LONDON: Up to a million people in the UK have severe headaches caused by taking too many painkillers, doctors have said. They said some were trapped in a "vicious cycle" of taking pain relief, which then caused even more headaches. The warning came as part of the National Institute for Health and Clinical Excellence's (NICE) first guidelines for treating headaches. It is also recommending acupuncture in some circumstances. This can end up getting into a vicious cycle where your headache gets worse, so you take more painkillers, so your headache gets worse and this just becomes worse and worse and worse” There is no definitive UK data on the incidence of the condition, but studies in other countries suggest 1-2% of people are affected while the World Health Organization says figures closer to 5% have been reported.