CHICAGO — Children and teens with attention-deficit hyperactivity disorder fared no better on St. John’s wort than they did on dummy pills in a government study, another setback for herbal supplements.

St. John’s wort, pine bark extract and blue-green algae are among commonly used herbal treatments for children with ADHD. They appeal to parents who want to avoid stimulants like Ritalin and other drugs used to help children control their behavior.