In this study from The Journal of Alternative and Complementary Medicine, people with back pain were sent to chiropractors or pain clinics.  The results were compared.

People who went to chiropractic doctors had better pain relief than the people who went to pain doctors.

At 8 weeks, the mean improvement in RMDQ was 5.5 points greater for the chiropractic group (decrease in disability by 5.9) than for the pain-clinic group…

and,

This study suggests that chiropractic management administered in an NHS setting may be effective for reducing levels of disability and perceived pain during the period of treatment for a subpopulation of patients with CLBP.