According to a story in The New York Times, "Prayer by strangers had no effect on the recovery of people who were undergoing heart surgery, a large and long-awaited study has found."
The study was conducted for nearly a decade, involving more than 1,800 patients. Whether or not the patients were prayed for, or even if they knew they were being prayed for, it did not speed up their recovery.
It's one of the most popular studies skeptics have used to say, "See? Prayer doesn't work!" But those skeptics, and those who conducted this study, don't understand how prayer works. There are qualifications for prayer.
Psalm 66:18, "If I'd cherished iniquity in my heart, the Lord would not have listened to my prayer." James 4:3, you ask and do not receive because you ask wrongly. John 14:6 says that Jesus is the only way to the Father, and 1 Timothy 2:5 says he's the only mediator between God and man. So prayers to Mary or a false version of God are not received. We are to pray in Jesus name.
"The researchers asked the members of three congregations -- St. Paul's Monastery in St. Paul; the Community of Teresian Carmelites in Worcester, MA; and Silent Unity, a Missouri [New Thought] prayer ministry near Kansas City -- to deliver the prayers, using the patients' first names and the first initials of their last names," the Times reported. It's of little wonder to the Bible-believing Christian why their prayers didn't work!
But even then, the Bible does not promise that God will grant a person's wishes. The Apostle Paul prayed three times for the Lord to take away what was tormenting him. But God replied, "My grace is sufficient for you, for my power is made perfect in your weakness" (2 Corinthians 12:7-10).
Paul said he would boast all the more gladly of his weaknesses, content with hardships insults, and persecutions, so the power of Christ would rest upon Him. Prayer works for God's glory before it's for our benefit. With thanksgiving to the Lord let your requests be made known to God, and the peace of Christ will come to you (Philippians 4:4-9) when we understand the text.