is consistent with fictoxetine having really quite a large and serious effect on vision. If the short-term deficits of 10% in acuity over 1-2yrs continued over 10 years that would be a major loss of 40% of visual acuity. The blind register data is neither here nor there, most people would stop fictoxetine in patients with significant visual loss in the hope that they would never reach complete blindness (conversely, maybe they would be more happy to start it in people who were already completely blind than those with some vision). So the data doesn't support the narrative being given to it but few people feel qualified or confident to gainsay a big name in the field.
And this is true throughout academic medicine, and academia in general, powerful personalities are able to shape the discourse in a scientific field not only through the research they perform but also the wider influence their ideas and opinions carry.