Individuals' expectations on returning to work after an injury have been shown to predict the duration of time that a person with work-related low back pain will remain on benefits; individuals with lower recovery expectations received benefits for a longer time than those with higher expectations. The role of expectations in recovery from traumatic neck pain, in particular whiplash-associated disorders (WAD), has not been assessed to date to our knowledge. The aim of this study was to investigate if expectations for recovery are a prognostic factor after experiencing a WAD.
Methods and Findings
We used a prospective cohort study composed of insurance claimants in Sweden. The participants were car occupants who filed a neck injury claim (i.e., for WAD) to one of two insurance companies between 15 January 2004 and 12 January 2005 (n = 1,032). Postal questionnaires were completed shortly (average 23 d) after the collision and then again 6 mo later. Expectations for recovery were measured with a numerical rating scale (NRS) at baseline, where 0 corresponds to “unlikely to make a full recovery” and 10 to “very likely to make a full recovery.” The scale was reverse coded and trichotomised into NRS 0, 1–4, and 5–10. The main outcome measure was self-perceived disability at 6 mo postinjury, measured with the Pain Disability Index, and categorised into no/low, moderate, and high disability. Multivariable polytomous logistic regression was used for the analysis. There was a dose response relationship between recovery expectations and disability. After controlling for severity of physical and mental symptoms, individuals who stated that they were less likely to make a full recovery (NRS 5–10), were more likely to have a high disability compared to individuals who stated that they were very likely to make a full recovery (odds ratio [OR] 4.2 [95% confidence interval (CI) 2.1 to 8.5]. For the intermediate category (NRS 1–4), the OR was 2.1 (95% CI 1.2 to 3.2). Associations between expectations and disability were also found among individuals with moderate disability.
Citation: Holm LW, Carroll LJ, Cassidy JD, Skillgate E, Ahlbom A (2008) Expectations for Recovery Important in the Prognosis of Whiplash Injuries. PLoS Med 5(5): e105. doi:10.1371/journal.pmed.0050105
Academic Editor: Andrew Rice, Imperial College London, United Kingdom
Received: June 18, 2007; Accepted: March 27, 2008; Published: May 13, 2008
Copyright: © 2008 Holm et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The work was funded by grants from the Swedish Council for Working Life and Social Research, from Volvo Safety Centre, Gothenburg, from the Swedish Society for Insurance Medicine, and from the Söderström-Königska Nursing Home Foundation. Linda Carroll is supported by a Health Scholar award from the Alberta Heritage Foundation for Medical Research. The funding agencies had no role in the study design, data collection and analysis, or decision to publish the manuscript.
Competing interests: All authors declare that they have no conflict of interest in connection with this paper. Lena Holm is employed part-time at a Swedish insurance company (Trygg-Hansa), and is also a part-time researcher at the Karolinska Institutet. Linda Carroll and David Cassidy received research grants from governmental insurance sources outside of Sweden. Two Swedish insurers, Trygg-Hansa and Aktsam) provided computer-based personal information on eligible participants for the present study, but otherwise did not have any role in data collection, the objectives of the study, the analysis or the interpretation of the data.
Abbreviations: HADS, Hospital Anxiety and Depression Scale; IES, Impact of Event Scale; NRS, numerical rating scale; OR, odds ratio; PDI, Pain Disability Index; WAD, whiplash-associated disorders
The disability associated with injury is a major source of distress for patients, and can be costly to the health care system and employers when persons fail to recover quickly and are unable to return to work. Finding ways to help people recover quickly and get back to optimal health is important. Some of the most common injuries causing disability and time off work result from whiplash—the sudden hyperextension or “whipping” of the neck, which can occur from a motor vehicle crash. It has long been recognized that psychological factors (such as the ability to cope, how “in control” one feels about one's life) are as important as physical symptoms in how disabling an injury can be. There is now growing evidence that a person's feelings about their ability to recover from injury plays a part in actual recovery. Studies from Europe and North America have shown with conditions like low back pain and minor head injury that a patient's feelings about the possibility of getting better are related to how well they do. Less is known about how important these psychological factors are in recovery from disorders due to whiplash associated disorders.
Why Was This Study Done?
The authors wanted to find out whether there was a relationship between people's expectations for their recovery from whiplash associated disorders and their actual recovery six months later. So, for example, they wondered if a person with whiplash who felt they were very unlikely to recover from their injury, actually did not recover (and vice versa).
