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<div><p>Introduction</p><p>A patient’s perceived sensitivity to medicines (PSM) might influence the reported side effects of a treatment. The experience of side effects can result in personal and structural costs (such as nonadherence). Research on nocebo mechanisms and the workings of side effect reporting has been disproportionally smaller compared to the emerging evidence of the individual and clinical impact of the matter. In this study, we explored and re-examined the association between PSM and reported side effects within a specific population (chronic low back pain patients receiving acupuncture treatment), including possible mediating variables (i.e., gender, medical and nonmedical care utilization, optimism, pessimism, anxiety, depression and treatment expectation).</p><p>Methods</p><p>We conducted a secondary analysis of a randomized controlled trial that examined the influence of treatment outcome expectations in chronic low back pain (CLBP) patients. All measures in the analysis were self-assessments. We explored the association between PSM, reported side effects and personal characteristics using correlational and regression analyses.</p><p>Results</p><p>Our sample consisted of 152 CLBP patients (65.8% female), the mean age was 39.5 years (SD = 12.5). We found positive correlations between PSM and reported side effects (r = 0.24; p < 0.01) and between PSM and anxiety (r = 0.21; p < 0.05). However, the subsequent regression analyses did not confirm a mediating or moderating effect of anxiety between PSM and reported side effects.</p><p>Conclusion</p><p>We confirmed and extended earlier research on PSM. Our study involved a specific pain population receiving a nonpharmacological intervention. Our results highlight the importance of targeting PSM and anxiety within a treatment to take measures to mitigate the prevalence of side effects.</p></div>