Attention to the Body in Non-Clinical Somatoform Dissociation Depends On

Attention to the body in somatoform dissociation 1

Attention to the body in non-clinical somatoform dissociation depends on

emotional state

Richard J. Browna,*, Adam N. Danquaha, Eleanor Milesa, Emily Holmesb

and Ellen Poliakoffa

a. School of Psychological Sciences, University of Manchester, Oxford Road,

Manchester, M13 9PL, United Kingdom. b. Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford

OX3 7JX, United Kingdom.

Running header: Attention to the body in somatoform dissociation Attention to the body in somatoform dissociation 2

ABSTRACT

Objective

Unexplained neurological symptoms (“somatoform dissociation”) are common in healthcare settings and associated with disproportionately high levels of distress, disability and resource utilization. Theory suggests that somatoform dissociation is associated with disturbed attentional processing but there is a paucity of research in this area and the available evidence is contradictory.

Methods

We compared undergraduate participants (n = 124) with high and low scores on the Somatoform Dissociation Questionnaire (SDQ-20) on a tactile cueing paradigm measuring the time-course of attention to touch, following either a neutral film or a film designed to simulate the emotional effects of trauma exposure.

Results

Following the neutral film, high SDQ-20 participants exhibited delayed disengagement from tactile cue stimuli compared to the low SDQ-20 group.

Following the “trauma” film, however, the high SDQ-20 group showed attentional effects suggesting avoidance of the tactile stimuli in this condition. Early attention to tactile cues following the trauma film predicted film-related intrusive thoughts after the experiment.

Conclusion

These findings suggest that both body-vigilance and body-avoidance may be involved in the expression of somatoform dissociation.

KEYWORDS: pseudoneurological symptoms; medically unexplained symptoms; attentional bias; attention; cue-target task; trauma film paradigm Attention to the body in somatoform dissociation 3

INTRODUCTION

Physical symptoms that lack an identifiable medical cause (i.e. “medically unexplained symptoms”; MUS) are common in medical settings (1) and associated with high levels of distress, disability and resource utilization (2,3). While MUS can be associated with any bodily system, the worst cases often have an unusually high preponderance of unexplained neurological symptoms, such as motor (e.g. paralysis), paroxysmal (e.g. convulsions) and sensory complaints (e.g. blindness; 4,5). Current taxonomies disagree in their classification of such “pseudoneurological” symptoms, reflecting on-going uncertainty about the nature of these conditions (6,7). One influential model spans existing taxonomies by describing pseudoneurological symptoms as examples of “somatoform dissociation” (8).

Following Janet (9), most theorists suggest that disturbances in attention play a central role in unexplained neurological symptoms. Ludwig (10) argues for an impairment in attention characterised by top-down inhibition of afferent stimuli, whereas Kihlstrom (11) suggests that a disturbance in high- but not low-level attentional processes is responsible. More recently, Brown (12,13) has argued that many unexplained neurological symptoms are disturbances in bodily awareness and control resulting from the over-activation of somatic representations in memory. In this account, attentional hypervigilance for symptom-related information and difficulties disengaging attention from somatic representations both contribute to the creation and maintenance of these symptoms. In many models, exposure to traumatic events is thought to contribute to these attentional vulnerabilities.

Attentional processes are also central in cognitive behavioural accounts of

MUS more generally. Excessive body-focused attention (somatic hypervigilance) is thought to increase the salience of benign bodily sensations, causing them to be Attention to the body in somatoform dissociation 4 misinterpreted as evidence of serious illness; the resulting physiological and behavioural changes lead to further physical sensations, creating a vicious cycle (20).

The term “somatosensory amplification” refers to this process of focusing on and misinterpreting somatic sensations (21), individual differences in which are typically measured using the Somatosensory Amplification Scale (SSAS; 21,22).

There is evidence that MUS are associated with deficits in attentional vigilance and mental set-shifting (14), automatic and voluntary orienting (15), and disengaging attention from stimuli (15-19). Some studies have found that MUS patients attend more to illness-relevant stimuli than controls (23-25), although this has proved difficult to replicate (26-30). In terms of more direct measures of body- focused attention, one study found that high SSAS scorers were poorer than low scorers at detecting physiological events (heartbeats), suggesting an attentional deficit in the former (31); two other studies have found no relationship between SSAS scores and heartbeat detection, however (32,33). One recent investigation (34) found that

SSAS scores were negatively correlated with a performance measure of tactile (i.e. bodily) attentional bias following exposure to body-related stimuli. After controlling for SSAS scores, however, non-clinical participants with high self-reported somatoform dissociation still showed the expected increase in tactile bias when exposed to threatening body-related pictures. These latter findings suggest that attention towards and away from the body might both be relevant in somatoform dissociation.

