Originally Posted by BlackCrayon

Between 1990 and 1995, use of methylphenidate more than doubled, according to a 1996 study at Johns Hopkins University. By mid-1995, it found, nearly 3 percent of American children and youths, or about 2.5 million, were taking it. And that number appears to have kept rising, so that by now, it may have hit 3.75 million, according to a rough estimate by Dr. Lawrence Diller, author of "Running on Ritalin" (Bantam, 1998).

From what I've read it seems the majority of kids who have shot up schools were on some kind of SSRI's.