Anti-psychotic drugs commonly used to treat Alzheimer's disease may double a patient's chance of dying within a few years, suggests a new study that adds to concerns already known about such medications. "For the vast majority of Alzheimer's patients, taking these drugs is probably not a worthwhile risk," said Clive Ballard, the paper's lead author, of the Wolfson Centre for Age-Related Diseases at King's College London. The research was published Friday in the medical journal, Lancet Neurology. Ballard and colleagues followed 165 patients aged 67 to 100 years with moderate to severe Alzheimer's disease from 2001 to 2004 in Britain. Half continued taking their anti-psychotic drugs, which included Risperdal, Thorazine and Stelazine. The other half got placebos.