Despite much theorising about attention in MUS, there remains a paucity of empirical data, particularly regarding somatoform dissociation. Moreover, the available literature is largely unable to identify the precise attentional processes in question. Accordingly, the current paper describes a study investigating the Attention to the body in somatoform dissociation 5 relationship between somatoform dissociation and performance on a well-validated attention measure, the exogenous cue-target task (35). There is evidence from a visual cue-target task that patients with pseudoneurological symptoms have difficulties in disengaging visual attention (15). We used a tactile version of this task (36,37) to measure how attention is drawn to, and disengaged from, touch stimuli, which is arguably more relevant to body-related attentional processes. Since somatoform dissociation is a trait-like phenomenon distributed across both normal and clinical populations (8), we sampled non-clinical participants with either high or low scores on the SDQ-20 (38) and compared their performance on the task.

We investigated the association between traumatic affect and somatoform dissociation by presenting half of the participants with the task in the context of a neutral film, and half in the context of a film to mimic the emotional after-effects of trauma. The trauma film paradigm has long used been as an experimental analogue to test the emotional consequences of stressful events, such as later film-related intrusive memories (39). It has been used in a range of studies to examine forms of dissociation

(e.g. 40,41) and more recently to probe the impact of somatoform dissociation on intrusive memories (42). Film-related intrusive thoughts (typically in the form of intrusive images of scenes from the film) are monitored using a self-report diary for one week after the experiment, allowing a controlled test of vulnerability factors related to the impact of a stressful event.

METHOD

Design and overview of procedure

A 2 × 2 × 2 × 4 mixed-model design was used. Film condition (neutral; trauma) and SDQ-20 group (low; high) were between-subjects factors; time (pre-film; post-film) and SOA (150ms; 350ms; 500ms; 1000ms) were within-subjects factors. Attention to the body in somatoform dissociation 6

Participants initially completed an on-line version of the SDQ-20; those meeting SDQ-20 inclusion criteria were invited to participate in the experimental session. The session began with questionnaires measures of trauma exposure, trait anxiety, somatosensory amplification, current mood and current physical symptoms.

They were then given an overview of the cue-target task, followed by a practice block and the experimental blocks. Participants then watched either a neutral or “traumatic” film, re-rated their current mood and physical symptoms, and completed the cue- target task for a second time, comprising the experimental blocks only. They were then presented with a diary to record their physical symptoms and film-related intrusive thoughts in the week following the experimental session. Upon return of the diary, participants were debriefed and received course credit or £5 towards expenses.

Participants

One hundred twenty four students (98 female; mean age = 20.7yrs, SD =

3.2yrs) were recruited. There were no significant differences in age (F(1, 124) =

1.527; p > 0.1) or gender (all p’s > 0.1) between the groups and conditions. Ethical approval for the study was obtained from the relevant committee.

Materials

The “trauma” film was a fourteen-minute compilation of three scenes from commercial feature films1, depicting rape, murder and torture. To provide an experimental analogue of psychological trauma (39), the film content was consistent with DSM-IV criterion A1 (i.e. an event involving actual death or threat to life, or threat to physical integrity). The neutral film was a thirteen-minute compilation of three scenes from films depicting neutral human activity, including talking at home, talking in and around a courtroom, and eating at a café. In line with previous studies,

1 Details available upon request. Attention to the body in somatoform dissociation 7 each scene was preceded by a synopsis of the scenario, presented for approximately

40 seconds (41,43,44). Films were shown on a laptop computer with a 14.1inch screen. Stratified random allocation ensured that equal numbers of high and low SDQ participants were allocated to the conditions.

Self-report measures

Somatoform Dissociation Questionnaire (SDQ-20)

The SDQ-20 (38) was used to estimate the tendency to experience somatoform dissociation. Each of twenty items describes a symptom; respondents rate the degree to which this has applied to them in the past year, using a five-point Likert scale from

1 (not at all) to 5 (extremely). Total scores ranging from 20 to 100 were computed following (45), with 20 indicating that the participant had not experienced any of the symptoms. Scores of ≥28 and ≤ 22 were taken as cut-offs for membership of the high and low SDQ groups respectively, in line with population norms for the scale (46).

