Potential publication bias in chiropractic and spinal manipulation research listed on clinicaltrials.gov.

Introduction: Clinical trial registries are used to help improve transparency in trial reporting. Our study aimed to identify potential publication bias in chiropractic and spinal manipulation research by assessing data drawn from published studies listed in clinincaltrials.gov.

Methods: We searched the clinicaltrials.gov registry database for completed trials tagged with the key indexing terms chiropractic or spinal manipulation. We assessed if the trial registry had been updated with data, then searched for publications corresponding to the registered trials. Finally, the frequency of positive or negative results was determined from published studies.

Results: For the term 'chiropractic', 63% of studies supported the intervention and 52% supported the intervention for the term 'spinal manipulation'.

Discussion: Publication bias in chiropractic and spinal manipulation research listed in clinicaltrials.gov appears to occur. Further work may help understand why this happens and what may be done to mitigate this moving forward.