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University of Groningen

The course of whiplashBuitenhuis, Jan

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Relationship between post-traumatic stress disorder symptoms and the course of whiplash complaints

J. Buitenhuis, P.J. de Jong, J.P.C. Jaspers J.W. Groothoff

Published in: Journal of Psychosomatic Research 2006; 61:681– 689

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Abstract

Objective: This study investigates the relationship between post-traumatic stress disorder symptoms (avoidance, re-experiencing, and hyperarousal) and the presence, severity, and duration of neck complaints after motor vehicle accidents.

Methods: Individuals who had been involved in traffic accidents and had initiated compensation claim procedures with a Dutch insurance company were sent questionnaires (Q1) containing complaint-related questions and the Self-Rating Scale for post-traumatic stress disorder (SRS-PTSD). Of the 997 questionnaires that were dispatched, 617 (62%) were returned. Only car accident victims were included in this study (n=240). Complaints were monitored using additional questionnaires that were administered six (Q2) and twelve months (Q3) after the accident.

Results: Post-traumatic stress disorder was related to the presence and severity of concurrent post-whiplash syndrome. More specifically, the intensity of hyperarousal symptoms that were related to post-traumatic stress disorder at Q1 was found to have predictive validity for the persistence and severity of post-whiplash syndrome at six and twelve months follow-up.

Conclusion: Results are consistent with the idea that post-traumatic stress disorder hyperarousal symptoms have a detrimental influence on the recovery and severity of whiplash complaints following car accidents.

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Introduction

Whiplash is one of the most prevalent post-traumatic diagnoses following traffic accidents. The term whiplash refers to the presumed movement of the neck during an accident. The distortion of the neck that can follow from such movement usually declines over subsequent days or weeks. Even in the absence of identifiable structural injuries, victims may suffer from long-lasting complaints that are characterized by persistent neck pain, often accompanied by cognitive complaints. This persistent syndrome is usually known as whiplash associated disorder (WAD) or post-whiplash syndrome. Studies on the etiology of this chronic syndrome have led to conflicting opinions regarding the nature of the complaints, and the relevance of psychological factors.1-3

Although the majority of victims show spontaneous recovery within the first months after the traffic accident, as many as forty percent of the victims suffer from long-lasting symptoms, sometimes with severely disabling effects.4 Insight into factors that are responsible for this chronic course is therefore of great importance. The determination of such predictive factors may provide clues for effective interventions, in addition to its utility in the context of prevention.Several prognostic factors have already been identified by earlier research.5

First, it has been found that high initial pain intensity, female gender, and increasing age are predictive of delayed recovery.3,4,6 In addition, studies have shown that individual coping style may be involved in the course of whiplash complaints. More specifically, a palliative coping style has proven predictive of a chronic course.3,6

The presence of post-traumatic stress symptoms is another factor that may play an important role in the persistence of whiplash symptoms following a motor vehicle accident.7

Post-whiplash syndrome and post-traumatic stress disorder (PTSD) are both relatively common conditions following traffic accidents.8-11 As many as twenty-three percent of traffic accident victims are reported to have developed PTSD, which is known to have high psychiatric and medical co-morbidity.12-15

The symptoms of PTSD may be involved in the development of post whiplash-syndrome in several ways.

First, anxiety is an important feature of most PTSD symptoms. Because anxiety is known to influence the perception and experience of pain, PTSD symptoms may alter the perception and experience of acute neck pain.16 Inflated pain levels may subsequently fuel (avoidance) behaviors that facilitate a chronic course.17-19

Second, PTSD symptoms may result in heightened vigilance, which may inflate the

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perception of pain.20

Third, PTSD symptoms may give rise to a dysfunctional (catastrophic) interpretation of acute neck pain, which may subsequently inflate pain intensity, disability, and psychological distress, independent of the level of the actual physical impairment.21

Finally, PTSD shares several symptoms with acute whiplash syndrome, including insomnia, irritability, and cognitive problems. These symptoms may further intensify the perception of symptoms or lead to misattribution.

