Is 600,000 an epidemic?

In Frontline: The Meth Epidemic, Glenn Garvin writes,

The U.S. government's own National Survey on Drug Use and Health says that from 2002 to 2004, the last year for which data is available, meth use did not increase at all. Nada, nothing, zero, zip.

...

Oh, and those 1.5 million meth addicts Frontline mentions -- well, don't waste your time trying to find them. When you actually look up the National Survey on Drug Use statistics, that's the number of Americans who have ever, at any time in their lives, tried meth. The closest thing to a figure for addicts is the survey's number of people who used meth in the past month, which is about 600,000. If that's an epidemic, then so is the Home Shopping Channel.