If she were right there would be about 10 million more Americans addicted
to meth. What she needs is information about ADHD and how
to help a child with it. But
to answer your question, the book, "The ADD/ ADHD Answer book," by Susan Ashley ( I highly recommend you both buy it), says "those who were not treated with medication were over three times more likely to develop a substance abuse disorder" (p. 225).