Vast sums are wasted on treatments for back pain that make it worse

FOR SOME people it starts with an injury: a skiing accident or a car crash. For others it starts with something seemingly innocuous, like picking up a pair of socks from the floor. But for most, back pain is as mysterious as it is excruciating. Some 85% of chronic sufferers have what doctors call “non-specific” back pain, meaning it has no clear physical cause.

In most countries, whether rich or poor, back pain is the leading cause of disability, measured by the number of years lived in poor health (see Briefing). It often strikes people in middle age and keeps them wincing, on and off, for the rest of their lives. Many lose their jobs, either because they feel physically unable to work or because they become depressed. Back pain is the main reason why Europeans drop out of work and a big reason why Americans get hooked on opioids.