The SDQ-20 was selected in preference to other symptom measures because it focuses specifically on symptoms in the neurological domain (e.g. sensory loss, paralysis, seizures etc.). As such, scores on the measure are less likely to be contaminated by symptoms arising from minor physical ailments, or the somatic concomitants of depression and anxiety (e.g. autonomic arousal), and therefore provide a purer estimate of “true” somatoform dissociation.

State-Trait Anxiety Inventory, Trait Scale (STAI-T)

The trait scale from the State-Trait Anxiety Inventory (47) was used to measure trait negative affectivity. The scale consists of twenty statements (e.g. “I lack self confidence”) that are rated on a four-point Likert scale ranging from 1 (not at all) to 4 (very much so). Total scores range from 20 to 80. STAI-T scores were used as a Attention to the body in somatoform dissociation 8 covariate to control for the effects of negative affectivity, which is commonly associated with the tendency to experience physical symptoms (48)

Trauma Assessment for Adults (TAA)

An abridged version of the TAA (49) was used to ensure that participants in the neutral and trauma conditions were comparable in terms of exposure to potentially traumatic events. Scale items are based on the Potential Stressful Events Interview used in the DSM-IV field trial (50). Thirteen items, relating to twelve specific potentially traumatic events (e.g. “Before you were age 18, has anyone ever used pressure or threats to have sexual contact with you?”) and one ‘other’ category, are presented. Respondents indicate whether they have experienced an event or not, using a yes-no response format. A count of positively endorsed events allows for a trauma history score ranging from 0 to 13.

Somatosensory Amplification Scale (SSAS)

The SSAS (21) is a measure of the tendency to notice ambiguous, but largely benign, sensory events and to experience them as unpleasant. The scale consists of 10 statements (e.g. “I am often aware of various things happening within my body”), rated on a five-point Likert scale ranging from 1 (not at all true) to 5 (extremely true).

Total scores range from 10 to 50. Following (34), the SSAS was used to control for individual differences in the tendency to experience tactile stimulation as aversive, rather than as a trait measure of body-focus per se.

Symptom Checklist

A modified Symptom Checklist (51) was used to measure participants’ experience of a range of common physical symptoms before and after the films.

Symptoms were anchored on seven-point unipolar scales, ranging from the absence of a symptom through increasing degrees of its presence (e.g. “No headache” to Attention to the body in somatoform dissociation 9

“headache”). In the version adapted here, ‘pain’ and ‘fatigue’ were added as these are two of the most frequently observed MUS (52), as was an ‘other’ category. A total sum score from 0 to 90 was obtained by summing scores for each symptom. We used

ANCOVA to control for post-film symptom totals (when film conditions were considered in isolation during the analysis), allowing us to establish whether any attentional effects were due to between-group differences in physical symptoms.

State mood measures

We measured current mood (‘happy’, ‘anxious’, ‘depressed’, ‘angry’) before and after the films using eleven-point scales ranging from 0 (‘not at all’) to 10

(‘extremely’). ‘Distress’ was measured post-film only. We measured current mood to check that our trauma manipulation had the anticipated effect on emotional state.

Symptoms and intrusions diary

Following (41), participants completed a Symptoms and Intrusions Diary comprising daily Symptom Checklists and sections for identifying intrusive thoughts

(and their associated distress) related to the films during the week following the experiment. Total number of intrusive thoughts and total intrusion-related distress were multiplied to produce a composite intrusion burden variable. We anticipated that participants in the trauma condition would report significantly higher intrusion burden than those in the neutral condition, analogous to the effect of traumatic events on intrusive symptom experience in patients with PTSD. We also predicted that this effect would be significantly greater for the high SDQ-20 participants, based on the assumption that the trauma film would have a greater emotional impact on these participants. In order to assess whether attention to the body predicted intrusion burden following the trauma film, we looked at the correlation between post-film cueing effects and intrusion burden for participants in the trauma condition. Attention to the body in somatoform dissociation 10

Cue-target task

A tactile cue-target task (36,37) was used to measure attention to the body.

Participants made a speeded judgement about the frequency of a tactile target (high or low frequency vibration) presented to one of the hands, which was preceded by a cue vibration presented to either the same or the opposite hand. The time between cue and target (stimulus-onset asynchrony; SOA) was varied to measure the time-course of attention to the cue. At short SOAs responses are quicker when the cue and target are presented at the same location (cued trials) than at the opposite location (uncued trials), reflecting automatic attention to the cued location (37). Conversely, at longer

SOAs participants are slower to respond on cued than uncued trials (36,37); this

“inhibition of return” effect is thought to arise because attention is slower to return to a location it has recently disengaged from (53).

