Increased breast-feeding during the first months of life appears to raise a child's verbal IQ, according to a study of nearly 14,000 children released Monday.

The study in Archives of General Psychiatry found that 6-year-olds whose mothers were part of a program that encouraged them to breast-feed had a verbal IQ that was 7.5 points higher than children in a control group.

The researchers said their findings suggested that the longer an infant is fed breast milk exclusively, the greater the IQ improvement.

The results echo smaller previous studies that found children and adults who were breast-fed tend to have higher IQs than those who were not.

Lead author Dr. Michael Kramer, a professor of pediatrics at McGill University in Montreal, said the IQ improvements were modest and might not be noticeable on an individual basis. But he added that the increase could have a significant effect on society as a whole.

The latest study tracked breast-fed infants born between June 1996 and December 1997 in Belarus.