A placebo (/pl?'sibo?/ pl?-SEE-boh; Latin placebo, "I shall please"[2] from placeo, "I please")[3][4] is a simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient. Sometimes patients given a placebo treatment will have a perceived or actual improvement in a medical condition, a phenomenon commonly called the placebo effect
From wikipedia- Placebo
The belief in God is simply a self-administered placebo. Might make you feel better even though it's false.