To minimise the impact of speed/accuracy trade-offs, performance in each condition was calculated using inverse efficiency (IE) scores (IE = reaction time/[1 – proportion of trials in which the wrong response was made]). IE scores for targets presented to the same hand as the cue (cued) were subtracted from IE scores for targets presented to the opposite hand (uncued) to produce a cueing effect estimating the influence of the cue on exogenous (i.e. ‘stimulus driven’) attention. Higher scores on this measure indicate greater benefits of being cued to the location of the target and/or lower costs of being cued to an irrelevant location.

Participants were centred 35cm in front of a 17-inch monitor with their arms approximately 15cm either side of this midline. A 1cm cross at the screen centre

(approximately 1.6° of visual angle) was used as a fixation point. Tactile stimuli were delivered via vibrotactile bone conductors (Oticon Limited, B/C 2-PIN, 100 Ohm,

Hamilton, UK) within two 9×7×4cm foam cubes. Stimuli were produced using digital Attention to the body in somatoform dissociation 11 sound files run through an amplifier (Dancer Design TactAmp 4.2). The “buzz” cue was a 10ms stream of white noise. The targets were 300ms trains of square waves.

The “high” and “low” target vibrations had frequencies of 200Hz and 40Hz respectively. Participants matched the subjective intensities of the high vibrations across left and right conductors before the task.

Participants placed their right foot on two pedals, so their toes rested on the foremost pedal and their heel, the rearmost. Half the participants were instructed to raise their toes in response to a high vibration and their heel in response to a low vibration. The other half were given the opposite instruction. Participants were played white noise through a sound-attenuating headset to prevent them from hearing the vibrations.

Participants were informed that they would receive a “quick buzz” followed by a “high or low vibration”, and instructed to identify the vibration as high or low as quickly and accurately as possible. The fixation point then appeared and, after a random interval between 700 and 1000ms, the cue was presented to one of the participant’s index fingers. The target was presented following a variable delay from the start of the cue (150, 350, 550 or 1000ms SOA), to enable both attentional facilitation and disengagement to be measured (37).The target was presented to the cued index finger on 50% of trials (i.e. the cues did not predict target location). If participants correctly identified the frequency, the trial terminated and the screen went blank. If they did not respond within 1400ms, ‘no response’ was displayed. If they responded incorrectly, ‘wrong’ was displayed. An interval of 1000ms separated the response to one trial and the start of the next.

A practice block of 30 trials was presented followed by 160 experimental trials split into 3 blocks; participants could rest between blocks. Twenty trials were Attention to the body in somatoform dissociation 12 presented in each of the 8 conditions [Cue location (cued, uncued) x SOA (150, 350,

550, 1000)]. In each condition, target type (high vs. low frequency) and location (left vs. right hand) were balanced but not analysed.

Analysis

Prior to analysis, errors were removed from the tactile-attention data. Trials where participants made the wrong response, or responded prematurely (reaction times < 150 ms) or very late (> 1200 ms) were deemed invalid and excluded (9.6% of all data). In order to remove comparatively long and short reaction times, a within- subjects outlier procedure was used to remove reaction times n standard deviations from the mean, where n was adjusted as a factor of sample size (54). This avoids potential distortions when sample size (i.e. number of errors) differs in different conditions and participants. IE scores were then calculated for each participant in each condition. Finally, cueing effects (IE uncued trials – IE cued trials) were computed for each participant in each condition.

Non-normal variables (post-film anxiety, depression, anger and distress) were transformed using square root and log transformations as appropriate, following the recommendations of (55). Intrusion burden remained non-normal following transformation so was analysed untransformed. Corrections were applied in cases where the assumption of sphericity for repeated measures ANOVA was violated (56).

Analyses were conducted first without and then with STAI-T, TAA and SSAS scores as covariates. Where repeated measures ANCOVAs were performed, the relevant correction (57) was applied to all covariates.

RESULTS

Group comparability Attention to the body in somatoform dissociation 13

Table 1 presents descriptive statistics for the questionnaires. Between-subjects

MANOVA revealed a significant main effect of SDQ-20 group (F(4, 117) = 70.63, p

2 2 < .001, ηp = 0.707); the main effect of film (F(4, 117) = 1.39, p = .241, ηp = .045)

2 and the group × film interaction (F(4, 117) = 1.43, p < .230, ηp = .046) were non- significant. F tests revealed that participants in the high SDQ-20 group scored significantly higher on all of the measures: SDQ-20, F(1, 120) = 270.43, p < .001,

2 2 ηp = .693; STAI-T, F(1, 120) = 10.81, p = .001, ηp = .083; TAA, F(1, 120) = 23.83, p

2 2 < .001, ηp = .166; SSAS, F(1, 120) = 14.88, p < .001,ηp = .110.

