Anticipation of pain can be worse than pain itself - health - 22 November 2013 - New Scientist

"The only thing we have to fear is fear itself," said Franklin D. Roosevelt. He might have been onto something: research suggests that the anticipation of pain is actually worse than the pain itself. In other words, people are happy to endure a bit more pain, if it means they spend less time waiting for it.

Classical theories of decision-making suppose that people bring rewards forward and postpone punishments, because we give far-off events less weight. This is called "temporal discounting". But this theory seems to go out the window when it comes to pain.

One explanation for this is that the anticipation of pain is itself unpleasant, a phenomenon that researchers have appropriately termed "dread".

To investigate how dread varies with time, Giles Story at University College London, and his colleagues, hooked up 33 volunteers to a device that gave them mild electric shocks. The researchers also presented people with a series of choices between more or less mildly painful shocks, sooner or later.

During every "episode" there was a minimum of two shocks, which could rise to a maximum of 14, but before they were given them, people had to make a choice such as nine extra shocks now or six extra shocks five episodes from now. The number of shocks they received each time was determined by these past choices.

No pain, no gain

Although a few people always chose to experience the minimum pain, 70 per cent of the time, on average, participants chose to receive the extra shocks sooner rather than a smaller number later. By varying the number of shocks and when they occurred, the team was able to figure out that the dread of pain increased exponentially as pain approached in time. Similar results occurred in a test using hypothetical dental appointments.

"This study demonstrates that the fear of anticipation is so strong it can reverse the usual pattern of time discounting," says George Loewenstein, a professor of economics and psychology at Carnegie-Mellon University in Pittsburgh, Pennsylvania. "It's probably not an exaggeration to say that as much, or more, of the pains of life come from anticipation and memory than from actual experience."

The study could well have implications for medicine and health policy, because an understanding of how people judge pain is important for presenting them with options about potentially painful treatments.

"You should avoid emphasising waiting times," says Story. "And if you can make something seem unavoidable, people may be more likely to confront it to minimise dread."

Story hopes that this kind of psychological study will aid the development of diagnostic tools. "Looking at these kinds of preferences might help predict whether people will make healthy or unhealthy choices," he says.

Journal reference: PLoS Computational Biology, DOI: 10.1371/journal.pcbi.1003335

http://www.newscientist.com/article/dn24642-anticipation-of-pain-can-be-worse-than-pain-itself.html#.UpHnNpHf4-t

Pain and Relief Signals Muted in Fibromyalgia - MedPage Today

Patients with fibromyalgia showed less activation in brain responses to pain-related "punishment and reward" anticipatory signaling on functional MRI than healthy controls, a small study showed.

Compared with patients with fibromyalgia, controls had significant increases in signaling in the right ventral tegmental area (VTA) while anticipating pain (P<0.01) and a trend for greater signal activation while actually experiencing pain (P=0.059), according to Marco L. Loggia, PhD, of Harvard Medical School, and colleagues.

Controls also had greater decreases in VTA signaling when anticipating relief from pain (P<0.05), suggesting that patients with fibromyalgia experienced blunting of these anticipatory pain and relief responses, the researchers reported online in Arthritis & Rheumatism.

It's becoming widely recognized that fibromyalgia is characterized by heightened sensitivity to pain, most likely because of abnormal central processing of painful stimuli.

However, little is known about how anticipation of pain and relief may contribute to the affective and cognitive aspects of the experience of pain.

"Expectancy and pain-relevant anxiety, in particular, have been shown to shape subsequent perceptual states. Relief from pain, on the other hand, is a positive hedonic experience intrinsically linked to pain," Loggia and colleagues explained.

To explore whether these components of pain might be altered in chronic pain states such as fibromyalgia, the researchers performed functional MRI studies in 31 patients with fibromyalgia and 14 controls, primarily focusing on the VTA and the nucleus accumbens.

These are areas of the brain involved in reward and punishment processing that also have been linked with fibromyalgia on positron emission tomography.

The pain stimulus for each participant was provided by an inflated pressure cuff on the lower leg, which initially was inflated to 60 mm Hg. Pressure then was increased until participants reported a pain rating of at least 50 out of 100.

Color-coded visual cues were used to induce anticipation of pain and relief. Before inflation of the cuff, a black cross was projected into the participant's visual field, changing to green to signal that the painful stimulus was about to begin. With cuff inflation, the cross then became black again.

Then, shortly before the cuff was deflated, the cross turned blue, signaling anticipation of relief from pain.

At each point, participants pushed buttons to report the intensity of pain and the associated unpleasantness. Simultaneous brain responses to anticipation, pain, and anticipation of relief were assessed on MRI.

Patients' mean age was 44, most were women, and symptoms had been present for 12.5 years. Baseline clinical pain intensity was rated as 34.3 on a 100-point scale, and pain unpleasantness was rated at 32.3.

The initial MRI scan assessed the entire brain, and found increased activation in multiple areas with the pain anticipation cue in both patients and controls, including the basal ganglia, thalamus, and the cerebellum. No differences were seen between patients and controls in anticipation of pain or relief in these whole-brain scans, however.

In addition, there were no significant differences for the nucleus accumbens. Only in the VTA region were there significant between-group differences, as seen using blood oxygen level-dependent functional MRI.

Also, responses to anticipation of pain among controls showed a negative correlation with responses in the VTA to anticipation of relief (r = 0.76, P=0.002). That correlation was not seen in patients with fibromyalgia (r = -0.12, P=0.52).

The VTA is intensely dopaminergic, and, while it has conventionally been thought to participate in reward signaling, it also appears to be involved in punishment and aversion signaling.

