Adverse reactions to chiropractic treatment and their effects on satisfaction and clinical outcomes among patients enrolled in the UCLA Neck Pain Study

Background: Minor side effects associated with chiropractic are common. However, little is known about their predictors or the effects of reactions on satisfaction and clinical outcomes. Objective: The objectives of this study are to compare the relative effects of cervical spine manipulation and mobilization on adverse reactions and to estimate the effects of adverse reactions on satisfaction and clinical outcomes among patients with neck pain. Methods: Neck pain patients were randomized to receive cervical spine manipulation or mobilization. At 2 weeks, subjects were queried about possible treatment-related adverse reactions and followed for 6 months with assessments for pain and disability at 2, 6, 13, and 26 weeks. Numerical rating scales and the Neck Disability Index were used to measure pain and disability. Perceived improvement and satisfaction with care were assessed at 4 weeks. Results: Of 960 eligible patients, 336 enrolled and 280 responded to the adverse event questionnaire. Thirty percent of respondents reported at least 1 adverse symptom, most commonly increased pain and headache. Patients randomized to manipulation were more likely than those randomized to mobilization to report an adverse reaction (adjusted odds ratio = 1.44, 95% confidence interval = 0.85, 2.43). Subjects reporting adverse reactions were less satisfied with care and less likely to have clinically meaningful improvements in pain and disability. Conclusions: Adverse reactions are more likely to be reported following cervical spine manipulation than mobilization. Chiropractors may reduce iatrogenesis and increase satisfaction and perhaps clinical outcomes by mobilizing rather than manipulating their neck pain patients.