TABLE 1 HERE

Manipulation checks

Table 2 indicates that the film manipulations had the expected effects on mood and distress. Four ANCOVAs (for Happy, Anxious, Depressed, and Angry mood) assessed whether post-film mood was significantly different between the two film conditions, after controlling for differences in pre-film mood. In each case, post-film mood was the dependent variable, SDQ-20 group and film condition were between- subjects variables, and pre-film mood was the covariate. The film manipulation proved successful, with significant main effects of film condition for Happy mood,

2 F(1, 119) = 108.18, p < .0001, ηp = .476; Anxious mood, F(1, 119) = 99.66, p < .

2 2 0001, ηp = .456; Depressed mood, F(1, 119) = 46.33, p < .0001, ηp = .280; and

2 Angry mood, F(1, 119) = 91.59, p < .0001, ηp = .435. There were no significant main effects of SDQ-20 group, and no significant SDQ-20 group × film interactions (all p >

0.1). Between-subjects ANOVA indicated that distress (only measured post-film) was

2 significantly greater after the trauma film, F(1, 120) = 175.58, p < .0001, ηp = .594; the main effect for SDQ-20 group and the group × film interaction were both non- significant (p > 0.1). Attention to the body in somatoform dissociation 14

TABLE 2 HERE

Are there differences in tactile attention between groups and conditions?

Table 3 presents raw cueing effects (operationalised as IE for uncued trials minus IE for cued trials). An initial SOA  time  SDQ group  film mixed-model

ANOVA revealed a near-significant four-way interaction between the factors

2 (F(2.930, 351.577) = 2.204, p = .089, ηp = .018) and a significant main effect for

2 SOA (F(2.898, 347.730) = 4.86, p < .01, ηp = .032). When controlling for STAI-T,

SSAS and TAA scores, the four-way interaction became significant (F(3,351) =

2 2.802, p < .05, ηp = .023).

TABLE 3 HERE

Mixed model ANCOVAs were performed for each of the SOAs, controlling for pre- film cueing effect at the corresponding SOA. Figure 1 presents mean post-film cueing effect data. For the 150ms and 550ms SOAs, there were no significant main effects or interactions. For the 350ms SOA, there was a significant group  film interaction

2 (F(1, 119) = 4.306, p < .05, ηp = .035). This interaction was attributable to significantly higher cueing effects for the high SDQ participants in the neutral

2 condition, compared to those in the trauma condition (F(1, 59) = 4.202, p < .05, ηp

= .066). There was also a significant group  film interaction at the 1000ms SOA

2 (F(1, 119) = 5.022, p < .05, ηp = .040). This was mainly attributable to a significantly greater cueing effect for the high SDQ participants in the neutral

2 condition (F(1, 59) = 5.425, p < .05, ηp = .084). Additional analyses indicated that these findings could not be attributed to significant differences between the groups or conditions in overall reaction times. Moreover, all of the group film interactions and follow-ups at 350ms and 1000ms remained significant when STAI, SSAS, TAA, post-film distress and post-film symptoms (follow-up tests only) were controlled. Attention to the body in somatoform dissociation 15

FIGURE 1 HERE

The low SDQ group exhibited significant post-film facilitation effects (i.e. cueing effect significantly > zero) at the 150ms SOA in both neutral (t(30)= 2.165, p

< .05, d = .39) and trauma (t(30)= 3.509, p < .001, d = .63) film conditions, followed by decreasing cueing effects across SOAs. Linear contrasts indicated that cueing effects reduced across the SOAs for the low SDQ group in both neutral (F(1,30) =

2 2 5.789, p < .05, ηp = .162) and trauma (F(1,30) = 4.767, p = .05, ηp = .137) conditions.

There was a trend for higher post-film cueing effects for this group across all SOAs

2 following the trauma film compared to the neutral film (F(1,60) = 3.619, p = .062, ηp

= .057). This effect was borderline significant when controlling for STAI-T, SSAS

2 and TAA scores (F(1,57) = 3.881, p = .054, ηp = .064).

The high SDQ group showed a different pattern of post-film cueing effects.

