Here is some evidence against using these drugs for recreational/non-ADHD use:
http://www.cesar.umd.edu/cesar/drugs/ritalin.asp
http://www.biopsychiatry.com/methylphenidate/ritalin.html
http://www.cesar.umd.edu/cesar/drugs/ritalin.asp
http://www.biopsychiatry.com/methylphenidate/ritalin.html
So, a developing child a doctor decides has ADD will experience these, and probably worse if it impacts development.