Autistic traits in fibromyalgia are associated with hypersensitivity and central sensitisation.

Fibromyalgia presents with symptoms of central sensitisation (CS). Allodynia is the defining symptom, with evidence for general hypersensitisation extending beyond the pain symptoms that characterise fibromyalgia, to sensory and psychological domains. Generalised sensory processing sensitivity (SPS) may increase vulnerability to hypersensitisation; while a direct association exists between sensory sensitivity and autistic traits in autistic people, CS symptoms are also associated with autistic traits in a broader participant sample. This study complements previous lines of enquiry by examining the relationship between SPS, CS symptoms and autistic traits in samples with and without fibromyalgia. It proposes that SPS is indirectly associated with autistic traits via CS and that this association is stronger in fibromyalgia because CS symptoms impact social, physical and psychological functioning. A sample was diagnosed with fibromyalgia (n = 260) and another from the general population (n = 139) completed the Sensory Processing Sensitivity Questionnaire, a measure of sensory and psychological sensitivities, the Central Sensitisation Inventory, a measure of CS symptoms, and the Subthreshold Autistic Traits Questionnaire. Higher levels of SPS, CS symptoms and autistic traits were reported in the sample with fibromyalgia, and all three factors were significantly positively correlated. As predicted, CS symptoms fully mediated the relationship between SPS and autistic traits in the sample with fibromyalgia, and less expectedly, also in the control. Participant samples moderated the relationship between CS symptoms and autistic traits, with autistic traits increasing more rapidly with CS symptoms in the sample with fibromyalgia. Results suggest autism may be prevalent in people with fibromyalgia, particularly those with extremely high levels of CS symptoms. However, clinicians should also be aware of the potential to misdiagnose autism in this population, as CS symptoms may elevate self-reported autistic traits.