Impact of different treatments for chronic pain on cognitive function: A systematic review

Experimental evidence supports the hypothesis of reciprocal influence between neural systems involved in cognition and central pain processing circuits. Furthermore, studies have demonstrated bidirectional communication between central pain processing areas and the immune system, leading to changes in behaviour, sensory perception, mood, and cognition. However, the academic community has not yet reached a consensus on whether effective analgesic interventions can mitigate or reverse cognitive deterioration.

This systematic review evaluated the effectiveness of various therapeutic interventions in improving cognitive functions (primary outcome) and altering the profile of immunological markers (secondary outcome) in chronic pain patients. The review was limited to randomised controlled trials addressing chronic pain of any aetiology, with searches conducted in PubMed, EMBASE, and Scopus databases.

The qualitative synthesis of twelve studies conducted between 2003 and 2021, involving 1432 participants in experimental (n = 950) and control (n = 482) groups, revealed some interesting patterns. Only half of the studies (6/12) reported cognitive improvement, with attention being the most analysed cognitive domain, followed by memory and executive function. Fibromyalgia was the most studied aetiology of chronic pain. The strategies of intervention/treatment and durations varied widely; however, milnacipran versus placebo emerged as the most frequently employed intervention. Only one study reported immunological markers, limiting the evaluation of this outcome.

Based on this analysis, it is not possible to affirm that interventions targeting chronic pain improve cognition. This review suggests new research directions and calls for more robust methodological approaches.