That article raises a good point, too. Caffeine withdrawal - which is definitely a thing I've experienced. It makes a strong point for therefore considering it a "drug".

Damn. I thought I was safe from drugs, having gone off alcohol completely years ago. Sigh. :)

"Caffeine Withdrawal Leads To Negative Side Effects Such As Headaches

We should remember that caffeine is a drug, and like many drugs, there can actually be a withdrawal period when we give it up."