At least 46,600 children along the Gulf Coast are still struggling with mental health problems and other serious aftereffects of 2005 hurricanes, according to a new study by the Mailman School of Public Health at Columbia University and the Children’s Health Fund.

Many of these children are performing poorly in school and have limited access to medical care, according to the study, which combines government statistics with data collected by a group of researchers that has been closely following about 1,250 families displaced by the storm.

The children most at risk are those who have returned to their home states of Louisiana and Mississippi but lack stable living situations, the study says.

They are children like Nicole D. Riley’s daughter Isis, who is about to turn 4. Her family left New Orleans the day before Hurricane Katrina and moved five times over a short period before ending up in the large government-operated trailer park in Baker, La. All those moves “really didn’t sit well with her,” Ms. Riley said of her daughter. “When we got out here to the park, she was out of control, out of hand. She was not like that before the storm.”