Our review has limitations. First, the evidence for our primary outcomes was only of very low certainty, which limits the strength of inferences from our results. Second, although pain severity, symptom duration, chiropractic visit frequency, and type of opioid prescriber(s) (eg, general practitioner vs specialist/Emergency Department physician) may influence treatment effects, [28] there was either insufficient data or lack of variability among included studies to explore these issues. Third, most of our data were from observational studies, and patients accessing chiropractic services may be more resistant to using opioids than those not receiving chiropractic care. [26, 27]
Fourth, all studies eligible for our review enrolled patients presenting for care in North America, and the generalizability of our findings to other jurisdictions is unclear. Finally, we only included studies with outcome data for opioid use. As such, we did not capture all RCTs and observational studies investigating the impact of chiropractic care on other patient-important outcomes, including pain intensity, physical functioning, patient satisfaction, and adverse events.