"Our observation that a region rich in dopaminergic neurons such as the VTA exhibits less reactivity ... is compatible with the results of other studies showing altered dopaminergic neurotransmission in fibromyalgia patients," the researchers wrote.

The finding that patients with fibromyalgia had diminished responses to painful stimuli in so-called reward regions of the brain may help explain the fact that they also don't typically respond to opioid-induced analgesia, the researchers noted.

Among the factors that may further explain the differences in brain activity in patients with fibromyalgia was a reduced level of activity in the midbrain periaqueductal gray, which helps regulate behavioral responses to pain. This suggested that patients also may have a diminished ability to upregulate brain-centered coping mechanisms.

A limitation of the study was a lack of correlating behavioral data.

http://www.medpagetoday.com/Rheumatology/Fibromyalgia/42729

Study Finds Blind People Hypersensitive to Pain - National Pain Report - National Pain Report

People who are born blind experience pain differently than sighted individuals and are hypersensitive to pain caused by hot or cold stimulation, according to a small study by researchers in Europe.

The results indicate that congenitally blind people are more attentive and more sensitive to external threats — suggesting their brains are "rewired" by their disability. The study is being published in the journal PAIN.

"We have shown that the absence of vision from birth induces a hypersensitivity to painful stimuli, lending new support to a model of sensory integration of vision and pain processing," says lead investigator Ron Kupers, Director of the BRAINlab, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences at the University of Copenhagen, Denmark.

The findings are important because a key biological function of acute pain is to prevent bodily injury. Vision plays a critical role, as it allows a person to immediately detect and avoid potentially hazardous situations.

Previous studies conducted in sighted individuals had already demonstrated the link between vision and pain perception. The research team hypothesized that the absence of visual cues may lead to heightened vigilance for painful stimuli.

Investigators recruited 11 congenitally blind and 15 sighted participants from Italy and a second group of 18 congenitally blind and 18 sighted participants from Denmark.

Researchers used thermal probes on the forearms of each participant to measure their thresholds for pain. The congenitally blind participants were allowed to touch the equipment beforehand and received verbal descriptions to reduce any anxiety. Sighted subjects were blindfolded during the actual testing.

Participants pushed a button whenever the thermal probe was hot or cold enough to cause pain. They also completed a questionnaire on their vigilance and awareness of pain.

The study team found that compared with sighted subjects, congenitally blind people had lower thresholds for pain caused by heat, rated heat pain as more painful, and had increased sensitivity to cold pain.

"The novel finding of pain hypersensitivity in blindness has several important implications for both basic and clinical science," said Flavia Mancini, PhD, Institute of Cognitive Neuroscience, University College in London.

"This study is noteworthy for research on multisensory interactions and plasticity, because it shows a strong link between vision and pain. The next step is to understand the nature of the interaction between visual loss and pain sensitivity. Which aspect of pain processing is involved in the interplay with vision, and what is its neural basis? The hope is that this work will open the door to pain investigations into the world of sensory loss, left unexplained for too long."

Interesting cultural differences also emerged from the study. People in Italy were found to be more emotionally expressive and responsive to pain than people in Denmark.

http://americannewsreport.com/nationalpainreport/study-finds-blind-people-hypersensitive-pain-8822248.html

Welcome | Cochrane Pain, Palliative and Supportive Care Group

Background

The PaPaS Review Group was registered with the Collaboration on the 28th January 1998. Exploratory meetings for the PaPaS Review Group were held on the 3rd of June 1996 (Oxford) and the 22nd of June 1997 (Boston). Mr Phil Wiffen was involved in the set-up of the PaPaS Review Group and held the post as Co-ordinating Editor until March 2008 when he stepped down to become an Editor for PaPaS. Chris Eccleston, one of our long standing Editors, then took up the post as Co-ordinating Editor in April 2008.

Scope

We are interested in studies of interventions for

• Acute pain arising accidentally or through deliberate injury

• Chronic pain (lasting 3 months or longer)

• Headache and migraine

• Palliative care for those with life-limiting disease or illness

By subtopic:

Acute pain (96)

Chronic non-cancer pain (67)

Headache and migraine (38)

Pain measurement tools (0)

Palliative and supportive care (85)

http://papas.cochrane.org/welcome 

Welcome | Cochrane Back Review Group

The Cochrane Back Review Group (CBRG) is one of 53 international Review Groups. The CBRG coordinates the publication of literature reviews of diagnosis, primary and secondary prevention and treatment of neck and back pain and other spinal disorders, excluding inflammatory diseases and fractures.

The CBRG is hosted by the Institute for Work & Health (IWH) in Toronto, Canada. The Institute for Work & Health is an independent, not-for-profit organization. Its mission is to conduct and share research that protects and improves the health of working people and is valued by policy-makers, workers and workplaces, clinicians, and health & safety professionals.

The Cochrane Collaboration, established in 1993, is an international network of more than 28,000 dedicated people from over 100 countries. The Collaboration works together to help health care providers, policy makers, patients and their advocates and caregivers, make well-informed decisions about health care, based on the best available research evidence, by preparing, updating and promoting the accessibility of Cochrane Reviews.

Cochrane Reviews are systematic reviews of primary research in human health care and health policy, and are internationally recognized as the highest standard in evidence-based health care. They investigate the effects of interventions for prevention, treatment and rehabilitation. They also assess the accuracy of a diagnostic test for a given condition in a specific patient group and setting. Cochrane Reviews are published online in The Cochrane Library.

http://back.cochrane.org/