Is chiropractic treatment safe and effective? [duplicate]

Question

Has there been any reliable independent studies into the efficacy of chiropractic treatment and claims that it can either cure or provide significant relief from mechanical disorders?

Is there any reported data to suggest a greater number of people receive injury as a result of treatment by a chiropractor when compared to other medical professions?

Is chiropractic treatment high risk?

According to a statement in this wikipedia article:

A 2010 systematic review stated that there is no good evidence to assume that manipulation to the neck is an effective treatment for any condition and thus concluded, "the risks of chiropractic neck manipulations by far outweigh their benefits."

and

A 2009 review evaluating maintenance chiropractic care found that spinal manipulation is routinely associated with considerable harm and no compelling evidence exists to indicate that it adequately prevents symptoms or diseases, thus the risk-benefit is not evidently favorable

Answer 1

The question "is chiropractic treatment effective?" is quite wide, as this type of treatment is proposed for several different illnesses, from neck or back pain to headache even to gastrointestinal problems. Furthermore, as for many alternative treatments, they are often proposed by a wide variety of persons, from people with medical degrees (more or less related to the field), to people who attended chiropractic colleges, to charlatans... and obviously the results (and the side effects) vary accordingly.

Now, you cited two Wikipedia links that analyze negative effects of this type of treatment.

The 2009 study is a bit misinterpreted in Wikipedia as it refers to spinal injuries in students of a chiropractic college.

Prevalence of musculoskeletal injuries sustained by students while attending a chiropractic college.

Although we cannot conclude much about the efficacy of the treatment from this study (as it was administered by students), it clearly proves the point that an uncompetent chiropracter can harm his/her patient.

From the conclusions of the paper (parts in italics are my additions)

This study shows that some students who enroll in a chiropractic college with preexisting injuries can have these injuries exacerbated during training. A recognizable amount of new incidences are possible as a result of the adjustments they administer or receive from other students. The most prevalent injuries from receiving adjustments occur to N/S [neck-shoulder], whereas those due to administering adjustment occur to H/W [hand-wrist]. Only a few of the injuries sustained in college were severe to the extent of inhibiting the performances of normal daily work.

Some other severe side effects of chiropractic treatments have also been reported

Acute spinal epidural haematoma causing cord compression after chiropractic neck manipulation: an under-recognised serious hazard?

Bilateral vertebral artery dissection after chiropractic maneuver.

Simultaneous bilateral internal carotid and vertebral artery dissection following chiropractic manipulation: case report and review of the literature.

Note that these are very serious side effects, which are clearly not acceptable in a risk-benefit balance for treating neck-ache or similar problems. We should, however, also consider that -although very serious- these side effects are generally rare. As the first of these three papers concludes:

Spinal manipulation is a treatment performed by chiropractors, some orthopaedic surgeons and general practitioners in the UK. It is clear that the rarity of traumatic spinal epidural haematoma makes it difficult to establish cause-and-effect connections though the potential serious risks of high-spinal manipulations, however small and including vertebral artery dissection, should be communicated and discussed during consenting of patients.

A similar conclusion was drawn by a 2003 literature meta-analysis, which was inconclusive regarding artery dissection:

Association of internal carotid artery dissection and chiropractic manipulation.

The medical literature does not support a clear causal relationship between CMT and ICAD. Reported cases are exceedingly scarce, and none support clear cause and effect.

Furthremore, a 2005 literature meta-analysis states that

Perceived causation of reported cases of cervical artery dissection is more frequently attributed to chiropractic manipulative therapy procedures than to motor vehicle collision related injuries, even though the comparative biomechanical evidence makes such causation unlikely. The direct evidence suggests that the healthy vertebral artery is not at risk from properly performed chiropractic manipulative procedures.

Cervical artery dissection. A comparison of highly dynamic mechanisms: manipulation versus motor vehicle collision

Another recent (2011) study showed minimal effects on chest deformation using a dummy as a test subject

An experimental study of chest compression during chiropractic manipulation of the thoracic spine using an anthropomorphic test device.