In support of the idea that the presence of PTSD symptoms affects the symptomatology of whiplash, earlier research has provided preliminary evidence to indicate that the acute post-traumatic stress response (i.e., re-experiencing and avoidance symptoms) are related to the intensity of whiplash symptoms four weeks after the accident.22

In addition, the results of a recent study have provided further evidence that PTSD symptoms may also influence the course of whiplash symptoms. More specifically, the study revealed the re-experiencing and avoidance subscales of the Impact of Events Scale to be associated with relatively persistent whiplash complaints at six months follow-up.23,24

Unfortunately, both previous studies tested only two of the three PTSD symptom scales and neither included the hyperarousal symptom cluster scale. Nonetheless, these symptoms may be highly relevant to the proper understanding of the relationship between PTSD and whiplash complaints.7

A study by Mayou and Bryant did consider all three post-traumatic stress disorder symptoms scales. The participants that they recruited, however, included only victims who had visited an emergency room following their accidents, thereby possibly biasing the results toward patients who were more frightened or whose injuries were more serious.25

The present study was therefore designed to provide further testing of the robustness and validity of these earlier findings, which suggest that PTSD symptoms are related to the intensity of whiplash complaints and that they have predictive validity regarding recovery from whiplash complaints following motor vehicle accidents. This study includes the hyperarousal symptom cluster in addition to re-experiencing and avoidance symptoms

To test for generalizability, we did not restrict the range of victims to emergency-room visitors. Finally, we examined whether the relationship between PTSD symptoms and whiplash complaints had increased or decreased at prolonged (twelve-month) follow-up.

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More specifically, the present study addresses the following questions:

1. Are PTSD symptoms more frequent among individuals who have post-whiplash syndrome?

2. Are PTSD symptoms related to the severity of whiplash complaints?3. Is the presence of PTSD symptoms predictive of delayed recovery from post-whiplash

syndrome?

Methods

Study designWe used a prospective longitudinal design. Participants were assessed at one (Q1),

six (Q2), and twelve months (Q3) after their accidents.

Participants and procedureTraffic-accident victims who had initiated compensation claim procedures for

personal injury with a Dutch insurance company were asked to participate in this study. In the Netherlands, settlement of personal injury claims is based on liability insurance; accident victims seek compensation from the insurance company of the driver who was at fault. The letter of invitation clearly communicated that the present study was independent of the compensation procedure.

During the intake period, 997 questionnaires were dispatched. Questionnaires were not sent to claimants who were known to be younger than 18 or older than 65 years of age. The median time for dispatching the questionnaire was 21 days after the accident (mean 22.15 days, SD=11.197). The number of initial questionnaires that was returned was 617 (62%).

The initial selection from the returned questionnaires included only the responses of victims who had been in car accidents (n=293). To rule out the potentially confounding influence of concurrent complaints and to obtain a homogeneous sample of participants with only soft-tissue injuries, 30 victims were excluded because of a history of whiplash or neck pain, 15 because of one or more fractures, and 8 because of the absence of physical complaints. In the final sample, therefore, the responses of 240 participants were eligible for further analysis.

Questionnaires and outcome variablesAfter a median time of 21 days after the accident, we sent each claimant a questionnaire

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(Q1) concerning the accident, the injuries that they had sustained, and their complaints at that time. Table 1 provides an overview of the questionnaire items.

Table 1. Overview of variables analyzed

Variable values

Age yearsGender male, femaleLoss of consciousness no, for a moment, <1 minute, <10 and >10 minutesHospital visit no; immediately by ambulance; immediately, on own initiative; later, after visit to GPHospital admittance no, < 1 day, >1 dayGeneral practitioner visit no, <1 day, <1 week, >1 weekBack-pain intensity 1 (no pain) – 10 (severe pain)Neck-pain intensity* 1 (no pain) – 10 (severe pain)Headache intensity* 1 (no pain) – 10 (severe pain)Neck stiffness* 1 (no stiffness) – 10 (severe stiffness)Severity of neck-movement restriction* 1 (no restrictions) –10 (severe restriction)Radiating pain in arms* 1 (no) – 10 (severe pain)Severity of paresthesia in the arms* 1 (no) – 10 (severe paresthesia)Concentration complaints* 1 (no) to 10 (severe complaints)Difficulty reading* 1 (no) to 10 (severe complaints)Difficulty concentrating on a conversation* 1 (no) to 10 (severe complaints)Dizziness* 1 (no) to 10 (severe dizziness)Use of medication since accident no/yes (includes analgesics and/or muscle relaxants)Sleep disturbance no/yesFrequency of neck pain* Ŧ 1 (daily) to 4 (at least once a month)Onset of neck complaints hours after accidentPost-traumatic stress questionnaire (SRS-PTSD) Three scales

