Social media chatter by clinical trial patients has pharmaceutical manufacturers on edge. The Wall Street Journal reports that patients are sharing a plethora of information about their clinical trial experiences, from how to get picked, to seeking out third-party tests that can help patients figure out if they are in the placebo group or part of the crowd receiving the experimental medication.

The Journal notes that the FDA does not have a gag rule for clinical trial participants, but Pfizer’s head of clinical innovation, Craig Lipset, wrote in an op-ed piece that over-sharing could be a problem because patients “could effectively chill a new drug before it ever gets to patients by misinterpreting early signals.” Neuralstem CEO I. Richard Garr tells the Journal it can also influence how other patients are feeling, which can influence results.

Companies are looking for balance, and the Journal notes that Vertex asked patients to limit clinical trial discussions to family members, friends and doctors, and that Shire created a video that shows how one patient’s public discussion about side effects could persuade another patient to drop out of a study.