Over the years, there has been much concern over the possibility that Methylphenidate (brand name: Ritalin) might cause growth suppression in children with ADHD who are treated with the medication. A number of studies have been done, with most supporting the idea that if there is a slowing of growth, the side effect disappears within a few years, with the child reaching his normal potential height.

Yet, in the August 2007 issue of the Journal of the American Academy of Child and Adolescent Psychiatry, lead researcher James Swanson, Ph.D., director of the Child Development Center at the University of California, Irvine reported that after three years on the ADHD drug Ritalin, children were about an inch shorter and 4.4 pounds lighter than their peers. The children studied (in 1999) were ages 7 to 9 at the time and were followed for three years; however the results of the 10 year follow up- when the children reach adult height- won't be available for another two years. Thus, it is unknown yet whether the growth loss is permanent or not.

Unlike earlier studies which showed that children had growth spurts to make up for the slow down earlier on, this study did not support that. In addition, it was thought that having ADHD in and of itself stunted kids' growth, but this study found that kids with ADHD who do not take stimulant medications are actually much larger than kids without ADHD and that they- those with untreated ADHD- seem to grow faster than those taking stimulants.

According to Dr. Swanson, children who had been taking stimulants before this particular study, were smaller than those who had not yet started stimulant treatment. Those who first began treatment at the start of the study were of normal size and weight, but compared to others, their growth rate slowed down as the study went on.

After three years of taking immediate release Ritalin three times a day, the growth suppression seemed to slow down, as did the effect of the medication, interestingly enough.

It should be noted that in this study, only the immediate release form of Ritalin was used.

In 2006, Omar Khwaia, M.D., Ph.D, a neurologist at Children's Hospital in Boston, analyzed studies of various ADHD medications and found evidence of growth suppression. His findings were similar to Dr. Swanson's.

Again, since the studies were short term, it is still unknown whether the children regain their loss in height while taking short acting Ritalin.

Yet, a newer study, reported by Robert Findling, M.D, at the May 8, 2008 poster session at the 161st Annual Meeting of the American Psychiatric Associations (APA) revealed a very different finding. Dr. Findling, Director, Division of Adolescent and Child Psychiatry, University Hospitals Case Medical Center, and Professor of Psychiatry, Case Western Reserve University, Cleveland, Ohio found that the children in his study demonstrated normal growth in height and weight but not in BMI. Body mass index (BMI) is a measure of body fat based on height and weight.