The Impact of Psychological Factors on Nociplastic Pain: A Comparative Analysis of Alexithymia, Defense Mechanisms, and Trauma Across Different Conditions

Background and Aims: To better comprehend the etiology of chronic pain (CP), IASP has proposed the label of Nociplastic Pain (NP) which encompasses conditions resulting from altered nociception without clear evidence of actual or threatened tissue damage. NP encompasses clinical conditions with common neurophysiologic mechanisms, such as fibromyalgia (FM), chronic headache (CH), and vulvodynia (VU). One possible mechanism underlying NP is Central Sensitivity (CS), defined as an increased responsiveness of nociceptive neurons in the central nervous system to normal or subthreshold inputs. Literature has linked CS to psychological factors, whose central role in CP conditions is recognized. However, the specific role of these factors in each chronic condition is still unclear, just as there is a lack of studies comparing psychological variables in patients with various CP both in isolation and in comorbidity. This study aims to compare the impact of psychological factors (traumatic experiences, defense mechanisms, and alexithymia) between different CP conditions, in particular: CH FM, VU, mixed diagnoses (MX; consisting of FM in comorbidity with CH and/or VU), and a control group (HC). Methods: 1006 women (n=195 CH, n=186 FM, n=193 VU, n=315 MX, n=117 HC) completed a selfadministered online protocol. ANCOVA, MANCOVA, and Bonferroni post hoc tests were performed with age as a covariate. Results: Significant differences were found among the five groups in the variables examined: traumatic experiences (F = 12.710; p < 0.001), alexithymia (F = 10.819; p < 0.001), and neurotic defenses (F = 10.991; p < 0.001). Bonferroni post hoc tests showed that MX, compared with the other conditions, is more characterized by a childhood history of trauma (especially neglect and emotional abuse). In addition, both MX and FM differed from the other groups in significantly higher scores in both the inability to identify feelings and the use of neurotic defensive strategies. Conclusions: Traumatic experiences, particularly emotional neglect and physical threats may contribute to the development and worsening of CP conditions, especially in individuals with comorbidities. Moreover, FM and MIX show a greater tendency for neurotic defenses and greater alexithymia, underscoring the impact of emotional processing difficulties on the manifestation of CP.