The Illness Belief Network Questionnaire: Development and Evaluation of a Psychosomatic Assessment Tool.

Objective: Patients' beliefs and emotions toward an illness can influence their coping responses, illness behaviors, adherence to treatment, quality of life, and even the psychoneuroimmune responses. The aim of present study was to develop and validate a novel questionnaire assessing both rational and irrational beliefs of patients regarding their illness. Method : In a cross sectional methodological study, the items of the Illness Belief Network (IBN) were developed regarding patients and clients' opinions about and attribution of their disease extracted from 400 clinical interviews and were coded based on Leventhal's self-regulation model. An expert panel coded the items. A total of 400 patients with different medical conditions completed the questionnaire. Participants additionally rated the Illness Perceptions Questionnaire in its revised form (IPQ-R) to assess convergent validity. Construct validity was examined by conducting exploratory and confirmatory factor analysis. The Cronbach alpha and Intracluster Correlation Coefficient (ICC) were used for examining Internal consistency and test-retest reliability of the IBN. Results: The IBN questionnaire was finalized with 84 items, and the results of factor analysis revealed 5 factors: psychosocial causes, environmental causes, control, meaning, and consequence/timeline; extracted factors were confirmed by confirmatory factor analysis. Cronbach's α coefficient for scale was 0.92 and it ranged from 0.79 to 0.89 for the subscales. IBN indicated excellent test-retest reliability results based on ICC 0.842(95%CI: 0.798-0.846). The correlation coefficients of all items exceeded the prespecified acceptable value of 0.40, indicating satisfactory item discriminant validity, and correlation between IBN and IPQ-R subscales were statistically significant (all p values < 0.01), indicating acceptable convergent validity. Conclusion: The IBN questionnaire is a valid and reliable phenomenological, non-judging, and clinical tool to assess patient's rational and irrational or faith-based beliefs about the illness. This tool can be used to improve doctor-patient communication by exploring the complex nature of human thinking.