The spell cast by the latest Harry Potter book may haveanunintended side effect. A Washington doctor warned that he hasseenthree children complain of headaches caused by the physicalstressof relentlessly plowing through theepic870－pageadventure.Dr.Howard Bennett of George WashingtonUniversity Medical Center wrotein a letter to this week＇s NewEngland Journal of Medicine that thethree children, ages8to10,experienced a dull headache for two orthree days. Each hadspent many hours reading″Harry Potter andthesgroupsof thePhoenix.″

　　After ruling out other potential causes, Bennett told hispatientsto give their eyes a rest. But the spell cast by the bookwasclearly too powerful.″The obvious cure for thismalady———thatis,taking a break from reading———was rejected by twoof the patients,″Bennett said, adding that the children tookacetaminophen instead.In each case, the headache went away onlyafter the patient turnedthe final page.