Caffeine dependence is such a disappointment that usual coffee drinkers may get no real pick-me-up from their morning cup, according to a study by British scientists.

Bristol University researchers established that drinkers expand a tolerance to both the anxiety-producing and the stimulating effects of caffeine, meaning that it only brings them back to baseline levels of awareness, not above them.

Although regular consumers feel alerted by caffeine, particularly by their morning tea, coffee, or other caffeine-containing drink, confirmation suggests that this is in fact merely the reversal of the fatiguing effects of acute caffeine withdrawal, wrote the scientists, led by Peter Rogers of Bristol’s department of investigational psychology.

The team has asked 379 adults , half of them non/low caffeine consumers and the other half medium/high caffeine consumers  to give up caffeine for 16 hours, and then gave them either caffeine or a dummy pill acknowledged as a placebo.

Members rated their levels of anxiety, alertness and headache. The medium/high caffeine consumers who got the placebo reported a reduced in alertness and amplified headache, neither of which were reported by those who received caffeine.

But measurements showed that their post-caffeine levels of alertness were in fact no higher than the non/low consumers who received a placebo, suggesting caffeine only brings coffee drinkers  back up to “normal.”

The investigators also found that people who have a genetic tendency to anxiety do not tend to avoid coffee.

Actually, people in the study with a gene variant connected with anxiety tended to drink slightly larger amounts of coffee than those without it, Rogers wrote in a study in the Neuropsychopharmacology journal, published by Nature.

This suggests that a mild increase in anxiety and he said that may be a part of the agreeable buzz caused by caffeine.