Caffeine a Drug?

In lectures on Advanced Biblical Counseling at the Master's Seminary, speaking about drug and alcohol addiction, Dr. John D. Street was asked about caffeine addiction. He responded with the following, which I think is insightful and properly challenging:

When I have to have it in order to function normally, then it becomes an issue. 'I HAVE TO have it.' We may not steal, cheat, or murder in order to get our caffeine, but if I have to have it (otherwise I'm going to be irritable, I'm going to bite your head off, I'm going to have headaches all day long, and I'm not going to interact well with people), now I'm resorting to sinful responses to people without that chemical. Then that particular chemical has a control in my body and in my thinking–a mastery in my body and in my thinking–that it shouldn't have.