Compared with their thinner peers, overweight children may be more prone to developing depression and anxiety symptoms by the time they reach middle school, a new study suggests.

The study, which followed more than 1,200 U.S. children from age 2 to sixth grade, found those that those who were overweight tended to have more “internalizing” problems as they moved through elementary school - being somewhat more prone to becoming withdrawn, anxious or depressed.

They were not, however, at higher risk of conduct problems, like acting out at school.

The findings, published in the Journal of Pediatrics, suggest that poor body image or feeling ostracized by classmates may lead to internalizing symptoms in some children, according to the researchers.

However, parents should not worry that their children are at high risk of anxiety and depression simply because they carry some extra weight, stressed lead researcher Dr. Robert H. Bradley of the University of Arkansas at Little Rock.

“There is a relation between being overweight and having some depressive symptoms, but it’s a very modest relation, and many overweight children do not experience any anxiety or depression,” Bradley told Reuters Health.

He said that parents should be “watchful” for signs that their child is having problems - such as changes in sleep habits, withdrawal from their normal activities or unusual irritability - but should not become “overly anxious.”

Bradley and his colleagues based their findings on 1,254 children taking part in a government study of child development. Starting when their children were 2 years old, mothers periodically completed a standard questionnaire on child behavior; researchers also repeatedly assessed the children’s physical health and development as they grew older.

Starting in third grade, the researchers found, there was a clear relationship between children’s weight and subsequent internalizing symptoms.

The bottom line, according to Bradley, is parents, teachers and health providers should be aware of the signs that children are having such problems, and be ready to help them deal with any negative feelings connected to their weight.

SOURCE: Journal of Pediatrics, November 2008.