London, Oct 31 Aside from Lord Voldemort, the Forbidden Forest and the Dementors, young fans of the wildly popular Harry Potter books apparently have one more thing to worry about: “Hogwarts headaches”.

Howard J. Bennett, a paediatrician in Washington, D.C., was alerted to the peril when three patients, ages 8 to 10, came to him in June complaining they were suffering from a headache for the past two or three days.

“In each case, the headache was dull and the pain fluctuated throughout the day,” Bennett wrote in a letter published in today’s issue of The New England Journal of Medicine.

One of the children also complained of neck and wrist pain, but none had a fever or any other symptoms that would suggest they were suffering from something serious, like an infection or neurological problem, he said.

“On further questioning, it was determined that each child had spent many hours reading J.K. Rowling’s latest book in the Harry Potter series,” Bennett wrote in the letter, which journal editors titled Hogwarts Headaches — Misery for Muggles.

Hogwarts is the name of the school for witches and wizards that the bespectacled Potter attends in Rowling’s books. Muggles is the wizard name for regular humans. “The presumed diagnosis for each child was a tension headache brought on by the effort required to plow through an 870-page book. The obvious cure for this malady — that is, taking a break from reading — was rejected by two of the patients, who preferred acetaminophen instead,” Bennett wrote, referring to the pain-killer sold as Tylenol and other brand names.

For one of Bennett’s patients, Lillie Lainoff, 8, the headaches started the night that Harry Potter and the Order of the Phoenix, the fifth installment in the series, arrived in book stores. Lainoff and her mother rushed out to buy a copy as soon as it became available, and the Potter fan spent the next several hours devouring the young wizard’s latest adventures.

“I would read for a time and I would feel a pain in my head and it would keep going and going and it would keep getting worse,” Lainoff said.

At first Lainoff’s mother was uncertain if the headaches were caused by the heft of the book or the suspense of waiting to find out which character was going to die. “What I was trying to figure out was whether it was content or the poundage,” said Lainoff’s mother, Kathryn Kincaide. Bennett told her that her daughter’s headache was in all likelihood brought on by the size of the book, and suggested Lainoff take 20-minute breaks periodically to keep the headaches at bay, just as exclaiming “expecto patronum” protects Potter and his friends against the evil Dementors. Reluctantly, Lainoff complied.

In all three cases, the headaches went away one or two days after the patients finished plowing through the book, he said. Bennett, who had not seen similar cases “with any of the previous Harry Potter tomes,” noted each of Rowling’s books has been bigger than the last. “If this escalation continues as Rowling concludes the saga, there may be an epidemic of Hogwarts headaches in years to come,” he wrote.

Amy Spengler, a spokeswoman for Rowling’s publisher, Scholastic Trade Books, said neither the company nor the author had any comment on Bennett’s letter.

Bennett stressed in a telephone interview that he was a fan of Rowling’s books and in no way meant to criticise the author or her series.

“The last thing I want is for anyone to think this is a criticism of J.K. Rowling and what she’s done — she’s got kids reading,” Bennett said. “It’s just valuable for other doctors to know that this might be one possibility when kids come in suffering from a headache.”