WHAT YOU CONSUME can have an effect on your stress hormone level, for better or worse. Obvious examples are caffeine and nicotine. Even in moderate doses, either of these can double the amount of adrenaline in your bloodstream.
The stress of something like an exam produces increased cortisol levels (cortisol is a primary stress hormone). Combined with coffee, however, the cortisol levels rise even more.
Coffee all by itself raises your cortisol level, increases your feelings of stress and anxiety, raises your blood pressure — and all this even if you are otherwise relaxed, and even for people who drink it regularly. It also makes hypertension medications less effective.
In a study, a fairly big dose of caffeine was found to mimic the symptoms of anxiety disorders. Withdrawal from caffeine does too.
Some people react more strongly to caffeine than other people. Studies have found that people with panic disorder (one of the five anxiety disorders) have a more robust reaction than "normal" people to equal amounts of caffeine. They experienced more fear, heart palpitations, nervousness, restlessness, etc. Caffeine can increase these kinds of symptoms in anybody. But for some people, it is more dramatic.
You may not have panic attacks, but it is possible and worth considering the possibility that your system might be more sensitive and react more strongly to caffeine than the average person. In one experiment, five out of six people were cured of their panic attacks by doing nothing more than giving up coffee. Caffeine blocks the action of a brain chemical called adenosine, a naturally-occurring sedative.
In one study, people with panic disorder could reliably produce panic attacks with four or five cups of coffee. Coffee can produce panic attacks in even normal people, but it usually takes more coffee than that.
In another study, people were tested for anxiety, depression, and caffeine consumption. There was a direct correlation between the level of anxiety and caffeine consumption — but only in those with panic disorder.
This doesn't mean if you don't have panic disorder, coffee is fine for you. Caffeine has a significant effect on everyone. It is merely more pronounced in some people.
In yet another study, panic disorder patients and normal people were given equal doses of caffeine (ten milligrams per kilogram of body weight). Then they were all tested for anxiety symptoms: fear, nausea, nervousness, pounding heart, tremors, and restlessness. The caffeine had caused a significantly greater intensity of these symptoms in the people with panic disorder than in the normal people — but even normal people suffered many of these symptoms.
Given all this, if you'd like to reduce your stress, I suggest an experiment. Quit ingesting caffeine for two weeks. It takes about three days for withdrawal symptoms to completely subside (headaches, feelings of lethargy, etc.). After that, pay close attention to the general feeling-tone of your day-to-day experience — your sense of relative ease, comfort, annoyance, distress, alarm, contentment, etc.
Then start drinking coffee again. The first day it'll feel great (as long as nothing too stressful happens). The next day and the next, pay attention to the general feeling-tone of your experience. If you're like me, you'll notice a general but subtle feeling of alarm. And you'll notice circumstances feel more distressing.
Then ask yourself what coffee does for you. You get a great feeling of relief in the morning with your first cup. After going all night without caffeine, your body is in the beginning of withdrawal, so it feels good to get a dose again. That's always the moment coffee advertisers display — that first cup in the morning.
Also the general feeling of sharpness and alertness is a plus.
But there are plenty of downsides too. I'll admit, coffee is a hard thing to give up, even if you know you'd be better off. But the worst is over in a few days and then you'll notice some positive effects on your mood and general feeling of well-being.
Weigh the pluses against the minuses and I think you'll find coffee comes out on the short end of the stir stick almost every time.