Do hospitals, like resort hotels, have an offseason? If they do, the month of July might be it. The so-called July effect has long been suspected. It's based on the fact that new U.S. doctors start their residencies (in-hospital training) each July 1 in thousands of "teaching hospitals" nationwide. But until recently, the idea that hospitals are especially dangerous in July was little studied. Now, some study results are in. And if you are hospital-bound in the next few weeks, you can find cause for both reassurance and worry.