On the study finding intercessory prayer ineffective, the interesting result was the finding that those who knew they were being prayed for suffered significantly more complications. One thought, mentioned in the article, is that the information worried the patients, that they thought they must be in bad shape to be the subjects of prayers. Here's another: perhaps it encouraged the patients to think the results were out of their hands -- a thought that can be a comfort, but also a harm, as studies have shown that patients who take responsibility for their care do better. Perhaps both effects work together to significantly demoralize patients.

Indeed, perhaps what the other patients were told -- that they might be prayed for, or might not -- rather than being neutral, put them on alert!