The report found that in places where integration had increased by at least 5 percent, the cost of outpatient services was an average of $75 higher per month for each insured patient. The study did not find evidence that the cost of inpatient services rose, however.  

While integration no doubt promotes a number of efficiencies that should lower costs, the study authors posited that more consolidation has empowered hospitals in their negotiations with insurers.  

"Financial integration between physicians and hospitals may help health care provider organizations meet the challenges of new payment models but also may enhance the bargaining power of provider organizations, leading to higher prices and spending in commercial health care markets," they wrote.  

Responding to the report in the Wall Street Journal, the American Hospital Association dismissed the findings, saying that the rate of hospital price growth was at an all-time low. It touted low price growth to new forms of payment.  

Gerard Anderson, director of the Johns Hopkins Center for Hospital Finance and Management, suggested that the higher costs for hospitals that have bought physician practices may simply be their attempt to recoup the money they spent buying the practice.  

"It was a bad financial investment before and it seems like we're doing it again," he said.