(NaturalNews) Children taking stimulants as a treatment for attention-deficit hyperactivity disorder (ADHD) are 20 percent more likely to visit a doctor with heart-related symptoms, according to a new study conducted by researchers at the University of Florida and published in the journalResearchers examined the records on 55,000 children between the ages of 3 and 20 who had undergone treatment for ADHD using central nervous system stimulants between 1994 and 2004. Their health profiles were compared with those of nearly two million other children in the Florida Medicaid database, making the current study the largest ever on the safety of ADHD drugs.Children taking stimulants were 20 percent more likely than other children to visit the emergency room or doctor's office with heart-related symptoms like a racing heartbeat.The researchers did not find any difference in the rates of hospitalization or death from heart-related causes among children taking stimulants. But other drugs in the methamphetamine class, to which ADHD drugs Ritalin and Adderall belong, have indeed been known to cause serious cardiac side effects.In 2006, the Drug Safety and Risk Management Advisory Committee of the FDA recommended adding a black-box warning to ADHD drugs about cardiovascular risks. This is the strongest warning that the FDA can place on a drug before pulling it from the market. But the FDA's Pediatric Advisory Committee urged against such a warning, saying that the cardiac side effects were not serious and could be easily managed by changing the size or timing of drug doses.The University of Florida researchers noted that more than 25 percent of people who used stimulants in the study were also found to be taking antidepressants or antipsychotics, which have also been shown to affect the cardiovascular system. They said that more research is needed into circumstances that might predispose children to heart trouble, and to determine if ADHD medications can exacerbate those problems.