What Did the Researchers Do and Find?
The authors had access to an unusual set of health information—insurance claims by people who had been involved in car collisions to two insurance companies in Sweden. They identified about 1,000 adult insurance claimants over one year and mailed them a questionnaire that asked for details about the collision as well as information about the claimant: their demographic profile, health history, and the types of pain and symptoms experienced since the crash. The questionnaire also asked the claimant how likely they thought they were to make a full recovery from their injuries.
For those who said they had whiplash associated disorders, the authors followed up with another questionnaire six months later, which asked for information about any disability, pain, or other symptoms that the claimant was still experiencing because of the injury. Of those who had completed the first questionnaire, 82% were followed up.
Only about a quarter of claimants with whiplash associated disorders said they expected to make a full recovery. Perhaps not surprisingly, those with only mild pain, compared to those with intense pain, were more likely to think so. Persons who said they were less likely to make a full recovery were four times more likely to report high levels of disability six months later. Even for persons (or individuals) people with moderate levels of disability six months after injury, their expectations for recovery were similarly linked to how well they did: the lower the expectations for recovery, the higher the disability. These findings were true even after taking into account how severe signs and symptoms the person had, and how well the person was coping psychologically.
What Do These Findings Mean?
The findings indicate that those with the lowest expectations for recovery after their whiplash injury will have the poorest recovery, and those with the highest expectations will have the best recovery. They also suggest that a patient's expectations about getting better are as important as his or her physical symptoms. The authors say that the more we can influence patients to believe they will make a full recovery, the better chance they will have to recover completely. This means that it may be beneficial for healthcare providers to give support and/or education to patients with whiplash associated disorders that increases their positive feelings toward recovery. The authors call for more studies into whether these types of targeted interventions would be of benefit.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050105.
- Information about research on injuries and rehabilitation can be found at the Web sites of organisations devoted to studying the health of workers, such as the Institute for Work and Health in Canada, the Finnish Institute of Occupational Health, and the US National Institute for Occupational Safety and Health
- The Wikipedia entry for medical aspects of whiplash describes the four grades of whiplash disorder, but does not cover the debate about the credibility of whiplash disorder (please note that Wikipedia is an online encyclopedia that anyone can edit)
- The Sjukvardsradgivningen Web site provides information about whiplash-related disorders, common signs and symptoms, recovery and prognosis, and treatments (in Swedish)
Whiplash is an acceleration-deceleration mechanism resulting from an energy transfer to the neck that may lead to a variety of clinical manifestations (whiplash-associated disorders [WAD]) . Despite substantial research over many years, understanding prognostic factors for WAD recovery is sparse [1,2]. High pain intensity in the neck and head, radicular signs/symptoms, older age, female gender, and tort insurance systems are associated with delayed recovery . Psychological and psychosocial factors such as general psychological distress , early depressive symptoms , passive coping strategies , perceived helplessness , and higher levels of somatisation  are also associated with poor prognosis in WAD. Several studies also indicate a substantial difference in recovery between countries [2,8]. Such variation might reflect differences across study populations, different inclusion criteria, or different health-care seeking behaviour, but might also reflect societal and individual differences in the perception or expectations of the injury and for recovery. Thus expectations might in turn influence prognosis. Results from studies of uninjured individuals' perceptions of the symptoms that may arise from WAD and those from mild traumatic head injuries suggest that there are differences between countries in the perceptions of presence and duration of symptoms. For example in Lithuania and Greece, symptoms are expected to be fewer and to be present for a shorter duration than is the case in Canada [9,10].
The concept of expectations for recovery is complex. Janzen et al. have suggested a conceptual model for health expectations, which can also be applied to recovery expectations . Such expectations are, apart from the symptoms/signs of the disease or injury, influenced by prior health and prior knowledge of the condition, as well as by psychological characteristics such as anxiety, self efficacy, and the patient's beliefs. Systematic reviews of research on various clinical conditions and outcomes have concluded that expectations contribute to the patients' outcome, including recovery duration and return to work [12,13].
Over the past 10–15 y, considerable attention has been given to WAD in the Swedish media. WAD are often considered to have severe consequences. Such “prior knowledge” might have an impact on expectations of the prognosis for individuals experiencing WAD. To our knowledge, the role of recovery expectations in individuals with traumatic pain has not been studied. Therefore, the objective of this study was to assess the prognostic value of individuals' expectations for recovery after WAD.