So, do these treatment have any efficacy that can justify the risk of these (albeit rare) side effects?

A 2013 clinical trial (Short-term usual chiropractic care for spinal pain: a randomized controlled trial.) reports that:

Short-term chiropractic treatment was superior to sham; however, treatment effects were not clinically important. Awareness of treatment assignment and clinically important reductions in pain were associated with chiropractic treatment satisfaction.

The same authors report that (Outcomes of usual chiropractic. The OUCH randomized controlled trial of adverse events.)

A substantial proportion of adverse events after chiropractic treatment may result from natural history variation and nonspecific effects.

Furthermore, "A Cochrane review of manipulation and mobilization for mechanical neck disorders." reports:

Mobilization and/or manipulation when used with exercise are beneficial for persistent mechanical neck disorders with or without headache. Done alone, manipulation and/or mobilization were not beneficial; when compared to one another, neither was superior. There was insufficient evidence available to draw conclusions for neck disorder with radicular findings. Factorial design would help determine the active agent(s) within a treatment mix.

Regarding gastrointestinal problems the efficacy of chiropractic treatment could not be proven

Chiropractic treatment for gastrointestinal problems: a systematic review of clinical trials.

Only two trials were found--one was a pilot study, and the other had reached a positive conclusion; however, both had serious methodological flaws. There is no supportive evidence that chiropractic is an effective treatment for gastrointestinal disorders.

Finally, the 2010 study linked by Wikipedia, which analyzes deaths after chiropractic treatment.

Deaths after chiropractic: a review of published cases.

From the article

Twenty six fatalities were published in the medical literature and many more might have remained unpublished. The alleged pathology usually was a vascular accident involving the dissection of a vertebral artery

and (bold is mine)

In conclusion, numerous deaths have been associated with chiropractic neck manipulations. There are reasons to suspect that under-reporting is substantial and reliable incidence figures do not exist. The risks of chiropractic neck manipulations by far outweigh their benefits. Healthcare professionals should advise the public accordingly.

Answer 2

So, to completely counter the currently accepted result (as of 4 Jan 2012, anyway), a new study from the Annals Of Internal Medicine shows that chiropractic and neck exercises is a more effective treatment for neck pain than drugs (NSAIDs or narcotics). For instance:

For pain, SMT [Spinal Manipulation Therapy] had a statistically significant advantage over medication after 8, 12, 26, and 52 weeks (P ≤ 0.010), and HEA [Home Exercise With Advice] was superior to medication at 26 weeks (P = 0.02). No important differences in pain were found between SMT and HEA at any time point. Results for most of the secondary outcomes were similar to those of the primary outcome.

As the abstract further states, the patients couldn't be blinded (ie, no placebo chiropractic or home exercise treatments could be done), so it's tricky in the sense of traditional blinding to produce accepted results.

Furthermore, it's important to try to determine which kind of chiropractic therapy will be done. This article discusses the chiropractic theory of subluxation, and proceeds to debunk it:

Chiropractors have been adjusting vertebral subluxations since 1895 when D. D. Palmer, a magnetic healer, declared that "95% of diseases are caused by displaced vertebrae; the remainder by luxations of other joints." [10] ... Although some chiropractors no longer support the vertebral subluxation theory [13], the theory is still being taught in chiropractic colleges and still forms the basis for the average chiropractor's practice. There is no scientific evidence to indicate that vertebral misalignment or any dysfunction in structures of the spinal column is a cause of disease [14].

The article continues, with the ultimate conclusion:

As long as the chiropractic profession continues to base chiropractic treatment on the unproven vertebral subluxation theory, there will continue to be opposition from medical scientists as well as criticism by consumer advocates... Failure of chiropractors to criticize the pseudoscience in chiropractic (concentrating more on public relations than on promoting public health) perpetuates chiropractic dogma and fails to challenge chiropractors who exploit spinal manipulation.

So, so long as the chiropractor isn't using subluxation, it may have more health benefits than @nico's answer would lead me to believe.