* Variable used in whiplash-severity scoreŦ Before analyses recalculated by using: 12 – (2 x original value))

Consistent with our previous studies on post-whiplash syndrome, claimants who suffered from neck pain, a loss of consciousness of no longer than one minute, and no self-reported previous neck complaints were included as post-whiplash syndrome patients3,6

The presence of post-traumatic stress disorder was assessed using the Self-Rating Scale for PTSD (SRS-PTSD).27 This questionnaire was designed as an abridged version of the Structured Interview for Post-Traumatic Stress Disorder (SI-PTSD), which measures the presence and severity of post-traumatic stress disorder symptoms from both a current and

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a lifetime perspective28. The SRS-PTSD consists of questions that assess the three major symptom groups of post-traumatic stress disorder, as listed in the DSM-IV. Eight questions assess the five re-experiencing symptoms; ten questions assess the seven avoidance symptoms, and six questions assess the five hyperarousal symptoms. In accordance with the DSM-IV criteria for PSTD, participants were considered as suffering from PTSD if they reported at least one re-experience, three avoidance symptoms, and two hyperarousal symptoms.29

We monitored the course of complaints, in all participants, regardless of the presence of initial complaints, at six (Q2) and twelve (Q3) months after the accident by means of the Self-Rating Scale for PTSD (SRS-PTSD). In addition, two identical questionnaires containing questions regarding the complaints at that moment in time were completed.

Data reductionPTSD symptoms

A dichotomous variable was computed for each assessment point to indicate whether the diagnostic requirements for post-traumatic stress disorder were met. In addition to this dichotomous variable, the actual number of avoidance, re-experiencing, and hyperarousal symptoms were used as independent variables.

Whiplash complaintsA severity score was calculated as the sum of the eleven complaint variables that

are marked in Table 1 for each individual who was suffering from post-whiplash syndrome at each of the three assessment points. The reliability of these indices in terms of internal consistency was satisfactory. (Q1: Cronbach’s alpha=0.88, n=134; mean=52.9, sd=20.2, Q2: Cronbach’s alpha=0.89, n=79; mean=53.5, sd=20.5, Q3: Cronbach’s alpha=0.91, n=62; mean=53.0, sd=20.2). In addition, a dichotomous variable was computed for each assessment point to indicate whether whiplash syndrome (i.e., persistent neck pain) was still present.

AnalysisCategorical variables were recoded into appropriate dummy variables before they

were used in the regression analyses. The independent variables used in the regression analyses were first analyzed in associated groups.

When analyzing the relationship between PTSD symptoms and the intensity of concurrent post whiplash-syndrome complaints (section 3.3), the groups consisted of: first group: hospital visit, hospital admission and visit GP. Second group: medication since accident, back-pain complaints and onset of neck complaints. Variables with significant

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properties were then simultaneously included in the final regression analysis, together with age, gender and the categorical PTSD variable or the PTSD symptoms..

When analyzing the relationship between Initial PTSD symptoms and the persistence and severity of post-whiplash syndrome at six and twelve months follow-up (section 3.4), the groups consisted of: first group: hospital visit, hospital admission and visit GP. Second group: back pain intensity, headache intensity, use of medications since accident, concentration, difficulty reading, difficulty concentrating on a conversation and dizziness. Third group: neck-pain intensity, frequency of neck-pain, onset of neck complaints, neck stiffness, severity of neck-movement restriction, radiating pain in arms and severity of paresthesia in the arms. Variables with significant properties were then simultaneously included in the final regression analysis, together with age, gender and the categorical PTSD variable or the PTSD symptoms.

Next, using a backward stepwise selection procedure, the least significant variables were removed (visit GP, headache intensity, back-pain intensity and, when analyzing the PTSD symptoms, dizziness), using the drop-in-deviance test to compare the new with the last model, while retaining age, gender, and the PTSD variable(s) in the model. The final models therefore contain age, gender, the PTSD variable(s), and significant confounders.

Results

General resultsTable 2 provides an overview of the basic characteristics of participants (n=240).