A cohort was formed from incident cases of injury claimants to two Swedish traffic insurers: Trygg-Hansa and Aktsam. The inception period was between January 15, 2004 and January 12, 2005. A weekly computer-based search of new claims was performed at the insurer's information technology department. The following criteria were used for the search: claimant age 18–74 y; car occupants who filed an injury claim within 30 d of a collision; and no fatal injury to another occupant in the same car. Identifying information on each injured person was transferred to Karolinska Institutet (KI) on a weekly basis. The following day, questionnaires were sent from our research centre at KI . The questionnaire included questions concerning the collision, socioeconomic and preinjury health status, and pain and other symptoms experienced since the collision. We included questions assessing mental health and questions that could capture information about the injured person's expectations for a complete recovery. Because of a risk of low or delayed response during the summer holiday of 2004, claims made during 16 June and 3 August 2004 were excluded. At 6 mo postinjury, a follow-up questionnaire was administered to those who responded to the baseline questionnaire. Here we asked about the disability and signs and symptoms that the participants attributed to the injury 6 mo earlier. At 6 mo after the last inception into the study, we also retrieved information from the insurers on all claimants about whether they had completed their claim, and whether the claim was settled or not.
We included claimants who met the criteria outlined above, and who (i) reported WAD (defined below), (ii) were not hospitalized for more than 2 d, and (iii) did not have other injury claims reported during the inception period. We excluded those who were not Swedish residents, those with complete recovery at baseline, those who had missing data on expectations for recovery, and those who, at follow up, reported that they had experienced any new injury during the past 6 mo. The study was approved by the Regional Committee on Ethics at Karolinska Institutet, Stockholm.
Definition of WAD
WAD was defined as having answered “yes” to any of the following questions in the questionnaire: “Do you have or have you had pain/ache in the neck due to the accident?” or “Do you have or have you had reduced neck movement that you relate to the accident?” Cervical fractures were excluded.
Disability was assessed with the seven-item Pain Disability Index (PDI) questionnaire, which ranges from 0 to 70, where 0 is no disability due to pain . PDI was trichotomised with cut-off scores at the median and at the 75th percentile.
Expectations for recovery were measured with a numerical rating scale (NRS 0–10) where the respondents were asked to rate how likely it was that he/she would have a complete recovery. The anchors were labeled “not likely” (0) and “very likely” (10). For the analysis, we reversed the scale and arbitrarily trichotomised it into those who stated that they were less likely to make a full recovery (NRS 5–10), an intermediate category (NRS 1–4), and those who stated that they were very likely to make a full recovery (NRS 0).
We used the baseline information when choosing potential confounders. The choice was guided by knowledge of prognostic factors for neck pain and WAD (Box 1). Postcollision symptoms were (i) pain referring to three specified anatomic regions and one option for “other” region, all assessed with numerical rating scales (NRS 0–10); (ii) number of pain areas from pain drawings ; and (iii) mental health, using the Hospital Anxiety and Depression Scale (HADS) [16,17]. We assessed psychological stress after the collision with the Impact of Event Scale (IES) [18,19]. In the analysis of potential confounders, HADS subscales and IES were all treated both as categorical variables according to suggested cut-off scores [16,20] and as continuous variables.
Box 1. Factors Considered as Potential Confounders in the Relation between Expectations of Recovery and Subsequent Disability
Number of days between injury and completion of the baseline questionnaire
General health prior to injury including prior neck pain and headache
Memory loss after the injury
Number of pain areas
Severity of eight pain-associated symptoms
Pain intensity in the neck, head, low back and other body parts
Anxiety and depression
Posttraumatic stress symptoms
Passive coping strategies
Moreover, we used a subscale of the Pain Management Inventory to assess passive coping [21,22]. The presence and severity of eight pain-associated symptoms were assessed with a checklist, with a five-grade verbal scale ranging from “no symptoms” to “unbearable symptoms.”
We used multivariable polytomous logistic regression . We first assessed the crude associations between the exposure and pain disability. The exposure was treated both as a continuous and categorical variable, thus we built two different regression models. We determined the role of confounders by considering each potential confounder in turn in the models . If any single variable changed any of the crude estimates by more than 10%, they were entered in the final model . We also evaluated the final full model by removing one confounder at a time. We tested for the presence of interaction by stratifying for gender, educational level, and level of pain intensity. Results are presented as crude and adjusted odds ratios (ORs) with 95% confidence intervals (CIs).
