Acceptance: a factor to consider in persistent pain after neck trauma

1 Introduction

The incidence of neck trauma is reported to be 235/100,000/year [1] and the rate of failed recovery has been estimated to be as high as 50%, with approximately 30% having moderate to severe pain and disability 1 year after a trauma [2]. Even though not all neck trauma is caused by rear-end collisions and the whiplash mechanism, this is the most common type of trauma in patients with persistent pain and dysfunction. Neck trauma can also occur in other circumstances, such as other traffic accidents, sports-related accidents, direct head or neck traumas, falls, and bicycle accidents [1], [3].

During the last few decades, much effort has been put into understanding the traumatic and posttraumatic mechanisms leading to remission or persistent pain and disability after neck trauma [4]. Prognostic factors that have been investigated include parameters of the accident, biological factors and/or factors from clinical assessment, self-reported symptoms or interference at inception, treatment-related factors, pre-injury history, psychological and behavioral factors, medicolegal context and other social influences, and demographics [5].

Poor recovery after neck trauma has consistently been associated with moderate to high initial neck pain intensity, neck-related dysfunction and psychological factors [6]. In recent years, there has been more interest in psychological aspects of neck trauma, reflecting a deeper understanding of the multidimensional nature of pain and disability, and emerging research points to the importance of such factors [7], [8], [9]. “Psychological factors” is an umbrella term for several processes, including the individual’s pre-trauma psychological history [10], acute reaction to the trauma, and the psychological mechanisms affecting the recovery after the trauma. Symptoms of posttraumatic stress [5], [9], [11], [12], pain catastrophizing [2], [5], [12], and to a lesser extent low self-efficacy [9] have consistently been associated with delayed recovery [6]. Fear-avoidance beliefs [2], [12], perceived injustice [13], passive coping, and helplessness [2] have also been described as obstacles in the healing and rehabilitation processes. Furthermore, some studies have connected anxiety [14] and depression [14], [15] to the lack of recovery after neck trauma.

Acceptance is a psychological factor that has rarely been incorporated in management and treatment of posttraumatic neck pain [7], [8], [16], even though several studies have demonstrated associations between acceptance and improved outcomes in more diverse chronic pain samples [17], [18], [19], [20], [21]. Three recent studies have also linked acceptance strategies to improved pain-related functioning and life satisfaction after neck trauma [18], [22], [23], but studies on the interaction between acceptance and pain-related processes in such populations are to our knowledge still sparse [7], [8], [16]. Pain-related acceptance can be defined as the conscious embrace of pain, when attempts to avoid, control, or reduce pain impact negatively on overall functioning. Such strategies are focused on behaving in line with chosen goals even in the presence of challenging or painful experiences. Acceptance is sometimes referred to as openness or willingness [20], [24] and it is an important process in Acceptance and Commitment Therapy [25], [26], [27], an empirically-supported treatment for chronic pain [26]. The aim of the present study is to investigate how acceptance relates to persistent pain in patients after neck trauma, when controlling for the influence of other psychological factors, trauma characteristics, and demographic variables. Based on previous studies, we predict that acceptance will function as a predictor over and above the influence of the other predictors for all outcomes [18], [22].

2 Materials and methods

3 Results

3.1 Descriptive statistics and missing data

Descriptive statistics are provided for all continuous variables in Table 1. The total percentage of missing variables was 1.8%. We used a multiple imputation method from the RMS package [37] for R to impute missing data. The error associated with the imputation was incorporated into the following analyses.