Of the 240 participants in the final sample, 32 (20 with post-whiplash syndrome on Q1) did not return the second questionnaire, and 18 (11 with post-whiplash syndrome on Q1) did not return the third questionnaire. Analysis indicated no significant differences between those who did and those who did not return the questionnaire with respect to their scores during the first assessment.

Table 2 provides an overview of the characteristics of both groups of participants (i.e., those with post-whiplash syndrome and those without) as well as descriptive variables on Q1. Using univariate logistic regression, the group of individuals with post-whiplash syndrome consisted of significantly more women than men. In addition, victims with post-whiplash syndrome had visited their general practitioners relatively frequently. None of the other variables showed significant differences between the groups.

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Table 2. Basic characteristics of the eligible group (n=240) at Q1, one month after the accident.

Post-whiplash syndrome no yes whole group

Number of participants 106 134 240 Age, mean (sd) 35.6 (13.4) 36.3 (12.3) 36.0 (12.8) Gender, male (%) * 48 (45.3) 39 (29.1) 87 (36.3)

Loss of consciousness no (%) 95 (89.6) 120 (89.6) 215 (89.6) for a moment (%) 8 (7.5) 14 (9.5) 22 (9.2) less than 1 minute (%) 0 4 (3.0) 4 (1.7) less than 10 minutes (%) 0 0 0 more than 10 minutes (%) 3 (2.8) 0 3 (1.3)

Hospital visit no (%) 62 (58.5) 70 (52.2) 132 (55.0) immediately, by ambulance (%) 32 (30.2) 38 (28.4) 70 (29.2) immediately, on own initiative(%) 7 (6.6) 13 (9.7) 20 (8.3) later, after a visit to general ) 5 (4.7) 13 (9.7) 18 (7.5) practitioner (%

Hospital admission no (%) 96 (90.6) 123 (91.8) 219 (91.3) yes, 1 day or shorter (%) 7 (6.6) 8 (6.0) 15 (6.3) yes, more than 1 day 3 (2.8) 3 (2.2) 6 (2.5)

Visit to general practitioner ** no (%) 48 (45.3) 20 (14.9) 68 (28.3) yes, the same day (%) 19 (17.9) 27 (20.1) 46 (19.2) yes, within one week (%) 31 (29.2) 71 (53.0) 102 (42.5) yes, after more than one week (%) 8 (7.5) 16 (11.9) 24 (10.0)

Neck-pain intensityŦ - 6.5 (2.25)Neck-pain frequency*** Daily (%) - 116 (86.6) More then 3 hours per week (%) - 8 (6) At least once a week (%) - 9 (6.7) At least once a month (%) - 0 (0%)

*: univariate logistic regression, Odds-ratio=2.016, 95% CI=1.182-3.439)**: univariate logistic regression, reference category “no”, dummy variable (dv) 1: Odds-ratio=3.411 , 95% CI=1.555-7.479, dv 2: Odds-ratio=5.497, 95% CI=2.810-10.752, dv 3: Odds-ratio=4.800, 95% CI=1.773-12.998)***: one missing case Ŧ : Information on other variables available from the first author

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PTSD symptoms at one, six, and twelve monthsThe presence of PTSD and the mean number of symptoms for each symptom cluster

at each assessment point are shown in Table 3.

Table 3. Frequency of post-traumatic stress disorder and symptom scales at one, six and twelve months.

Assessment point Q1 (1) Q2 (6) Q3 (12) (Months after the accident)post-whiplash syndrome no yes no yes no yes

Number of participants 106 134 129 79 128 62

Post-traumatic stress disorder, yes (%) 4 22 4 20 5 11 (3.8) (16.4) (3.1) (25.3) (3.9) (17.7) Re-experiencing symptoms, mean (sd) 1.16 2.11 0.63 1.59 0.67 1.44 (1.442) (1.684) (1.125) (1.581) (1.102) (1.543) Avoidance symptoms, mean (sd) 0.66 1.38 0.50 1.80 0.45 1.77 (1.004) (1.381) (0.772) (1.409) (0.895) (1.311) Hyperarousal symptoms, mean (sd) 0.49 1.66 0.42 1.95 0.37 1.79 (0.928) (1.420) (0.826) (1.440) (0.752) (1.332)

At all assessment points (i.e., Q1, Q2 and Q3), PTSD was more prevalent in the group of victims with post-whiplash syndrome than it was among the participants who did not report these symptoms (Chi-square with Yates’ continuity correction, Χ2=8.53; df=1; p=0.003, Χ2=21.56; df=1; p<0.001 and Χ2=8.65; df=1; p=0.003, respectively).

