How Many Visits? Chiropractic Dose-Response Research

Author: Daniel Redwood, DC/Friday, January 08, 2016/Categories: September 2015

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By Daniel Redwood, DC

Doctors of chiropractic, chiropractic patients and employees of insurance companies that provide coverage for chiropractic services have wondered for years how many visits to a chiropractor are needed to achieve maximum patient benefit for the conditions DCs treat most often—low-back pain, neck pain and headaches. Until recently, the absence of research data addressing this question has meant that such decisions had to be based on personal experience (or economic influences) because no research had yet addressed the question.

Dose-response studies have long been seen as a necessity in the medical profession, as prescribing the correct dosage of a drug can spell the difference between appropriate and effective care on the one hand and death or serious injury on the other. For instance, proper dosage of an anticoagulant for a patient in the throes of a cerebrovascular event can prevent permanent damage, while an inadequate or excessive dose can leave some patients with permanent unilateral disabilities or complications from excessive bleeding. Similarly, dosage of insulin or other hypoglycemic medications is a critical element in ensuring proper blood sugar levels in diabetics and has potential dire short-term or long-term consequences if too high or too low a dosage is administered.

Excessive or inadequate courses of care with chiropractic physicians rarely, if ever, carry such alarming risks. Yet questions of over-treatment—and its mirror image, under-treatment—persist within the profession, among the patients who depend on chiropractic care and the insurers that in some cases pay for it.

As the late Jerome McAndrews, DC, a longtime ACA vice president of professional affairs and one of the leading political figures in the mainstreaming of chiropractic in the second half of the 20th century, wrote in the 1990s, “Duration of care is a major unresolved issue in chiropractic. Depending on which chiropractor a patient sees, the recommended course of care for the same condition may vary drastically, from several visits with one doctor to several dozen—sometimes hundreds—with another. Such variations appear in all regions, among graduates of all chiropractic colleges, and in urban, suburban and rural settings. Reducing these variations is crucial to the further advancement of the chiropractic profession.” (1) In the absence of solid evidence to guide chiropractic practitioners and educators as to proper dosage, such variation seems inevitable.

Dose-Response Studies

One of the ways researchers can help chiropractic practitioners increase the likelihood that they are neither over-treating nor undertreating their patients is to conduct dose-response studies that evaluate the outcomes of chiropractic services over a period of time, paying close attention to the number of visits utilized relative to the degree of positive outcomes achieved.

To date, the only chiropractic research teams to publish dose-response studies have been those led by Mitch Haas, DC, MA, a leading chiropractic researcher for more than two decades who serves as associate vice president for research at the University of Western States. Dr. Haas explains his decision to pursue dose-response studies this way: “There were several motivating factors. The first, of course, is what is best for the patient. Another is that there’s some ambiguity in efficacy and comparative effectiveness research on chiropractic, and when you look at the literature, you see that there’s no definitive number of visits used in randomized trials. So there are questions as to whether the comparative effectiveness of manipulation is being optimally measured. No one knew with any certainty what the optimal dose was to work with. There is also the issue of what is a reasonable amount of care that should be covered by insurance.”

Although insurance companies seeking to limit the amount they pay for chiropractic services may seek rationales for capping or limiting the number of visits to a doctor of chiropractic (DC), Haas’ group approached the question far more broadly. While acknowledging that some courses of chiropractic services may include more visits than what is required to achieve an optimum result, they pointedly note as well that the reverse may also be true. That is, DCs may be discontinuing care too soon.

Thus, critical questions related to quality of care and cost-effectiveness persuaded Haas’ group to pursue dose-response studies. They focused on two conditions in their work: low-back pain (LBP) and cervicogenic headache.

LBP was first on the priority list for a chiropractic dose-response research agenda, a position it has also occupied for many years in chiropractic research overall, due to the widespread prevalence of the condition and a broad-based recognition among policy makers and others that it constitutes a major public health problem.

Dose-Response Research: Low-Back Pain

The first dose-response publication related to chiropractic treatment of LBP appeared in 2004 in the Spine Journal. In this pilot study involving 72 people with chronic LBP, patients were assigned to receive one, two, three or four visits per week for three weeks.(2) Treatment regimens varied as well, consisting of either spinal manipulation alone or spinal manipulation with physical modalities, consisting of one or two of the following at each visit: soft-tissue therapy, hot packs, electrotherapy or ultrasound. Spinal manipulation in all cases included high-velocity, low-amplitude methods.

