Regardless of what you want to believe doctors believe that it helps: http://www.Webmd.Com/balance/features/can-prayer-heal or
http://www.Healthsearches.Org/Categories_of_Q&A/Integrative_&_Alternative_Medicine/1305.Php these are not Christian sites but they do show that prayers help your body heal. We may not understand how this works or why, for me I trust God and believe he helps but even those who do not believe get help.
Prayer has no direct effect on the real world. If it did it would be reflected in a number of sectors from death rates to wealth. Prayers may be beneficial in the way that they comfort some people but on the whole prayers are in fact dangerous. I myself know people who have denied themselves medical treatment on the basis that the power of prayer will be sufficiant to heal them. I dont doubt that plenty of people have died or otherwise been harmed because they put their lives in the hands of prayer and fatih.
People who beleive in the power of prayer also use a strange form of logic. If something seemingly goes their way it is seen as a sign that God has answered their prayers but if things go the other way God must just not be listening or working in mysterious ways. I mean how many times are prayers going to go unanswered or appear to happen in a way that implied no special attention from a deity before people realise that prayer is a waste of time.