Children who suffer from ADHD symptoms usually get much better after starting the treatment with stimulant drugs and in these terms, the drugs are beneficial. However, a major U.S. study done to evaluate the effects on stimulant drug Ritalin showed that kids who had been taking the drug are about an inch shorter and 4.4 pounds lighter than their peers three years after the treatment.

Scientists found that ADHD medications do have growth-suppression effects.

The study is not definite yet and there are still many questions to be answered, one of them being whether the children would grow to normal size eventually and if the drug would affect their ultimate height.

Ten years ago, a National Institutes of Health panel reported that the stimulant drugs carried no long-term growth risk and never warned parents about this possible side effect.

Another option was that ADHD itself stunted kids' growth. However, the study results showed this was not the case since children with ADHD who underwent no medical treatment were bigger than the children who took the drugs as well as the healthy children.

Children who starting taking Ritalin, immediate-release, three times a day, every day of the year, at the beginning of the study grew more slowly than normal kids as the study went on. The results on the ultimate height won’t be available for the next few years.

Three years after the beginning of the study, Ritalin effects started to wear off. After this time, medical treatment effects started wearing off while the pure behavioral treatment was still effective.

The study focused on the immediate-release Ritalin and did not test the sustained-release stimulants that are now used as the standard treatment for ADHD.

Health experts warn that parents should be aware of the medications affecting the brain and make growth monitoring the standard procedure.