For all assessments, the mean number of re-experiencing, avoidance, and hyperarousal symptoms was relatively high in the group with post-whiplash syndrome (t-test, t’s<-3.4, p’s<0.001). This pattern remained unaffected when the results were corrected for age and gender using analysis of covariance (F-values>13.73, p’s<0.001).

Of the twenty-six individuals who conformed to the diagnosis of post-traumatic stress disorder at Q1, five (19%) had not visited any doctor after the accident, eleven (42%) had been to a hospital immediately after the accident, and five (19%) had been admitted.

PTSD symptoms and the intensity of concurrent post whiplash-syndrome complaintsUsing the whiplash-severity score at the three assessment points as dependent

variables and all remaining variables from Table 1 as independent variables, linear regression analysis yielded the following results:

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The use of medication (beta=0.289, p<0.001), the severity of back pain (beta=0.275, p<0.001), and the presence of post-traumatic stress disorder at Q1 (beta=0.329, p<0.001) all were associated with the whiplash-severity score at Q1 (independent variables simultaneously included in the analysis: age, gender, back-pain intensity, use of medication, and categorical diagnosis of PTSD at Q1).

In a subsequent regression analysis, we substituted the number of PTSD symptoms for the three symptom clusters for the categorical diagnosis of PTSD (independent variables simultaneously included in the analysis: age, gender, back-pain intensity, use of medication, number of re-experiencing, avoidance, and hyperarousal symptoms). This analysis revealed that the number of post-traumatic avoidance (beta=0.303, p<0.001) and hyperarousal symptoms (beta=0.471, p<0.001) were statistically significantly associated with the concurrent whiplash-severity score at Q1, whereas the number of re-experiencing symptoms at Q1 (beta=-0.091, p=0.191) was not.

The use of medication (beta=0.247, p=0.03), the severity of back pain (beta=0.238, p=0.026), and the presence of post-traumatic stress disorder (beta=0.285, p=0.012) at Q2 were all associated with the concurrent whiplash-severity score.

In a subsequent regression analysis (independent variables simultaneously included in the analysis: age, gender, back-pain intensity, use of medication, number of re-experiencing, avoidance and hyperarousal symptoms), the number of avoidance symptoms (beta=0.308, p=0.028) six months after the accident were associated with the whiplash-severity score at Q2. The number of re-experiencing (beta=0.003, p=0.980) and hyperarousal symptoms (beta=0.242, p=0.088) at six months follow-up provided no statistically significant association with whiplash severity at Q2.

The use of medication (beta=0.267, p=0.031) at Q3 was associated with the concurrent whiplash severity. No statistically significant relationship was found with the presence of post-traumatic stress disorder at that assessment point (beta=0.205, p=0.102).

In a subsequent regression analysis (independent variables simultaneous included in the analysis: age, gender, back-pain intensity, use of medication, number of re-experiencing, avoidance and hyperarousal symptoms), the number of hyperarousal symptoms (beta=0.435, p=0.007) at Q3 were associated with the concurrent whiplash-severity score. The number of re-experiencing (beta=-0.026, p=0.869) and avoidance symptoms (beta=0.167, p=0.238) provided no significant association at Q3.

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Initial PTSD symptoms and the persistence and severity of post-whiplash syndrome at six and twelve months follow-up

Table 4 shows the results of two multiple logistic regression models after stepwise backward modeling, while retaining age, gender and the PTSD variable, using the presence of post-whiplash syndrome at Q2 and Q3 as the dependent variable and the variables from Q1 as independent variables. Most important for the present context, results indicated that the categorical presence of post-traumatic stress disorder at Q1 had no independent predictive value for the presence of post-whiplash syndrome at Q2 and Q3.

Table 4. Multiple Logistic Regression Model. Dependent variable post-whiplash syndrome at Q2 and Q3. Explanatory variables from Q1, including post-traumatic stress disorder.

