Can coffee still be more beneficial than harmful if you suffer withdrawal effects? I have some co-workers who get headaches if they try to have a morning without coffee.
That's a known thing. Drinking coffee blocks adenosine receptors (which affect tiredness). In result, they increase in number to compensate that. So if you stop drinking coffee, the increased number of receptors causes more intense feeling of tiredness. If you stop drinking coffee for a long time, the number of receptors adjusts back down.