Table 1:

Descriptive statistics for all the continuous variables in the sample.

	n	Mean	SD	Median	1st quartile	3rd quartile
Age	565	39.6	11.5	39.0	30.0	48.0
Time since trauma in months	565	58.9	70.9	26.0	12.0	84.0
Anxiety	553	10.0	5.0	10.0	6.0	14.0
Depression	555	9.4	4.9	9.0	6.0	13.0
Acceptance	474	18.4	8.8	18.0	12.0	25.0
Pain interference	556	4.6	1.0	4.7	4.0	5.4
Pain severity	559	4.7	0.9	4.7	4.0	5.3

1. Anxiety and depression were measured with the Hospital Anxiety and Depression Scale (0–7 for non-cases; 8–10 for doubtful cases; and 11–21 for cases); acceptance with the Chronic Pain Acceptance Questionnaire-8 (min=0; max=48); pain interference and pain severity with the Multidimensional Pain Inventory (min=0; max=6).

The distribution of the patients’ age and time since trauma (in months) were concentrated towards the lower end of the scales (right-skewed), particularly time since trauma, whilst pain interference and severity exhibited the opposite pattern (left-skewed). There was considerable variation in the number of months (time) since the trauma with 12 and 84 months at the first and third quartiles, respectively. About two-thirds of the sample were women and one-third had studied at university level. The median age of the sample was 39 years (Table 1). Most of the patients (50%) were diagnosed with regional pain whilst local pain was the least common category of pain distribution (11%). Approximately 78% of the patients had been in a motor vehicle collision. Descriptive statistics for type of trauma and pain distribution are summarized in Table 2.

Table 2:

Counts of type of trauma and pain distribution with within-rows percentages.

Pain distribution	In struck vehicle	In striking vehicle	Other trauma	Total
	n	n	n	n
Local	32 (51%)	14 (22%)	17 (27%)	63 (100%)
Regional	143 (50%)	84 (30%)	57 (20%)	284 (100%)
Widespread	108 (50%)	57 (26%)	53 (24%)	218 (100%)
Total	283 (50%)	155 (27%)	127 (22%)	565 (100%)

Figure 1 outlines pairwise Pearson correlations between some of the variables under study. Strong relationships were seen between depression and anxiety, depression and pain interference, pain severity and pain interference as well as acceptance and pain interference. Meanwhile, age and months since trauma both had weak correlations with the other variables.

Figure 1:

Pearson correlations for the variables under study.

4 Discussion

This study investigated how acceptance relates to persistent pain in patients after neck trauma, when controlling for the influence of other psychological factors, trauma characteristics, and demographic variables. Generally, our models explained much of the variability among individuals in pain interference, but less so for pain severity and the least for pain distribution. In accordance with our hypothesis, acceptance was the only factor associated with all outcomes, and lower acceptance was associated with more widespread pain distribution and greater interference and severity of pain.

Overall acceptance stood out as the most important factor across the different outcomes. For instance, a 10-point decrease in acceptance scores resulted in an estimated increase of pain interference of 0.41 and increase of pain severity of 0.22. These results are in line with those of recent studies that have highlighted the protective role of acceptance in people with chronic pain and traumatic experiences [38], [39], [40]. The results also agree with studies that have connected acceptance strategies to successful management after neck trauma [18], [22], [23] and to various treatment outcomes in persistent pain populations [20], [21], [41], [42], [43].

In the present study, higher depression was associated with both worse pain interference and pain severity, whilst anxiety only mattered significantly for pain severity and not pain interference. For instance, patients who could be considered cases in terms of anxiety and depression [29] were estimated to have at least 0.10 and 0.11 higher scores, respectively, on pain severity compared to non-cases. These results add to literature which connects depression [14], [15] and anxiety [14] to the lack of recovery after neck trauma.