Variable Coefficient Standard Wald P value Odds 95,0% C.I. (ß) Error Χ2 Ratio Lower Upper Post-whiplash syndrome at Q2

Constant -0.775 1.172 0.437 0.509 0.461 Gender -1.487 0.604 6.056 0.014 0.226 0.069 0.739Age -0.008 0.020 0.175 0.676 0.992 0.955 1.031PTSD 1.440 1.114 1.672 0.196 4.221 0.476 37.450Neck pain 0.353 0.126 7.801 0.005 1.423 1.111 1.822Dizziness 0.283 0.132 4.604 0.032 1.327 1.025 1.718

Post-whiplash syndrome at Q3

Constant -2.526 1.377 3.366 0.067 0.080 Gender -1.126 0.590 3.649 0.056 0.324 0.102 1.030Age 0.010 0.021 0.222 0.638 1.010 0.970 1.052PTSD 1.073 0.864 1.544 0.214 2.924 0.538 15.887Neck pain 0.416 0.141 8.726 0.003 1.516 1.150 1.998Dizziness 0.225 0.109 4.237 0.040 1.253 1.011 1.552

Since the inclusion of neck complaints in the equation may result in an underestimation of the actual strength of the association between PTSD and subsequent complaints (i.e., to the extent that neck pain lies in the causal pathway between PTSD and whiplash complaints), we performed an additional regression analysis in which we did not correct for neck pain at Q1. This additional regression analysis, with only age, gender and the categorical presence of post-traumatic stress disorder at Q1, revealed that the presence of PTSD at Q1 had an independent predictive value for the presence of post-whiplash syndrome at Q2 (Odds-ratio=13.941, 95% CI=1.757-110.600) and Q3 (Odds-ratio=7.518, 95% CI=1.583-35.718).

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In a subsequent analysis, we substituted the number of PTSD symptoms for the three symptoms clusters at Q1 for the categorical diagnosis of PTSD. Table 5 shows the results of the two models. With respect to the PTSD symptoms, only the number of hyperarousal symptoms at Q1 provided additional predictive value for the presence of subsequent post-whiplash syndrome at six and twelve months follow-up.

Table 5. Multiple Logistic Regression Model. Dependent variable post-whiplash syndrome at Q2 and Q3. Explanatory variables from Q1, including post-traumatic stress disorder symptoms.

Variable Coefficient Standard Wald P value Odds 95,0% C.I. (ß) Error Χ2 Ratio Lower Upper


Constant -0.820 1.227 0.447 0.504 0.440Gender -1.572 0.657 5.724 0.017 0.208 0.057 0.753Age -0.004 0.020 0.041 0.840 0.996 0.958 1.035Re-experiencing symptoms -0.268 0.194 1.898 0.168 0.765 0.523 1.120Avoidance symptoms 0.308 0.279 1.213 0.271 1.360 0.787 2.351Hyperarousal symptoms 0.686 0.289 5.633 0.018 1.985 1.127 3.497Neck pain 0.378 0.126 8.993 0.003 1.459 1.140 1.868


Constant -2.836 1.445 3.850 0.050 0.059Gender -1.076 0.619 3.025 0.082 0.341 0.101 1.146Age 0.018 0.021 0.678 0.410 1.018 0.976 1.062Re-experiencing symptoms -0.267 0.191 1.950 0.163 0.766 0.527 1.114Avoidance symptoms -0.012 0.259 0.002 0.963 0.988 0.595 1.641Hyperarousal symptoms 0.810 0.287 7.948 0.005 2.248 1.280 3.947Neck pain 0.438 0.138 10.072 0.002 1.549 1.182 2.031

Linear regression using the whiplash severity score as the dependent variable yielded similar results, showing hyperarousal symptoms at Q1 to be related to the severity of whiplash complaints at six (Q2) and twelve (Q3) months (beta=0.350, p=0.013, and beta=0.325, p=0.045 respectively). No relationship emerged between the number of re-experiencing and avoidance symptoms at Q1 and the whiplash-severity score at either Q2 or Q3.

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Discussion

The major results of the present study can be summarized as follows:Post-traumatic stress disorder and the number of its symptoms are more prevalent i. among car-accident victims who have post-whiplash syndrome than they are among victims who do not.The presence of post-traumatic stress disorder symptoms was associated with relatively ii. more severe concurrent post-whiplash syndrome complaints. Specifically, the initial number of hyperarousal symptoms was found to have predictive iii. validity for the persistence and severity of post-whiplash syndrome at six and twelve months follow-up.

