I told her not to do it. She soon had many girls in her room wanting to read about drugs, so we realized there was a need for an accurate and unbiased source of information, and thus we wrote Buzzed. Probably the most damaging and abused drugs are alcohol and tobacco. We don't all think of them as drugs, but far and away most health problems related to substance abuse come from these. Beyond that, it's almost certainly marijuana and emerging ecstasy, in adolescents.
Addiction is a very special process.
In fact if you miss your caffeine once you've become tolerant, you become unhappy and have a headache. What your body has experienced is tolerance and then withdrawal from caffeine, and then unpleasant effects. But that is not addiction. Addiction is defined as the use of a substance or behavior despite negative consequences and a compulsive fashion. Drugs that are addictive are those that interact with the brain's reward system.