The results provided the first evidence-based peek into previously uncharted territory. The key dose-related finding was “a positive, clinically important effect of the number of chiropractic treatments for chronic low-back pain on pain intensity and disability at 4 weeks.” Pain relief was described as “substantial” for patients receiving care three to four times per week for three weeks. However, as is often the case with all types of care for chronic LBP, the noted effects diminished over time. At 12 weeks, there were no statistically significant differences among the groups receiving the different frequencies of visits.

Pilot projects are a necessary step toward larger, more robust studies. After completing the initial pilot, Haas’ group of investigators continued its work on LBP dose-response with a much larger study, a practice-based randomized trial involving 400 patients.(3) This time, 100 participants with chronic LBP were randomized to each of four dose levels of care: 0, 6, 12 or 18 sessions of spinal manipulation from a DC. Participants were treated three times per week for six weeks. At visits where no manipulation was delivered, a “focused light massage control” was provided.

The results of this study constitute the strongest currently available evidence on the number of visits needed to achieve an optimum response in the average case of chronic LBP. What the investigators found is that for chronic low-back pain, 12 visits yielded the most favorable results but was “not well distinguished from other dose levels.” When I interviewed Dr. Haas in 2015 and asked him to reflect on how his group’s findings over the past decade can best be interpreted by DCs and others, he replied:

“An important message is that some chiropractors are over-treating. Except in rare cases, if you’re treating 30 or 40 visits, that’s over-treating. But a key take-home message is that some people might be treating too little. In a practice-based comparative study many years ago (ref), we found that chiropractors were on average only seeing patients three or four times. So they’re seeing patients until they feel that they’re better, which is not unreasonable. But what is not clear is whether continuing beyond that wouldn’t actually have some benefit in the long run. If you keep adjusting even though the pain may be gone, in the longer term it may have some benefit.”

A study conducted at the Monsoura University in Egypt, published in Spine in 2011, supports the value of phased-down continued care after the initial treatment phase has been completed.(4) In what remains the only published study of its kind, researchers Senna and Machaly examined the effectiveness of maintenance spinal manipulation in long-term reduction of pain and disability levels associated with chronic low-back conditions after an initial phase of treatments. Sixty patients with chronic, nonspecific LBP lasting at least six months were randomized to receive either: (1) 12 treatments of sham SMT over a one-month period; (2) 12 treatments, consisting of SMT over a one-month period but no treatments for the subsequent nine months; or (3) 12 treatments over a one-month period, along with “maintenance spinal manipulation” every two weeks for the following nine months. Patients in the second and third groups experienced significantly lower pain and disability scores than the first group at the end of one month. Only the third group, which received maintenance manipulation during the follow-up period, showed more improvement in pain and disability scores at the 10-month evaluation. In the non-maintained SMT group, however, the mean pain and disability scores returned to levels close to their pretreatment level.

Returning to the series of papers by Haas’ et al., their most recent publication(5) addressed cost-effectiveness related to dose response for spinal manipulation for chronic LBP. The key finding on this economically and politically sensitive issue is that 12 chiropractic sessions with spinal manipulation “can have a modicum of benefit in LBP-related pain and disability without significantly increasing treatment or societal costs.” In other words, the financial gain from an early return to work balances out the financial loss related to the cost of chiropractic treatment.

Dose-Response Research: Cervicogenic Headache

The second series of dose-response studies by Haas and colleagues explored the efficacy related to dose response in cases of cervicogenic headache (CGH), with funding including grant support from the NIH National Center for Complementary and Alternative Medicine [now renamed the National Center for Complementary and Integrative Health (NCCIH)]. The initial pilot study, published in the Journal of Manipulative Therapeutics in 2004, was a randomized trial involving 24 adults with CGH. In this clinical trial, the investigators found that “there was a substantial benefit in pain relief for 9 and 12 visits compared with 3 visits.” This is consistent with the number of visits used in some previous chiropractic-related headache trials that demonstrated a clinical benefit from manipulation, such as those by Boline(6) and Nelson.(7)

Bolstered by these findings in the pilot study and seeking to more finely calibrate the most effective dose for chiropractic treatment of CGH, a larger trial with 80 patients was undertaken, with the results published in Spine Journal in 2010.(8) Participants were randomized to either eight or 16 treatment sessions with either SMT or a minimal light-massage control. Patients were treated once or twice per week for eight weeks. As noted by the editors of Spine Journal,“ The authors have found in the patient population studied that CSMT [chiropractic spinal manipulative therapy] administered to the cervical and upper thoracic spine resulted in a significantly greater improvement in pain scores when compared to a control group that received light massage” and that “there was no significant difference in patient outcomes in patients who received 8 or 16 CSMT treatments.” However, the authors noted that the treatment effect was likely greater at the higher dose. A full-scale randomized trial is in progress.

