In the general US population, an estimated 35 to 75 million people are said to report chronic pain (CP)—pain persisting for at least six months [3]. A common side-effect observed in patients with CP is cognitive impairment [3], a condition involving deficits in certain brain functions, such as memory, attention, executive functions, emotion regulation, and psychomotor speed [1,3,4,5,7].
Several researchers have aimed to explain the link between chronic pain and cognitive impairment. According to Roth et al., “depression is the most common comorbid psychologic problem associated with chronic pain,” suggesting that “the presence of depressive symptoms, particularly negative affect, is a primary source of cognitive disturbance for chronic pain patients” [5]. While cognitive impairment has been observed in patients suffering from depression and anxiety without CP [3], individuals living with CP, especially older adults, have been shown to have greater risk of developing depression [2]. Thus, depression is often considered a predictor of cognitive impairment among patients with CP, and “may provide the strongest explanatory power in understanding these complaints for this population” [5].
Similarly, “pain-related negative emotions and stress potentially impact cognitive functioning independent of the effects of pain intensity” [3]. In fact, studies show that “psychologic distress and negative emotions are more closely associated with cognitive deficits in patients with chronic pain than is pain severity” [3], as the brain networks that manage stress and emotion overlap with those that manage pain [3,7]. Roth et al. note that patients who “catastrophize” (or dwell on intensely) about their pain tend to be at greater risk for experiencing cognitive complaints, further emphasizing the impact of emotions on cognitive performance [5].
In addition to negative emotion and stress, other “concomitants of chronic pain, such as mood change, sleep disturbance, fatigue, and other aspects of suffering (e.g., lifestyle interference secondary to disability),” appear to be highly associated with cognitive impairment [3]. To better understand the relationship between CP and cognitive impairment, some researchers have focused their attention on fibromyalgia [7], a syndrome “characterized by widespread pain, constant tiredness, and non-restorative sleep” [7]. An estimated 50% of patients with fibromyalgia experience cognitive impairment [7], leading some researchers to associate sleep-disturbance and fatigue with cognitive dysfunction [5,7].
Memory and attention are often reported as the most affected cognitive functions in patients with chronic pain [1,3,4,5]. Previous studies indicate that patients with fibromyalgia “have consistent problems with immediate and delayed memory, attentional information processing, and psychomotor speed” [5]. It has also been suggested that “pain captures attention and consumes part of the patient’s attentional resources, thus impairing cognitive functioning” [7].
While it is generally accepted that chronic pain can cause adverse changes in cognitive functioning, the reasons explaining this relationship remain inconclusive [5]. However, most researchers agree on the importance of treating chronic pain as means to help prevent cognitive impairment [6].
References
1. Bartel, A., Jordan, J., et al. (2020). Somatic Burden and Perceived Cognitive Problems in Trauma‐exposed Adults with Posttraumatic Stress Symptoms or Pain. Journal of Clinical Psychology, 76(1), 146–160. DOI: 10.1002/jclp.22855
2. Condon, S. E., Parmelee, P. A., et al. (2021). Examining Emotional Intelligence in Older Adults with Chronic Pain: A Factor Analysis Approach. Aging & Mental Health, 25(2), 213–218. DOI: 10.1080/13607863.2019.1673308
3. Hart, R.P., Wade, J.B., et al. (2003). Cognitive Impairment in Patients with Chronic Pain: The Significance of Stress. Current Science Inc, 7,116–126 (2003). DOI: 10.1007/s11916-003-0021-5
4. Moriarty, O., Ruane, N., et al. (2017). Cognitive Impairment in Patients with Chronic Neuropathic or Radicular Pain: An Interaction of Pain and Age. Frontiers in Behavioral Neuroscience, 1–13. DOI: 10.3389/fnbeh.2017.00100
5. Roth, R. S., Geisser, M. E., et al. (2005). Cognitive Complaints Are Associated with Depression, Fatigue, Female Sex, and Pain Catastrophizing in Patients with Chronic Pain. Archives of Physical Medicine and Rehabilitation, 86(6), 1147–1154. DOI: 10.1016/j.apmr.2004.10.041
6. Rouch, A., Laurent, B., et al. (2021). Association Between Chronic Pain and Long-term Cognitive Decline in a Population-based Cohort of Elderly Participants. Pain, 162(2), 552–560. DOI: 10.1097/j.pain.0000000000002047
7. Samartin-Veiga, N., González-Villar, A. J., et al. (2019). Neural Correlates of Cognitive Dysfunction in Fibromyalgia Patients: Reduced Brain Electrical Activity During the Execution of a Cognitive Control Task. NeuroImage: Clinical, 23. DOI: 10.1016/j.nicl.2019.101817