David Wright wrote:

Thanks for your comment Jeff but I suspect there are still some out
there who are not aware of the carcinogenicity of Ritalin.

Like you, for example. I could only find two studies on the subject,
both in rats or mice. The conclusion was that there was little
evidence of carcinogenicity from methylphenidate,and in some cases it
actually seemed to *reduce* the instance of tumors.

"a little evidence of carcinogenicity" is enough for me.