Central pain stems from damage to the central nervous system -- the brain, brain stem and spinal cord. It differs from ongoing pain from bone or muscle conditions such as arthritis, or peripheral nerve pain like diabetic neuropathy.
Researcher Forest Tennant, MD, of Intractable Pain Management, presented the findings at the PAINWeek 2015 conference.
For the study, 45 people with chronic pain attending a treatment clinic completed a 16-item questionnaire. The questions asked whether the person had trouble with concentration, attention, distractibility, impulsivity, reading and retention, coordination, temper, and short-term memory.
A positive answer to five or more questions was considered to indicate ADHD.
Results showed that 37.8% of the people met these criteria for the disorder.
Most people with centralized pain have an overactive autonomic nervous system, the part of the nervous system responsible for functions like breathing. This contributes to the ADHD (which is sometimes called ADD, or attention deficit disorder).
The finding might help explain why some people with pain have trouble with activities in their daily lives, Tennant says.
"For years, I've seen the same kind of ADD in these patients that you see in children -- they can't remember half the time, they can't concentrate," he says. "It's amazing how many of these patients actually quit reading or doing things, but they won't tell you."
But once they start taking medication for ADHD, "their pain gets better and they can remember and concentrate."
Tennant stressed that the findings [do not apply to] those with arthritis or neuropathic pain.
Jack LeFrock, MD, a pain specialist at Above and Beyond Pain Management and Laser Center, says Tennant's finding "makes sense."
"I agree with him; I think he's right on," he says.
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.