(Portland, OR)  --  Children with ADHD can have their symptoms improved by taking vitamins and minerals.  A study by the Oregon Health & Science University confirmed results in a previous study in New Zealand.  54-percent of children who were given supplemental vitamins and minerals showed improvement in their symptoms compared to 18-percent in a placebo group.  The study involved 135 children in Portland, Columbus, Ohio; and Alberta, Canada.  The results were published in the Journal of the American Academy of Child and Adolescent Psychiatry.