In accordance with earlier research, post-traumatic stress disorder and its symptoms were found to be more prevalent among victims who had post-whiplash syndrome in the first six months following their accidents.22,23

Since earlier research has shown that the development of post-traumatic stress disorder is not substantially related to either the severity of the accident or the severity of the sustained injury, differences in the frequency of PTSD are not readily explained by any apparently terrifying aspect of the accident.30,31 The current results seem to correspond with earlier research that suggests that victims with post-whiplash syndrome generally considered the accident more frightening than did other car accident victims.25 Because perceived threat is of paramount importance in developing post-traumatic stress disorder, it could be speculated that the presence of whiplash complaints is threatening and induces anxiety complaints. This would make the accident more frightening and could subsequently lead to a relatively high number of post-traumatic stress complaints.

Previous research showing a relationship between post-whiplash syndrome and PTSD has relied predominantly on victims who were recruited in emergency rooms, thereby possibly biasing the results toward patients who were more frightened or whose injuries were relatively serious.25 In the present study, only a small minority of the car-accident victims who were included had actually visited a hospital following the accident. The present finding that the relationship between post-whiplash syndrome and PTSD can also be found in a broader sample underlines its generalizibility and indicates that this relationship reflects a robust phenomenon.

The relationship between post-whiplash complaints and PTSD symptomatology was especially pronounced for the PTSD-related hyperarousal symptoms. The mean number of hyperarousal symptoms was three to five times higher among participants with post-whiplash syndrome at all three assessment points. Because the hyperarousal symptom cluster closely resembles anxiety-disorder symptoms, this finding may indicate

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that general anxiety symptoms bear an important influence on the perceived severity of post-whiplash syndrome. The present finding that victims who reported neck complaints visited their general practitioners more frequently than did those who had no neck complaints provides further indication that anxiety is involved. In other words, although a visit to the general practitioner may be interpreted as indicating that the initial symptoms in this group were relatively severe, it may also reflect reassurance-seeking behavior due to relatively high levels of anxiety. One way to test this idea would be to focus on anxiety reduction during initial interventions. If indeed heightened anxiety levels act in a way to inflate whiplash complaints, anxiety reduction should have a beneficial influence on the intensity of whiplash complaints.

In contrast to earlier research, we found no evidence of a relationship between re-experiencing symptoms and post-whiplash syndrome.22,23 One possible explanation could be that we were able to control for hyperarousal symptoms in our analysis. Even after discarding the hyperarousal symptoms, however, we found no significant role for re-experiencing symptoms. The difference may therefore be caused by the present recruitment strategy. It may well be that the relationship between re-experiencing symptoms and post-whiplash syndrome is evident only in victims who have visited an emergency room.

Several earlier studies of post-traumatic stress symptoms have used the Impact of Events Scale.23 While this scale includes the first two major symptom clusters, it does not address hyperarousal symptoms. Our results clearly show that the hyperarousal symptoms have the most marked relationship with post-whiplash syndrome. We therefore recommend that future research on the role of post-traumatic stress disorder in post-whiplash syndrome consider all three symptoms scales. In addition, future research should provide further investigation of the apparent role of hyperarousal symptoms in post-whiplash syndrome.

It should be acknowledged that the present prognostic design does not allow for strong conclusions regarding causal mechanisms that may underlie the co-occurrence of post-whiplash syndrome and PTSD symptoms. Nonetheless, the present pattern of results is clearly consistent with the idea that the concurrent presence of PTSD may have an undesirable influence on the course of whiplash complaints.

One way in which PTSD symptoms may influence the course of whiplash complaints is via the anxiety features of PTSD that may alter the perception and experience of the physical complaints.16

Furthermore, PTSD symptoms may fuel a vulnerability to the misinterpretation

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and catastrophization of the physical sensations that accompany hyperarousal and are associated with pain. These sensations may subsequently be attributed to post-whiplash syndrome or aggravate its symptoms.1,32-34

In addition, anxiety-induced heightened vigilance may inflate the perception of pain.20 Consistent with this idea, the present study has provided evidence that the intensity of PTSD symptoms at Q1 has predictive value for the course of whiplash complaints at follow-up. More specifically, it was found that the presence of a relatively large number of hyperarousal symptoms was related to more intense post-whiplash syndrome complaints at six and twelve months follow-up. These results suggest that general anxiety symptoms are more relevant in this respect than are PTSD symptoms that are more specific (e.g., re-experiencing and avoidance symptoms).