Unlike the low SDQ group, they did not show a significant cueing effect following the neutral film until the 350ms SOA (t(30)= 3.116, p < .005, d = .56) and this was also present at 1000ms (t(30)= 2.113, p < .05, d = .15). Following the trauma film, no significant effects were observed for the high SDQ group at any of the SOAs, with cueing effects remaining relatively static over time.

Does attention to the body predict subsequent film-related intrusive thoughts?

Table 4 presents diary data. Seventeen diaries were not returned (two from each of the low SDQ groups, six from the high SDQ neutral group and five from the high SDQ trauma group). Factorial between-subjects ANOVA revealed that the high

SDQ group reported significantly more physical symptoms than the low SDQ group

2 (F(1,103) = 25.673, p < .0001, ηp = .20) and participants in the trauma condition reported significantly more physical symptoms than those in the neutral condition

2 (F(1,103) = 6.238, p < .05, ηp = .057); the group  film was non-significant. Factorial Attention to the body in somatoform dissociation 16 between-subjects ANOVA conducted on intrusion burden revealed significant main

2 effects for group (F(1,89) = 6.592, p < .05, ηp = .069) and film (F(1,89) = 11.698, p

2 < .001, ηp = .116) and a significant group  film interaction (F(1,89) = 5.434, p < .05,

2 ηp = .058). Intrusion burden was significantly greater following the trauma than

2 neutral film for both the low (F(1,46) = 7.123, p < .01, ηp = .134) and high (F(1,89) =

2 8.10, p < .01, ηp = .159) SDQ groups. In addition, intrusion burden was significantly higher for the high SDQ group compared to the low SDQ group following the trauma

2 film only (F(1,45) = 6.193, p < .05, ηp = .121). There was a significant positive partial correlation between post-film cueing effect at the 150ms SOA and intrusion burden for participants in the trauma film condition when controlling for SSAS, STAI-T and

TAA scores and pre-film cueing (rp(41) = 0.346, p < .05); when analysed separately, this correlation was found in the high (rp(17) = 0.454, p = .05) but not the low SDQ group (rp(18) = -0.013, p > .10).

DISCUSSION

Low-SDQ participants showed a typical pattern on the cue-target task, characterised by a significant positive cueing effect at the 150ms SOA, followed by a linear decrease in cueing effect across SOAs (53). A similar pattern was observed in both film conditions for this group, with cueing effects being greater across all SOAs following the trauma film when controlling for covariates. This adds to literature indicating that attentional cueing effects, even to neutral stimuli, are influenced by affective state (e.g. 58).

Different patterns of tactile attention were observed in the High-SDQ group, however, which were not explained by between-group differences in adverse life events, trait anxiety and somatosensory amplification. High-SDQ participants in the neutral film condition did not exhibit a significant cueing effect until the 350ms SOA, Attention to the body in somatoform dissociation 17 which was also present at 1000ms. Cueing effects at 1000ms in the neutral condition were significantly greater for the high- than low-SDQ group. This continued cueing effect at 1000ms is consistent with delayed disengagement of attention from the tactile cue for high-SDQ participants. We interpret this finding as evidence of a disturbance in body-focused attention for individuals with high SDQ-20 scores under normal conditions, characterised by a disproportionate duration of attention to bodily cues. It is unclear why this effect only manifested post- and not pre-film, although task practice is a likely factor.

The high-SDQ group did not exhibit significant cueing effects at any SOA following the trauma film, with a significantly lower cueing effect at 350ms in this condition compared to the neutral film. This finding casts doubt on the idea that individuals predisposed to somatoform dissociation become more symptom- or body- focused when anxious or following exposure to trauma-like events (cf. 13). Rather, this finding suggests that high-SDQ participants were less affected by the tactile cue following the trauma film, perhaps due to avoidance of (i.e. faster disengagement from) bodily information. This finding cannot be attributed to general threat-related reaction time differences, as overall RTs were comparable across groups and conditions (cf. 59). Similarly, covariance analyses showed the effect was not attributable to differences in anxiety or physical symptoms post-film.

