• To document the types and frequencies of adverse reactions associated with the most common chiropractic treatments for neck pain, and to identify possible clinical predictors of adverse reactions to chiropractic treatment.

This study by Hurwitz et al from 2005 looked at the type and frequency of adverse events associated with chiropractic treatments for neck pain. Study participants were included if they had neck pain without progressive neurologic deficit or presence of disc herniations. Additionally they were excluded if they had evidence of myelopathy, spondyloarthropathy or were involved in litigation. Patients were randomized in 2 x 2 x 2 groups which included manipulation vs. mobilization, heat therapy vs. without heat therapy, and electrical stimulation vs. without electrical stimulation.

During the enrollment period, approximately 1000 patients were identified that could participate in the study.  Only 35% actually enrolled in the study.  Of the initial 336 enrolled patients that were randomized into the 6 subgroups,  280 (83%) returned surveys regarding adverse effects from their treatments.

Adverse events included neck pain, arm pain,  headache,  dizziness, nausea,  extremity weakness,  confusion and depression.

Based on the findings of the study, 30% reported some adverse effects from treatment within the first two weeks of treatment. There was no difference in reported adverse effects when controlling for heat or electrical stimulation..

Subjects who received manipulation had higher reports of adverse effects compare to those who had mobilization.

The authors concluded chiropractic care for neck pain will cause some adverse effects for 30% of the treated patients within the first two weeks. Manipulation has a higher percentage of adverse effects compared to mobilization.  Review of the patients who developed adverse effects indicates greater initial pain and neck disability index is associated with more adverse effects.

As a criticism, the authors compared the rate of adverse effects for chiropractic care versus more aggressive medical treatments such as surgery.  Based strictly on the scientific method,  the author should only make some general statements on adverse effects of other treatments.  The surgical patient profile is not comparable to chiropractic patients who do not have any radiculopathy or disk herniation.

The merit of the study is in its methodology. It was a blinded 2 x 2 x 2 study, of short duration and greater than 80% feedback.  It did demonstrate that 30% of patients undergoing chiropractic care for neck pain can expect some adverse reaction within the first two weeks.  It also showed manipulation may increase the incidence of adverse events compared to mobilization.

While the adverse effects are documented, we do not know anything about the efficacy of chiropractic care for the studied neck pain subjects, and whether these adverse effects are only a transient effect,  or if the adverse events caused inferior results for these subjects.