The hyperarousal symptom cluster closely resembles irritability, insomnia, hypervigilance, and similar symptoms. Hypervigilance, which is unique to PTSD, is known to be correlated with higher reported pain intensity, negative affectivity, and catastrophic thinking.35 Accordingly, it may be that symptom amplification and catastrophization may play a role in the consolidation and perceived severity of post-whiplash syndrome, independent of anxiety as such.1 One way to explore this possibility would be to conduct a prospective study to test the predictive value of catastrophic thoughts regarding either the attribution of somatic complaints or the expected course of complaints.

It is important to note that the PTSD hyperarousal scale addresses symptoms regar-ding concentration, memory function, feelings of insecurity, and nervousness. Some of these symptoms are also often attributed to post-whiplash syndrome. It is therefore possible that the predictive properties of the hyperarousal scale are at least partially caused by the fact that this scale measures complaints that are associated with post-whiplash syndrome. The present pattern of results, which indicates that only hyperarousal and none of the other PTSD symptoms are related to the prognosis of post-whiplash syndrome, further substantiates this idea. The present pattern of results is also consistent with the idea that at least some post-whiplash syndrome complaints are, actually symptoms of PTSD. The pattern further highlights the importance of considering PTSD, particularly the hyperarousal features, when diagnosing and treating individuals with apparent post-whiplash syndrome complaints.7

With respect to earlier research, a number of comments are in order regarding the relatively low number of participants who had post-traumatic stress disorder and those who suffered from both post-whiplash syndrome and post-traumatic stress disorder after one month (11% and 16%, respectively).30,36

One explanation might be that research designs that rely on recruiting participants

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from among emergency-room visitors or from referring doctors may overestimate the frequency of post-traumatic stress disorder after motor vehicle accidents, as they may concentrate on a group of victims who are more seriously injured or, more importantly, more frightened than the average victim is. The lower prevalence of post-traumatic stress disorder may therefore have been caused by the fact that we were able to include a considerable number of participants who had not visited an emergency room, or even a medical doctor, following their accidents. The variable findings that are reported in the literature, may thus reflect the nature of samples and methodology, at least in part.37

Additional comments are in order regarding the research sample. The study group consisted of participants who had initiated compensation claim procedures. Since the threshold for starting such procedures is low in the Netherlands, there seems to be no strong reason to suspect that this introduced a bias toward patients whose complaints were more serious.38

First, the damage-report forms that are used for claiming car damage, and which are usually completed within a few days after the accident, contain a section for the names of victims and their complaints. We invited all claimants directly from these forms, including victims who had not visited an emergency room or sought medical help at the time of the accident.

Second, although the insurance company and victims can be seen as opposing parties, most personal injury claims in the Netherlands, even large ones that involve serious injuries, are settled out of court. None of the participants was in actual litigation.

Nevertheless, some studies have recently found that compensation is a critical factor to consider when studying post-whiplash syndrome.39,40

Therefore, the personal injury claimant context should be taken into account when interpreting or generalizing our findings. Furthermore, since the exact nature and expectations of compensation may vary greatly from country to country, we advise caution when extrapolating results of one population onto another.

Finally, it should be acknowledged that post-traumatic stress disorder is not a questionnaire diagnosis. The presence of the minimum number of symptoms required in the three major symptom clusters does not necessarily imply the presence of post-traumatic stress disorder. Structured DSM interviews identify a smaller percentage of victims of post-traumatic stress disorder than do self report questionnaires.27 Questionnaire results, including those that are used here, should therefore be interpreted with caution.

Our results confirm earlier research, which showed that recovery from post-whiplash syndrome after six and twelve months is related to the severity of initial symptoms3-6

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Furthermore, the present results replicated previous findings that indicated that women are over-represented among accident victims with post-whiplash-syndrome.3,6

To conclude, a considerable number of individuals with post-whiplash syndrome were also found to suffer from post-traumatic stress symptoms. More specifically, the number of hyperarousal symptoms at 21 days after the accident was found to be related to the persistence and severity of post-whiplash syndrome symptoms at both six and twelve months follow-up. It is therefore worthwhile to consider symptoms of post-traumatic stress disorder and anxiety in general when evaluating and treating patients with post-whiplash syndrome after motor vehicle accidents.

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