Responders were compared with nonresponders, to determine potential bias as a result of selective participation. We had information on all claimants regarding age, gender, and whether they had completed the injury claim or not. We also compared those with WAD who responded to the baseline questionnaire with those who were successfully followed for 6 mo.
All statistical analyses were performed with the use of SPSS software package version 14.0 .
Between January 15, 2004 and January 12, 2005, there were 4,603 eligible claimants fulfilling the search criteria at the insurance companies. Of these, 676 were filed during the summer of 2004, and were excluded. Another 52 had an unknown address, were not car occupants, or were not Swedish residents. Of the remaining claimants 3,875 were successfully approached with questionnaires. Figure 1 illustrates the inclusion and exclusions of study participants, as well as the attrition from the study.
*Returned questionnaires; † WAD, whiplash-associated disorders.
Compared to the responders, the nonresponders were younger (mean age 37.2 y versus 39.3 y), had a lower proportion of females (43.9% versus 56.1%), and a higher proportion of uncompleted claims (40.7% versus 17.7%). There were no essential differences between the WAD claimants who completed both questionnaires compared to those who completed only the baseline questionnaire with respect to sociodemographic characteristics, recovery expectations, physical and mental symptoms at baseline, and proportion of settled claims.
The baseline questionnaire was completed on average 23 d (median 20 d) postinjury, with 4% responding within 7 d and 81% within 30 d of the collision. Table 1 presents a description of the 1,032 persons in the study population. Table 2 shows the proportion of the three categories of expectations stratified by baseline neck pain intensity and disability. In all 278 persons (27%) in both pain strata rated themselves to be very likely to make a full recovery. As expected, those with mild pain intensity were more likely to expect complete recovery compared to persons with intense pain, but 123 (17%) of those in the mild pain strata were pessimistic about their recovery. On the contrary, only 22 (7%) in the moderate/severe pain group had rated it very likely to have complete recovery, and 160 (50%) fell into the lower group of expectations.
Baseline Characteristics of the Study Population (n = 1,032)
Recovery Expectations and Disability
The crude ORs of the associations between expectations for recovery and pain disability are presented in Table 3. It also shows the crude OR for demographic and prior health factors, and for the confounding factors. After adjustment for confounders, the odds of high disability in individuals who stated they were less likely to make a full recovery were 4.2 times the odds in individuals who stated they were very likely to make a full recovery (Table 3). There was a dose response relationship, in that the intermediate category (NRS 1–4) was also associated with severity of disability, but the ORs were smaller. These estimates were independent of whether we modelled the confounders; anxiety, depression, and posttraumatic stress as category variables or as continuous variables. When stratifying the data by mild (NRS 0–4) versus moderate/severe (NRS 5–10) baseline neck pain, we found a stronger effect in the mild neck pain strata. However, there were only 22 individuals in the joint category of “moderate/high neck pain intensity” and stating “very likely to recover,” which precluded a formal interaction analysis (Table 2).
Expectations for recovery were an important factor in the prognosis of WAD, for both moderate and high disability, with a clear dose response relationship. To our knowledge this is the first study to assess these associations in WAD. The significance of the findings is that in addition to an understanding of the injury and its clinical symptoms, the patient's perception of recovery is necessary information for a proper understanding of WAD. Only 27% of the study participants reported that they were very likely to make a complete recovery. Interventions with the goal of changing expectations and beliefs may therefore benefit a large proportion of individuals with WAD.
The study's strengths include the prospective design with a well-defined study population and assessment of recovery expectations early after the injury. Moreover the study is based on a well-defined population of injured persons, in which a variety of potential confounders were evaluated. We tested the robustness of the regression models both in single and combined ways, and the findings were broadly similar regardless of which statistical modelling strategy was used.