Management and treatment of whiplash-related disorders have, to a large extent, focused on somatic factors [7], [8]. Calls have been made for changes within the current treatment approaches for acute and chronic whiplash-associated disorders to include treatment strategies with a wider scope, also reflecting psychological and behavioral factors [7], [8]. Identification of such factors could be valuable since they can often be reversed by intervention and therefore might assist in the rehabilitation process [2], [12]. In line with this, emerging research points to the importance of acceptance and other psychological factors in failed recovery after neck trauma [7]. Still, few studies have focused on psychological interventions for whiplash-associated disorders and there is limited evidence to support the use of these interventions. Several factors are thought to contribute to this, such as poorly conceptualized and implemented interventions. Studies have also been conducted with non-standard treatment dosages and participants that are unlikely to benefit, such as patients with low initial levels of psychological distress [16]. In addition to this, the goals of psychological strategies, often taken from Acceptance and Commitment Therapy (ACT) and Cognitive Behavioral Therapy (CBT), primarily concern improved functioning and engagement with life goals and values [25], [26], [27]. Hence, interventions and outcome measures within this research field need to incorporate this focus together with outcomes such as pain reduction [16]. Lastly, interventions have often been implemented by professionals other than psychologists, likely with less training in delivering these therapies effectively, which may play a role in patient outcomes [16]. Taken together, further methodologically rigorous research is needed in this field [16].

The results of this study connect anxiety, depression, and acceptance to persistent pain after neck trauma and suggest that interventions targeting these processes may prove effective in preventing the development of chronicity when used together with other interventions. Clinical implementation and longitudinal research on these processes is warranted to assess the extensibility of these results.

Our study also connected the time since the trauma with pain distribution, but not with pain interference or pain severity. The relationship with pain distribution, however, might be characterized as weak, given that an increase in time of 1 year since the trauma only amounts to an estimated 4% increase in risk for a diagnosis of more widespread pain. The type of trauma had no significant relation to any of the outcomes in this study, which supports earlier findings that suggest that type of trauma and other accident-related parameters fail to forecast recovery after neck trauma [2], [5], [44].

Neither age nor education mattered greatly for any outcome, with the only significant relationship being a week association between lower education level and higher pain severity. These results are comparable to those of several previous studies that have found no or negligible effects of age and education on the risk of chronicity after neck trauma [2], [5], [44]. In contrast to the other demographic factors, sex was strongly associated with pain distribution, weakly associated with pain interference and not associated with pain severity. Female sex was related to more widespread pain and greater pain interference. This might be attributed to several factors, including differences in trauma-related mechanisms [45], physiological sex differences [46], [47], and gender differences [48]. Earlier findings of the effect of sex on outcome after neck trauma have been inconsistent, but the results from this study support the studies that have identified associations between female sex and poorer outcomes [2], [5], [44].

We acknowledge several limitations in the current study. First, because of the cross-sectional nature of the data, the investigated factors associated with persistent pain after neck trauma could be risk factors, prognostic factors, or consequences of persistent neck pain. Conclusions about the direction of causation cannot be made from this study i.e. changes in pain/disability level can affect the psychological factors or the reverse. The observed relationships from this study provide a basis for future longitudinal studies that aim to identify prognostic factors of poor recovery after neck trauma. Secondly, our analyses included participants who had missing data on several variables, which we tackled with robust multiple imputation methods. Thirdly, the type of trauma was defined from the reported event (motor vehicle, bicycle, scuffle, amusement ride, etc.) and gives only rough estimates of the supposed trauma mechanisms, and not their severity. Lastly, the sample comprised a large percentage of women with relatively high levels of education and the results may therefore not generalize to more diverse samples.

In summary, the findings of this study add to a growing body of literature proposing that the development of chronicity after neck trauma should be understood as a multidimensional process, best described by a biopsychosocial model [7], [10], [11], [49]. Persistent pain after neck trauma is complex and a wide range of biological, psychological, and social mechanisms have been identified in the recovery process after neck trauma [50]. Professionals in all clinical settings should incorporate psychological factors in their assessments of and interventions with this patient group. In order to further develop assessment and treatment algorithms, studies are needed to both identify key factors of chronicity and to evaluate interventions aimed at targeting these processes in terms of effect and timing in the rehabilitation process. The results from this study suggest that psychological factors and especially acceptance might be important processes with implications for enhanced recovery after neck trauma that should be identified and addressed in the continuous pain rehabilitation process.