The Influence of Cognitive Processes on Pain Perception

Cognitive and emotional influences on the perception of pain constitute a complex emotional experience that varies significantly from one individual to the next.

Psychological state can play a role in the success of pain treatment: a negative emotional state and low expectation of treatment success can increase the intensity of the pain experienced, and dampen the analgesic effect of a clinical dose of an opioid analgesic. In contrast, a positive emotional state and a positive expectation of pain relief can lower pain and enhance clinical effect of treatment. This phenomenon is thought to be involved in the placebo effect of analgesia.^1-3

In fact, placebo analgesia is increasingly regarded as a legitimate pain control modality, influenced by cognitive processes, and which can be modulated through education and learning. A recent review by Katja Wiech, PhD, a postdoctoral fellow at the Functional Magnetic Resonance Imaging of the Brain Centre at the Univeristy of Oxford, provides a comprehensive analysis of the influence of cognitive processes on pain perception, and its potential integration into the management of chronic pain.⁴

Functioning by distraction while in pain is a common coping mechanism. In fact, evidence indicates that pain perception may be attenuated when the individual performs cognitive tasks or is distracted.^5,6 A study demonstrated that even in the presence of mild to moderate pain intensity, cognitive-related activity is minimally affected, and individuals instructed to complete a task, will do so, despite the pain.⁵ Distraction therapy as a coping strategy for chronic pain control, supported by evidence from brain imaging studies, and audiovisual distraction techniques, has successfully been used in both pediatric and adult patients.^6-9 

Pain control through distraction, educational intervention and verbal manipulation demonstrates the powerful influence of cognition on pain sensation and provides a tool to untangle the mechanisms of placebo analgesia. Patients with chronic musculoskeletal pain and exposed to active educational intervention, greatly improved their perceptions of placebo knowledge, its effectiveness and its acceptability as a viable treatment option, compared to patients presented with a placebo educational intervention.¹⁰

Verbal manipulation was also shown to improve both perception and expectation of pain, possibly by reducing activity in the “pain matrix,” an approach akin to placebo analgesia.^4,11 Studies in animals and human subjects indicate that expectation can introduce bias in the perception of pain by modulating activity in brain areas involved in sensory processing, but also, in regions associated with the interpretation of the information.¹²

Understanding the mechanisms underlying placebo analgesia may help explain the influence of cognitive and psychosocial processes on pain perception. While placebo research is still scarce, mounting evidence implicates complex biological processes and mechanisms, thus questioning  the historical view that placebo response is only achieved by deception and as such, should be minimized or avoided in clinical practice.¹³

Indeed research has revealed that key regions of the brain – the frontostriatal and descending pain control systems — are sensitive to both pain perception and cognitive manipulation. It has been postulated that the frontostriatal system is involved in the conversion of nociception to perception of pain as well as in the transition from acute pain to chronic pain.^14,15

Activation and functional connectivity between the descending pain control system, comprising the dorsolateral prefrontal cortex, the rostral anterior cingulate cortex, and periaqueductal gray, positively correlates with pain relief, reduces activation of other pain-related regions of the brain, and is thought to also play a role in cognitive manipulations such as distraction, all of which contribute to pain reduction.^4,16,17  

The variation in pain perception between individuals, particularly among chronic pain patients, appears to be related to the degree of structural and functional connectivity between these specific brain regions.^18,19 A key question that has potential clinical implications is whether the known influence of cognition on pain perception can be willingly manipulated as part of a pain treatment strategy to achieve radical and maximum pain relief.

Although a theoretical possibility, in reality, there are limits to the degree to which cognition can influence perception of sensory signals.²⁰ Treatment experience, expectation of outcome, and information received through education, all play a role to impact a patient’s adherence to a treatment program, and to some extent, influence subsequent treatments.³ Therefore treatment success, be it with a placebo or an active analgesic, is often dependent on patients expectations and influenced by information provided to them by their healthcare provider.

While advances are being made to better characterize the influence of cognitive processes on pain perception, research is still in its infancy, and current evidence raises more questions that can only be answered with continued research. For example, the nature of the trigger for cognitive pain modulation, and the factors that can stop it remain unclear. These cognitive influences and the perceptual process that gives rise to the experience of pain are also ill-understood.

Research is also needed to guide the development of a coherent model that incorporates behavioral and neuroimaging evidence, so as to address all aspects of cognitive modulation, including its initiation, implementation, and monitoring.⁴