It's a guess. You can easily refute it by naming a few studies that show that prayer works.
Prayer 'no aid to heart patients'
Therapies such as prayer and homeopathy are widely used, although past studies looking at the impact of care on patients' health have had mixed results.
The results of this study contradict earlier findings from the same team which suggested a drop of a quarter or more in "adverse outcomes" - including death, heart failure or heart attack.
Your guess seems to be wrong.