Illness Perception as a Key to Understanding Illness Severity in Fibromyalgia: A Cluster-Analytic Approach.

OBJECTIVE: Illness perception refers to the cognitive and emotional framework through which individuals interpret and respond to their health condition. It has been consistently linked with a range of health outcomes across various medical diagnoses. This association is particularly relevant in chronic pain syndromes such as fibromyalgia, where the inherently subjective nature of the condition and its susceptibility to psychological factors amplify the role of personal beliefs. While illness perceptions in fibromyalgia have been examined, it remains unknown whether individuals diagnosed with fibromyalgia differ systematically in their illness perceptions, and how such heterogeneity relates to disease severity. To address this gap, the present study aimed to examine whether distinct illness perception profiles exist among individuals with fibromyalgia and evaluate their association with symptom severity and overall health. METHODS: Across two independent cohorts, a total of 213 fibromyalgia patients completed the Illness Perception Questionnaire (IPQ), Fibromyalgia Impact Questionnaire (FIQ) and Self-Rated Health (SRH). Principal component and clustering analysis were performed to classify patients into different clusters. Additionally, analyses of variance were used to assess differences in disease severity and general health between the clusters. RESULTS: In both cohorts, three statistically distinct profiles of illness perceptions emerged. These profiles exhibited significant differences in disease severity and general health. CONCLUSIONS: Illness perceptions are heterogenous among fibromyalgia patients and this heterogeneity carries great relevance to clinical outcomes. Identifying distinct illness perception profiles may inform the development of personalized interventions that target specific cognitive and emotional representations of illness, ultimately improving patients' quality of life.