What is truth?” Pontius Pilate posed that famous question prior to handing Jesus over to the Jews for execution.
Truth can mean different things to different people. But basically, Jesus Christ taught that God’s Word is truth. He also spoke of himself as “the truth.” And the apostle John wrote: “The truth came to be through Jesus.” (John 1:17) The entire body of Christian teachings, which later became part of the Bible, are therefore also called “the truth of the good news.” (Galatians 2:14) These Christian teachings embody such things as God’s personal name, God’s Kingdom, the resurrection, and Jesus’ ransom.
Having questioned religion on a personal basis, I found that many things taught by some religions are not found in the Bible,so refering back to the OP, some religions do cause harm.
For example, nowhere does it say in the Bible, do not use physicians, in fact at Luke 5 v 31 Jesus mentioned that the healthy do not need a physician but the ailing do.
So these so-called religions that claim faith will heal them are not actually following Bible teachings. Faith alone cannot heal a terminally ill person, it may help the spirit but not the body.