The study is in the May 21 issue of the Journal.
It looked at results of limiting resident doctors to an 80-hour work week, 30-hour shifts and lighter workloads. The study concluded the limits can have drawbacks.
The study's author says the number of medical errors have not decreased since the guidelines went into effect beginning in 2003.
But residents say the rules are widely ignored by teaching hospitals.
The Institute of Medicine (IOM) has called on the country's 1,200 teaching hospital to follow the guidelines, increase supervision and adopt even shorter shifts. The IOM is recommending shifts no longer than 16 hours, or 30 hours with five-hour naps.
The study's author said adopting the IOM recommendations would cost each major teaching hospital $3.2 million per year.