Although this finding appears to contradict theories that emphasise hypervigilance (e.g. 13,20), it is likely that covert or cognitive avoidance of bodily sensations supplements overt behavioural avoidance, which is often thought to contribute to the creation and maintenance of these conditions. Relatedly, attending towards (i.e. hypervigilance) and away (i.e. avoidance) from threat are both implicated in anxiety states (60,61). Early hypervigilance is thought to enable a rapid Attention to the body in somatoform dissociation 18 response to threatening stimuli, with subsequent avoidance helping to minimise threat-related negative affect (60). It is noteworthy that attention to the tactile cue at

150ms predicted intrusion burden in the week following the trauma film, indicating that early attention to the body was associated with the later emotional reaction of high SDQ participants. From a dissociation perspective, subsequent avoidance of distressing somatic and emotional cues may maintain the separation of dissociated systems, conferring vulnerability to somatoform symptoms (62).

Another interpretation, which augments rather than replaces other accounts, is that avoidance or suppression of somatic information may lead to greater reliance on mental representations of the body during creation of the conscious body image. Such reliance may lead to over-activation of somatic representations in memory, resulting in their mistaken selection as an account of the current body state (13). As a result, these “rogue” representations create a distortion in awareness in the form of unexplained physical sensations or symptoms. By this view, treatment should concentrate on deactivating these rogue components of the body image, reactivating more adaptive body representations and minimising hypervigilance and cognitive- avoidance effects (13).

Whereas previous studies have typically used paradigms that provide only an indirect assessment of bodily hypervigilance, the tactile-cueing paradigm provides more direct evidence concerning disturbed tactile (i.e. bodily) attentional processes in individuals predisposed to somatoform dissociation. This paradigm only tells us about shifts of attention within the tactile modality, however, and not whether participants are disproportionately biased towards the body compared to other modalities.

Therefore, the effects observed in this study may be attributable to a general deficit in spatial attention affecting multiple modalities. Evidence for delayed visual Attention to the body in somatoform dissociation 19 disengagement in patients with unexplained paresis is consistent with a supra-modal deficit in attention disengagement (15). Measuring modality bias (34) or the cost of switching between modalities (63) could provide a method of investigating attention towards the body in future studies. It would also be instructive to investigate the effect of aversive physical cues on the time course of somatic attention, which would provide a closer analogue of MUS than the benign cues (i.e. vibrations) used here.

Vibrations are nevertheless useful in that they allow the effect of threat to be separated from the influence of tactile attentional processes generally.

One potential limitation of this study is the nature of our trauma film. It simulated the effects of being exposed to a generic stressor, and induced changes across a range of affective and physical dimensions. It is therefore impossible to conclude which aspects of the manipulation were responsible for the attentional effects observed here. Similarly, our trauma and neutral films could have been matched more closely in terms of the physicality of the acts portrayed. Future research may benefit from contrasting different films or the use of emotional manipulations tailored to the specific concerns of patients with somatoform dissociation, using more closely matched controls.

Our use of a questionnaire measure of somatoform dissociation many mean that our findings are only relevant to individuals with a propensity towards subclinical unexplained neurological symptoms. Although our study would have been enhanced by the use of a gold-standard interview method of assessing somatoform dissociation, the SDQ-20 is nevertheless a well-validated measure of somatoform psychopathology with good discriminant validity (8). Our high SDQ-20 group not only had comparable

SDQ-20 scores to diagnosed MUS patients (64), but also clinical features commonly associated with these complaints, such as elevated somatosensory amplification, high Attention to the body in somatoform dissociation 20 trait anxiety and a history of potentially traumatic life events (44,65,66). Moreover, our high-SDQ group experienced more physical symptoms in the week following the experiment. It is well-established that physical-symptom reports strongly predict disproportionate disability, healthcare utilisation and psychopathology (3,67). In addition, the high-SDQ group reported more film-related intrusive thoughts and distress than the low-SDQ group. These findings require extension to clinical populations before firm conclusions can be drawn regarding the role of bodily hypervigilance and avoidance in somatoform dissociation. Nevertheless, this study is the first to show that attention towards and away from the body may both be implicated in MUS and suggests that further research in this area is warranted.

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Table 1: Means and standard deviations of screening questionnaire scores for the four

study groups.

