title: The outcome of control groups in clinical trials of conservative treatments for chronic mechanical neck pain: a systematic review.
abstract: BACKGROUND
  Chronic neck pain is highly prevalent in Western societies, with about 15% of females and 10% of males suffering with it at any time. The course of untreated chronic neck pain patients in clinical trials has not been well-defined and the placebo effect has not been clarified.
  
  
  METHODS
  A systematic review of RCT's of conservative treatments for chronic mechanical neck pain was conducted. Studies were excluded if they did not include a control group, if they involved subjects with whiplash injuries, a predominance of headache or arm pain associated with chronic neck pain and if only one treatment was reported. Only studies scoring 3-5 out of 5 on the Jadad Scale for quality were included in the final analysis. Data on change in pain scores of subjects in both placebo (PL) as well as no-treatment (NT) control groups were analyzed. Mean changes in pain scores as well as effect sizes were calculated, summarized and compared between these groups.
  
  
  RESULTS
  Twenty (20) studies, 5 in the NT group and 15 in the PL group, with outcome intervals ranging from 1-52 weeks were included in the final analysis. The mean [95% CI] effect size of change in pain ratings in the no-treatment control studies at outcome points up to 10 weeks was 0.18 [-0.05, 0.41] and for outcomes from 12-52 weeks it was 0.4 [0.12, 0.68]. In the placebo control groups it was 0.50 [0.10, 0.90] at up to 10 weeks and 0.33. [-1.97, 2.66] at 12-24 weeks. None of the comparisons between the no-treatment and placebo groups were statistically significant.
  
  
  CONCLUSIONS
  It appears that the changes in pain scores in subjects with chronic neck pain not due to whiplash who are enrolled in no-treatment and placebo control groups were similarly small and not significantly different. As well, they do not appear to increase over longer-term follow-up.
authors.affiliation: Department of Graduate Education and Research, Canadian Memorial Chiropractic College, Toronto, Ontario, Canada. hvernon@cmcc.ca
authors.forename: Howard
authors.initials: H
authors.lastname: Vernon
authors.forename: B Kim
authors.initials: BK
authors.lastname: Humphreys
authors.forename: Carol
authors.initials: C
authors.lastname: Hagino
mesh_terms: D002908:Chronic Disease; D006801:Humans; D019547:Neck Pain / Q000628:therapy*; D016032:Randomized Controlled Trials as Topic; D016896:Treatment Outcome