Back pain, migraine and other types of chronic pain without a known physical cause - and therefore little prospect for relief - were associated with an increased risk of suicide in a new study of US veterans. But the researchers, who analysed data on about five million patients in the US Department of Veterans Affairs Healthcare System, found no link between suicide and arthritis, neuropathies or non-migraine headaches.
Dr Mark Ilgen, the study's lead author, said the findings jibe with what he and his colleagues expected to see based on their own experiences and past research.
"I think we had the expectation that certain conditions - such as migraine and back pain - would be especially problematic when it came to suicide risk," Ilgen said, from the VA Ann Arbor Healthcare System in Michigan.
That's because of differences in the origins, intensity and treatability of various chronic pain conditions, he said. For example, there are treatments available for chronic pain brought on by arthritis, which is caused by joint inflammation. But fewer options are available for psychogenic pain - a diagnosis that literally means "originating in the mind" with no known physical cause.
"My sense is that the level of pain that they're seeing in arthritis is not as severe and debilitating as what people are seeing in the back pain group and psychogenic pain," said Dr David Marks, a psychiatrist and pain medicine physician at the Duke University Medical Center in Durham, North Carolina.
Past research has focused mainly on links between chronic pain and so-called suicidal behaviours, such as suicidal thoughts and attempts, according to the researchers.
Benefit to doctors
For their study, Ilgen and his colleagues write in JAMA Psychiatry that they wanted to look at possible links between specific pain conditions and completed suicides.
They used data on 4 863 036 patients receiving care in the VA health system between October 2004 and September 2005 and then looked to see how many with a chronic pain condition killed themselves between October 2005 and September 2008.
Over two million people were diagnosed with arthritis and about 1.1 million people were diagnosed with back pain, which made those conditions the most common. Only about 18 000 people had psychogenic pain, which made it the least common condition. About 5 000 people committed suicide over the next three years.
After taking into account the patients' ages, sex and other physical and psychiatric conditions, the researchers found that back pain, migraine and psychogenic pain were the only chronic pain conditions linked to suicide. Back pain was linked to a 13% increased risk of committing suicide, compared to people without chronic pain. Migraines were linked to a 34% higher suicide risk and psychogenic pain was linked to a 58% increase in risk. As far as how important these conditions are as risk factors for suicide, Ilgen said they "wouldn't be at the top of the list, but they still matter."
The findings also cannot prove these conditions are what caused the patients to commit suicide. And Ilgen noted that the findings may not apply outside this specific population.
"I think the results probably generalise reasonably well to middle-aged males in the general population. If you want to apply the results to women, that's a little bit more challenging," he said. Marks, who was not involved in the new research, said that despite the fact that only a minority of the people with chronic pain actually killed themselves, the study benefits doctors.
"It points out to pain providers that pain is a significant risk factor for
suicide that needs to be screened for and taken into account," he said.