>Liza May:
>...Astrid Nehlig, Ph.D., of the French National Health and
>Medical Research Institute ...(snip)... caffeine appears to
>act differently from amphetamines, cocaine, morphine or
>nicotine, Nehlig says. These drugs are known to trigger
>functional activity in the shell of the nucleus accumbens,
>the part of the brain responsible for addiction even at low
>doses, she says.

I don't know anything about nuclei accumbens, but speaking
strictly for me, up until very recently I drank about 12 oz. of
brewed coffee, what they'd probably consider 2 cups, a day.
Any time I didn't get it I'd get one heck of a nasty headache
for about 12-16 hours or so, starting around 30 hours after
my last "fix".  To me, that's an addiction.  Even if the
withdrawals aren't as severe as with these other drugs.

Cheers,
Martha