SDQ-20a STAI-T TAA SSAS SDQ-20 Film Median IQ Mean SD Mean SD Mean SD group condition R Trauma 32 6 47.42 9.36 2.23 1.43 32.26 7.38 Neutral 31 7 46.35 10.64 1.61 1.61 32.13 6.05 High Total 31 6.25 46.89 9.95 1.92 1.54 32.19 6.69

Trauma 20 1 41.77 10.39 0.81 1.11 29.81 6.64 Neutral 20 2 40.32 9.07 0.77 0.88 25.19 5.05 Low Total 20 1 41.05 9.70 0.79 0.99 27.50 6.30 SDQ-20 = Somatoform Dissociation Questionnaire; STAI-T = State-Trait Anxiety Inventory, Trait

Version ; TAA = Trauma Assessment for Adults ; SSAS = Somatosensory Amplification Scale; IQR =

Interquartile range; SD = Standard deviation;.

a. Median and interquartile range shown due to non-normality of this variable for the high SDQ-20

group in the trauma film condition 30

Table 2: Medians of manipulation-check measuresa (inter-quartile ranges in parentheses)

N = 124 Condition Measure Neutral film Trauma film

Happy Pre-film 6.00 (3) 7.00 (1) Post-film 6.00 (2) 3.00 (3)

Anxious Pre-film 3.00 (3.3) 3.00 (3) Post-film 2.00 (3) 6.00 (4)

Depressed Pre-film 2.00 (3) 2.00 (2) Post-film 1.00 (3) 4.00 (4)

Angry Pre-film 0.00 (1) 0.00 (1) Post-film 0.00 (1) 4.50 (5)

Physical Pre-film 12.5 (12.7) 13.0 (15.4) symptoms Post-film 7.75 (10.5) 24.0 (24.7)

Distressed 0.00 (1) 7.00 (2)

(post-film only) a. Data are collapsed across groups as there were no significant between-group differences 31

Table 3: Mean pre- and post-film inverse efficiency at all SOAs for the two SDQ groups in the two film conditions (standard deviations in parentheses)

SDQ group SOA Mean inverse efficiency

Neutral film (n = 62) Trauma film (n = 62)

Pre-film Post-film Pre-film Post-film

Low 150 5.04 (44.3) 16.32 (42.0) 21.21 (44.7) 18.35 (29.1) 350 7.59 (38.5) 1.87 (34.7) 8.91 (45.7) 10.59 (36.4) 550 9.60 (42.0) -4.53 (30.9) 4.43 (29.2) 9.22 (28.8) 1000 -0.12 (41.4) -6.91 (35.8) 10.29 (42.9) 2.19 (23.0) High 150 23.90 (64.9) 11.08 (54.8) -4.25 (69.5) 11.84 (47.8) 350 13.64 (58.3) 13.48 (24.1) 13.18 (51.7) -2.71 (36.8) 550 15.73 (40.2) -5.89 (38.8) -0.80 (62.7) 1.67 (44.0) 1000 -8.53 (47.3) 15.97 (42.1) -4.24 (36.5) -2.26 (29.3) SOA = Stimulus Onset Asynchrony; SDQ = Somatoform Dissociation Questionnaire 32

Table 4: Descriptive statistics for diary data for the four study groups

SDQ-20 Film Mean physical Median film-related group conditiona symptoms (SD) intrusion burden (IQR)b Neutral 34.0 (38.0) 0.0 (1.75) (n = 29) Low Trauma 56.0 (67.0) 19.5 (108.5) (n = 29)

Neutral 80.0 (93.0) 0.0 (11.0) (n = 25) High Trauma 118.5 (146.8) 162 (400.0) (n = 26)

SD = Standard deviation; IQR = Interquartile range; SDQ-20 = Somatoform Dissociation Questionnaire a. Cell sizes presented to indicate missing diary data b. Median and interquartile range shown due to non-normality 33

FIGURE LEGENDS

Figure 1: Mean post-film cueing effect (indexed by inverse efficiency) across SOAs for low and high SDQ groups, in neutral (panel A) and trauma (panel B) film conditions, controlling for pre-film cueing effect. A positive score indicates superior performance when cue and target were presented at the same, as compared to the opposite location. 34

Figure 1

A: Neutral film B: Trauma film t t c c e e f f f f e e

g 30 g 30 n n i i e # e u 25 ** u 25 C C 20 * 20 y y c c 15 15 n n e e i i c c i i 10 10 f f f f # e e

e e 5 5 s s * r r e e ** v v 0 0 n n I I -5 -5

-10 -10

-15 -15 150 350 550 1000 150 350 550 1000

Stimulus Onset Asynchrony (ms) Stimulus Onset Asynchrony (ms)

Low SDQ High SDQ KEY * Significant difference between conditions for high SDQ group at 350ms SOA (p < .05) ** Significant difference between SDQ groups at 1000ms SOA following neutral film (p < .05) # Difference between conditions for high SDQ group at 1000ms SOA approaching significance (p = .057)

SDQ = Somatoform Dissociation Questionnaire SOA = Stimulus Onset Asynchrony