(CBS/AP) The bad economy may be causing more than economic pain. A new study ties the nation's recent recession to a rise in child abuse, mostly in infants.

The five-year study - published online Monday in the journal Pediatrics - looked at child abuse in only 74 counties in four states, but it seems to confirm anecdotal reports from pediatricians, who say they've seen growing numbers of shaken baby syndrome and other forms of abusive head trauma.

So said study author Dr. Rachel P. Berger of Children's Hospital of Pittsburgh. She decided to study this type of injury after noticing an increase at her own hospital from late 2007 through June 2009. Her hospital averaged 30 cases a year during those recession years versus 17 yearly before 2007.

Though this abuse is still rare, the number of cases in the counties studied rose sharply, climbing from about 9 cases per 100,000 children in pre-recession years to almost 15 per 100,000 kids during the recession. That's a 65-percent increase.

Children studied were younger than 5, and most were infants. Most suffered brain damage and 69 died, though the death rate didn't rise during the recession.

Unemployment rates in the 74 counties rose during the study. The proportion of children on Medicaid in those counties also increased, from 77 percent before the recession to 83 percent. However, insurance and family employment information were not reported for the abused children in the study.

What might explain the rise in child abuse? Combine the stress of raising a young child with wage cuts or lost jobs and you get "a sort of toxic brew in terms of thinking about possible physical violence," said Mark Rank, a social welfare professor at Washington University in St. Louis. He said the study echoes sociological research linking violence with declines in economic well-being.

Along with U.S. Census data released last week indicating that a record 46 million Americans are poor, the study shows that "as poverty goes up and economic stagnation continues...there are really human costs involved," Rank said.

The counties studied included Pittsburgh and western Pennsylvania; central and southern Ohio; and a handful of counties in northern Kentucky and in the Seattle area. The researchers examined medical records and national labor statistics for 2004 through November 2007 and compared them with data from the recession.

Of the 422 children diagnosed with abusive head trauma during the study, roughly 65 cases occurred each year before the recession, versus about 108 yearly during the recession.

Federal government data suggest that the recession did not affect child abuse rates. But the study authors said those numbers are based on reports from child protective services, not medical diagnoses, and did not address brain injuries specifically.

The study doesn't prove the recession caused the abuse. Studying different regions and children from more middle-class families would help clarify if the recession really played a role, said Dr. Peter Sherman, director of the residency program in social pediatrics at Montefiore Medical Center in New York.

Sherman noted that most children studied were publicly insured even before the recession, suggesting that their families were already struggling financially.

Still, the recession affected many lower-income families, and Sherman said the study highlights "a very important issue."

He said pediatricians could help with prevention by asking families about difficulties paying for food or shelter and referring those in need to social service agencies. Just asking parents about stress and acknowledging their struggles can sometimes help, he said.

Most parents who abuse young children aren't "ill-intentioned," he said. "Most of it is kind of just snapping...maybe being sleep-deprived and just losing it. It's something that can happen to anyone."