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COFFEE addicts may be unusually sensitive to pain and prone to panic
disorders. A team led by Björn Johansson of the Karolinska Institute in
Sweden looked at mice that had had the gene coding for an adenosine receptor in
their brains disabled. A high dose of caffeine has the same effect in people.
The mice seemed healthy, with normal growth and heart rates, but tests showed
they were unusually anxious and sensitive to pain (Proceedings of the
National Academy of Sciences, vol 98, p 9407). People who drink up to
around six coffees a day should be all right, since this amount of caffeine
blocks only half their adenosine receptors. But higher doses might cause similar
symptoms.