Researchers at the Muhlenberg College in Pennsylvania surveyed 4,000 Potter fans for this study and found at least 10 percent of them to be hampered by symptoms akin to drug addiction. Some of these symptoms included sleeplessness and loss of appetite.

"Some readers can become so engaged in the series and the ancillary world that grew out of it that they report behaviors -- that truly fit definitions of addiction or dependence," said lead researcher Professor Jeffrey Rudski.

Some 20 percent of those surveyed in the study were on the verge of addiction, the researchers said, adding that 10 percent of them spent at least four hours per day with Harry Potter. These people had very little physical activity and got irritated very easily.

Harry Potter is a mythical boy wizard, whose exploits with his friends Ron Weasley and Hermione Granger have been chronicled by J.K Rowling. The final book of the seven book series was called Harry Potter and the Deathly Hallows and was released least year.