Antidepressants commonly used to treat chronic pain lack evidence as to whether or not they work, researchers have said, declaring the situation a global public health concern.
Chronic pain, typically defined as pain lasting three months or more, is a widespread problem affecting up to one in three people, with conditions ranging from osteoarthritis to fibromyalgia.
While exercise is often recommended, this is difficult for some patients, while there are concerns that opioids and other painkillers such as aspirin and paracetamol could do more harm than good.
Increasing numbers of patients are prescribed antidepressants to treat their pain, with hundreds of thousands in the UK estimated to be taking amitriptyline. Antidepressants affect chemicals known as neurotransmitters, which is how they are thought to relieve pain.