ROCKVILLE, Md., June 30 - Federal health officials said Thursday that they were looking into a suggestion by a small Texas study that Ritalin and other stimulant drugs given to children might increase their risk of cancer later in life. A team of experts from the Food and Drug Administration, the National Institutes of Health and the Environmental Protection Agency went to Texas on May 23 to examine the methods used by the researchers, who found damage to the chromosomes of 12 children who took Ritalin for three months. Ritalin, which entered the market in 1955, has been used for...