Our study has some limitations. Nonparticipants were more likely to be younger and male. However, this would have an impact on the results only if these factors were confounders in the relation between expectations of recovery and disability. The nonparticipants were also less likely to have completed their claim. Since all persons, irrespective of whether or not they are responsible for the collision, are entitled to insurance compensation in Sweden, we assume that nonparticipants were less likely to have sustained an injury or only a transient injury. Although residual confounding is possible because of misclassified or unmeasured confounders, the strength of the associations observed for high disability make it unlikely that the findings can be fully explained by residual confounding. However, it is possible that passive coping strategies, anxiety, depressive symptomatology, and other similar psychological characteristics influence the perception of disability in other ways than by being confounders. Some factors might act as mediators, or for some factors the causal change might be reversed. For instance recovery expectations might effect how individuals report intensity of pain, instead of pain intensity effecting expectations for recovery. Thus, we cannot be confident that there is a causal relationship between recovery expectations and actual recovery. Nevertheless, other studies have found that early positive information about the injury, which is one way of modifying recovery expectations, has a favourable impact on the prognosis [26,27]. In a recent intervention study in which the authors investigated the efficacy of informational group sessions for high risk patients with mild injuries after traffic collisions (including WAD), the intervention group had a 20% greater recovery rate compared to the group who received “general care” . In that study expectations for recovery were not measured, but one possible explanation for the positive effect in the intervention group, may be that the expectations for recovery were modified by the group sessions. Previous findings from studies on conditions similar to WAD also suggest that individuals' expectations are important factors in recovery and return to work [12,29,30]. The fact that we found a dose response relationship between level of expectations and the level of reported disability is a further indication of a causal relationship. If future interventional studies show that modifying expectations of recovery reduced or removed this association, it would be a further step towards demonstrating causality.
The substantial influence of initial expectations on subsequent disability, even after considering the impact of baseline pain intensity and other symptoms, might be a partial explanation for anecdotal reports of long term dysfunction in persons with initially mild WAD symptoms.
In conclusion, we suggest early assessment of expectations for recovery to be made, in order to identify people at risk for poor prognosis after WAD. Furthermore, controlled studies on interventions aimed at modifying expectations are warranted. Such studies could be conducted on the population level, similar to the successful media campaign on back pain beliefs, which decreased disability claims, both in terms of incidence and time on benefits [31,32]. Alternatively interventions targeting persons in the acute phase of an injury should be evaluated. Finally, it is not inconceivable that our findings can be extended to persons with pain conditions other than WAD.
Alternative Language Abstract S1. Translation of Abstract into Swedish by LH
(40 KB DOC)
We would like to acknowledge the presidents of the claims' departments at Trygg-Hansa and Aktsam for providing access to their claims' databases. We would also like to thank the programmers in the information technology department for providing claimant information.
LWH and AA designed the experiments/the study. LWH and AA analyzed the data. LWH enrolled patients. LWH wrote the first draft of the paper. LJC, JDC, ES, and AA contributed to writing the paper. LJC contributed to the development of the design and methodology of the study and provided consultation/advice about the analysis.
- 1. Spitzer W, Skovron M, Salmi L, Cassidy J, Duranceau J, et al. (1995) Scientific monograph of the Quebec Task Force on whiplash-associated disorders: redefining “whiplash” and its management. Spine 15: 1S–73S.
- 2. Côté P, Cassidy JD, Carroll L, Frank JW, Bombardier C (2001) A systematic review of the prognosis of acute whiplash and a new conceptual framework to synthesize the literature. Spine 26: E445–E458.
- 3. Atherton K, Wiles NJ, Lecky FE, Hawes SJ, Silman AJ, et al. (2006) Predictors of persistent neck pain after whiplash injury. Emerg Med J 23: 195–201.
- 4. Carroll LJ, Cassidy JD, Cote P (2006) Frequency, timing, and course of depressive symptomatology after whiplash. Spine 31: E551–E556.
- 5. Carroll LJ, Cassidy JD, Cote P (2006) The role of pain coping strategies in prognosis after whiplash injury: passive coping predicts slowed recovery. Pain. pp. 18–26.
- 6. Berglund A, Bodin L, Jensen I, Wiklund A, Alfredsson L (2006) The influence of prognostic factors on neck pain intensity, disability, anxiety and depression over a 2-year period in subjects with acute whiplash injury. Pain 125: 244–256.
- 7. Hendriks EJ, Scholten-Peeters GG, van der Windt DA, Neeleman-van der Steen CW, Oostendorp RA, et al. (2005) Prognostic factors for poor recovery in acute whiplash patients. Pain 114: 408–416.
- 8. Miettinen T, Airaksinen O, Lindgren KA, Leino E (2004) Whiplash injuries in Finland–the possibility of some sociodemographic and psychosocial factors to predict the outcome after one year. Disabil Rehabil 26: 1367–1372.
