Eileen Paisley, widow of Lord Bannside, is one of the kind people who tell me they pray for me. I am always touched by this. I have a few illnesses, including cancer.
It is good to think people wish me well, and sincerely wishing somebody else the best is uplifting.
So her prayer is probably good for both of us. But can it cure leukaemia? Could it cure me?
Baroness Paisley, although she has prayed daily most of her life, makes no promises. She has a quotation from James' Gospel on the tip of her tongue. "Is any sick among you? Let him call for the elders of the church; and let them pray over him, anointing him with oil in the name of the Lord; And the prayer of faith shall save the sick, and the Lord shall raise him up; and if he have committed sins, they shall be forgiven him."
There are other biblical quotations, like Christ's last prayer, that suggest the purpose of prayer is to accept the will of God. On the cross, Christ prayed for acceptance and then forgiveness for the people who were crucifying him.
Baroness Paisley doesn't leave it at that, though. She readily agrees that life expectancy under modern medicine is higher than in earlier times, where only prayer was available.
Many claims on the power of prayer are personal. A former Miss Ireland, Rachelle Liggett, was prayed for when she had leukaemia at the age of 10. It must be a wonderful feeling to be supported like that and then to get a new lease of life. But the two are not necessarily related and, unfortunately, you are never entirely free of leukaemia, though it can be controlled and monitored. Many cancers are like that.
Rachelle has been symptom-free for years and looks the picture of health. She is lucky to have friends praying for her - you need support - but even luckier to live near one of the best cancer treatment centres anywhere.
There is independent research on prayer. The Cochrane Library, which monitors the efficacy of treatments, found that praying for something to happen doesn't have any demonstrable effect. It concluded: "Although some of the results of individual studies suggest a positive effect of intercessory prayer, the majority do not and the evidence does not support a recommendation either in favour or against the use of intercessory prayer."
Simon Singh, a researcher who examines alternative therapies like acupuncture and homoeopathy, found that patients who knew relatives were praying for them had a slightly better chance of recovery. He attributes that to the placebo effect which occurs when your body's defences are mobilised by something with no efficacy, like a sugar pill, after you are told it is a real drug.
In 2001, 799 coronary patients were divided into control groups and half prayed for, without any benefit. That was also the case in 2005 when 329 patients who were undergoing angiograms were prayed for by Buddhists, Hindus, Muslims and Jews as well as Christians.
In 2005 a $2.5m study reached the same conclusion, that prayer was ineffective, after studying 1,000 cardiac bypass treatments over several years.
What does this teach us? Disciplines like prayer and mindfulness meditation have been shown to work in nervous conditions and can help us deal with suffering. Being appreciated and thinking well of others makes us less stressed, and that can't be bad for anyone's wellbeing. But don't count on it to do the job of modern medicine.
In Zen Buddhism, which I practise, meditation is regarded as having little benefit if conducted with a "gaining idea". Perhaps prayer should be treated like that - less as a letter to Santa, more as something done for its own sake.
There is real harm in claiming more. What of those who are prayed for but still die? Were they unworthy or those praying for them not sincere enough?
These are cruel questions that can break hearts.