DCs Can Utilize These Findings to Optimize Patient Care and to Ensure Fairness From Insurance Companies

In an era when all health professions profess to value patient-centered care, the initial response by individual chiropractors to this dose-response research should involve an introspective look at our own practice patterns. This must include a willingness to adjust our approaches when solid evidence justifies such changes, in the interest of our patients. For insurance companies, the response should be a thoroughgoing analysis of how to achieve the best possible health outcomes for their subscribers, not how to maximize profits by minimizing care. Admittedly, if applied in the interest of achieving justice, both practitioners and insurers need to make some decisions that may have an adverse impact on their bottom lines, at least in the short run. The role of policy makers (legislators and regulators) should be to ensure justice for the public they are sworn to serve.

It is essential to note that the data from these important dose-response studies, particularly the conclusions related to the optimum number of visits, apply to the average case, not to all cases. Thus, eight visits for cervicogenic headache or 12 visits for chronic low-back pain should be interpreted neither as a hard ceiling by insurers nor as a minimum course of care for all cases by DCs. Patient-centered care is individualized care. Having a general sense of what is most effective for most patients is very helpful but was never intended by researchers to be applied to all patients in rote cookie-cutter fashion, either by practitioners or by the corporations that in many cases control the purse strings.

For chiropractic physicians seeking to promote and defend our healing art with evidence from well-designed research studies in a manner consistent with justice for all, dose-response studies can prove a valuable tool. May we all use them responsibly and assertively.


  1. McAndrews JF. Appropriate Care, Ethics, and Practice Guidelines. In: Redwood D, Cleveland CS, 3rd, eds. Fundamentals of Chiropractic. St. Louis: Mosby; 2003:603-611.

  2. Haas M, Groupp E, Kraemer DF. Dose-response for chiropractic care of chronic low back pain. Spine J. 2004;4(5):574-583.

  3. Haas M, Vavrek D, Peterson D, Polissar N, Neradilek MB. Dose-response and efficacy of spinal manipulation for care of chronic low back pain: a randomized controlled trial. Spine J. 2014;14(7):1106-1116.

  4. Senna MK, Machaly SA. Does maintained spinal manipulation therapy for chronic nonspecific low back pain result in better long-term outcome? Spine. 2011;36(18):1427-1437.

  5. Vavrek DA, Sharma R, Haas M. Cost analysis related to dose-response of spinal manipulative therapy for chronic low back pain: outcomes from a randomized controlled trial. JMPT. 2014;37(5):300-311.

  6. Boline PD, Kassak K, Bronfort G, Nelson C, Anderson AV. Spinal manipulation vs. amitriptyline for the treatment of chronic tension-type headaches: a randomized clinical trial. JMPT. 1995;18(3):148-154.

  7. Nelson CF, Bronfort G, Evans R, Boline P, Goldsmith C, Anderson AV. The efficacy of spinal manipulation, amitriptyline and the combination of both therapies for the prophylaxis of migraine headache. JMPT. 1998;21(8):511-519.

  8. Haas M, Spegman A, Peterson D, Aickin M, Vavrek D. Dose response and efficacy of spinal manipulation for chronic cervicogenic headache: a pilot randomized controlled trial. Spine J. 2010;10(2):117-128.

The key finding on this economically and politically sensitive issue is that 12 chiropractic sessions with spinal manipulation “can have a modicum of benefit in LBP-related pain and disability without significantly increasing treatment or societal costs.”

It is essential to note that the data from these important dose-response studies, particularly the conclusions related to the optimum number of visits, apply to the average case, not to all cases.

Daniel Redwood, DC, is director of the all-online Master of Human Nutrition and Functional Medicine program at the University of Western States. His 10-hour series of online continuing education courses, Defending Chiropractic: Using Research to Defend and Promote Chiropractic, can be accessed at


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