If OP's still confused over this and is serious about this, do you live in the United States? If so, you've probably seen commercials for anti-depressants on TV at some point or another. And in those commercials, you've probably heard lines like "please contact a doctor immediately if you have suicidal ideation, etc, etc". And that line's there because for some people certain anti-depressants indeed end up having the opposite of the intended effect and end up making the problems worse. And that's because of just how complicated the body is and different things affect people differently and that unfortunately there's no such thing as panaceas and while there are broad trends and norms with medicine, the key word there is trends and a lot ultimately comes down to the individual.
Same deal here. Some people caffeine works really well for, other people don't really feel much of anything. Bodies are complicated, everyone is different, etc. This isn't a case of winning an argument and one person telling the truth and another lying, or anything like that, but just a case where everyone's telling the truth and it affects different people differently and while their might be general trends with caffeine that doesn't preclude individual differences that deviate from that, just like with say anti-depressants and how the general trend is they do indeed help many people and while such severe side-effects aren't the norm by any stretch and thus why they're sold in the first place, it can also be true for others specific ones make the problems worse due to those same kind of factors and individual differences. That's all.