- 9. Ferrari R, Obelieniene D, Russell A, Darlington P, Gervais R, et al. (2002) Laypersons' expectation of the sequelae of whiplash injury. A cross-cultural comparative study between Canada and Lithuania. Med Sci Monit 8: 728–734.
- 10. Ferrari R, Constantoyannis C, Papadakis N (2001) Cross-cultural study of symptom expectation following minor head injury in Canada and Greece. Clin Neurol Neurosurg 103: 254–259.
- 11. Janzen JA, Silvius J, Jacobs S, Slaughter S, Dalziel W, et al. (2006) What is a health expectation? Developing a pragmatic conceptual model from psychological theory. Health Expect 9: 37–48.
- 12. Mondloch M, Cole D, Frank J (2001) Does how you do depend on how you think you'll do? A systematic review of the evidence for a relation between patients' recovery expectations and health outcomes. CMAJ 165: 174–179.
- 13. Kuijer W, Groothoff JW, Brouwer S, Geertzen JH, Dijkstra PU (2006) Prediction of sickness absence in patients with chronic low back pain: a systematic review. J Occup Rehabil 16: 430–458.
- 14. Tait RC, Pollard CA, Margolis RB, Duckro PN, Krause SJ (1987) The Pain Disability Index: psychometric and validity data. Arch Phys Med Rehabil 68: 438–441.
- 15. Margolis R, Tait R, Krause S (1986) A rating system for use with patient pain drawing. Pain 24: 57–65.
- 16. Zigmond AS, Snaith RP (1983) The hospital anxiety and depression scale. Acta Psychiatr Scand 67: 361–370.
- 17. Bjelland I, Dahl AA, Haug TT, Neckelmann D (2002) The validity of the Hospital Anxiety and Depression Scale. An updated literature review. J Psychosom Res 52: 69–77.
- 18. Horowitz M, Wilner N, Alvarez W (1979) Impact of Event Scale: a measure of subjective stress. Psychosom Med 41: 209–218.
- 19. Sundin EC, Horowitz MJ (2003) Horowitz's Impact of Event Scale evaluation of 20 years of use. Psychosom Med 65: 870–876.
- 20. Swinburne Centre for Neuropsychology, Swinburne University, Australia (2005) Impact of Event Scale. Available: http://www.swin.edu.au/victims/resources/assessment/ptsd/ies.html. Accessed 8 April 2008.
- 21. Brown GK, Nicassio PM (1987) Development of a questionnaire for the assessment of active and passive coping strategies in chronic pain patients. Pain 31: 53–64.
- 22. Snow-Turek AL, Norris MP, Tan G (1996) Active and passive coping strategies in chronic pain patients. Pain 64: 455–462.
- 23. Hosmer D, Lemeshow S (1989) Applied logistic regression. New York: John Wiley & Sons.
- 24. Rothman K (2002) Epidemiology: an introduction. New York: Oxford University Press Inc.
- 25. SPSS (2006) SPSS 14.0 for Windows. Chicago: SPSS.
- 26. Peeters GG, Verhagen AP, de Bie RA, Oostendorp RA (2001) The efficacy of conservative treatment in patients with whiplash injury: a systematic review of clinical trials. Spine 26: E64–E73.
- 27. Oliveira A, Gevirtz R, Hubbard D (2006) A psycho-educational video used in the emergency department provides effective treatment for whiplash injuries. Spine 31: 1652–1657.
- 28. Ottosson C, Pettersson H, Johansson SE, Nyren O, Ponzer S (2007) Recovery after minor traffic injuries: a randomized controlled trial. PLoS Clin Trials 2: e14. doi:10.1371/journal.pctr.0020014.
- 29. Cole D, Mondloch M, Hogg-Johnson S (2002) Listening to injured workers: how recovery expectations predict outcomes - a prospective study. CMAJ 166: 749–754.
- 30. Heymans MW, de Vet HC, Knol DL, Bongers PM, Koes BW, et al. (2006) Workers' beliefs and expectations affect return to work over 12 months. J Occup Rehabil 16: 685–695.
- 31. Buchbinder R, Jolley D, Wyatt M (2001) 2001 Volvo Award Winner in Clinical Studies: effects of a media campaign on back pain beliefs and its potential influence on management of low back pain in general practice. Spine 26: 2535–2542.
- 32. Buchbinder R, Jolley D (2005) Effects of a media campaign on back beliefs is sustained 3 years after its cessation. Spine 30: 1323–1330.