There are a few studies that come to mind. One had to do with high blood preassure. There was no preferance for Christians over other religions, but in general, they more someone attended church, the more they read their Bible and prayed, the lower their blood preasure was.
Another study I remember was a five year study on people who are giving people or who do things to help others. It could be something as small as just picking up a news paper for a neighbor. The study found the health of giving, helping people is better and they live longer. The women really tried hard to make adjustments for people who are to sick to begin with to do anything to help others. But the results showed that selfish people have more health problems and they die sooner than people who do what they can to help others.
In general the studies have found that calling yourself a christian does not seem to make any difference. But doing things that would be considered christian, does seem to make a difference.