Cognitive predictors of posttraumatic stress disorder in children: results of a prospective longitudinal study
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Behaviour Research and Therapy 41 (2003) 110www.elsevier.com/locate/brat
Cognitive predictors of posttraumatic stress disorder inchildren: results of a prospective longitudinal study
A. Ehlers a,*, R.A. Mayou b, B. Bryant ba Department of Psychology, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London SE5 8AF, UK
b Department of Psychiatry, University of Oxford, Oxford, UKAccepted 30 October 2001
The present study explored whether cognitive factors specified in the Ehlers and Clark model (Behav.Res. Ther. 38 (2000) 319) of posttraumatic stress disorder (PTSD) predict chronic PTSD in children whohad experienced a road traffic accident. Children were assessed at 2 weeks, 3 months, and 6 months afterthe accident. Data-driven processing during the accident, negative interpretation of intrusive memories,alienation from other people, anger, rumination, thought suppression and persistent dissociation at initialassessment predicted PTSD symptom severity at 3 and 6 months. On the basis of sex and stressor severityvariables, 14% of the variance of PTSD symptoms at 6 months could be explained. The accuracy of theprediction increased to 49% or 53% when the cognitive variables measured at initial assessment or 3months, respectively, were taken into account. 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Posttraumatic stress disorder; Children; Cognitive predictors; Prospective study; Cognitive model
There is increasing awareness that posttraumatic stress disorder (PTSD) is common in childrenwho have experienced traumatic events such as road traffic accidents (RTAs). Recent estimatessuggest that between 14 and 34% of children involved in an RTA will develop PTSD (e.g. Bryant,Mayou, Wiggs, Ehlers, & Stores, 2001; Canterbury & Yule, 1997; Di Gallo, Barton, & Parry-Jones, 1997; Ellis, Stores, & Mayou, 1998; Mirza, Bhadrinath, Goodyear, & Gilmore, 1998; Stal-
* Corresponding author. Tel.: +44-20-7848-5033; fax: +44-20-7848-0591.E-mail address: email@example.com (A. Ehlers).
0005-7967/03/$ - see front matter 2003 Elsevier Science Ltd. All rights reserved.PII: S0 005- 796 7(01 )001 26- 7
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lard, Velleman, & Baldwin, 1998). Very little is known, however, about factors that contributeto the development and maintenance of PTSD in children.
The present study explored whether psychological variables that have been shown to predictPTSD after an RTA in adults also predict PTSD in children. In previous research with adult RTAsurvivors, objective indicators of trauma severity such as injury severity were poor predictors ofPTSD symptoms. In contrast, the individuals subjective response to the event, in particular theirperceived threat to life, was consistently found to be a significant predictor (e.g. Blanchard et al.,1995; Ehlers, Mayou, & Bryant, 1998; Pynoos et al., 1987; see also review by March, 1993).Nevertheless, subjective stressor severity only explained a small proportion of the variance ofchronic PTSD symptoms. The accuracy of the prediction could be substantially improved if main-taining psychological factors derived from Ehlers and Clarks (2000) model of PTSD were takeninto account (Ehlers, Mayou et al., 1998; Mayou, Ehlers, & Bryant, in press).
The Ehlers and Clark (2000) model highlights three factors thought to determine the develop-ment and maintenance of PTSD.
1. Trauma memory deficits. The memory for the traumatic event is poorly elaborated and inad-equately integrated with other autobiographical information. This leads (together with strongpriming and conditioning for associated cues) to easy triggering of re-experiencing symptomswhen matching cues are present. The deficit in elaboration/integration of the trauma memoryis due to (a) incomplete cognitive processing of the event while it is happening, and (b) cogni-tive avoidance after the event which prevents a change in memory. Ehlers and Clark (2000)specified three overlapping indicators of incomplete processing during the event, data-drivenprocessing (e.g. processing the sensory characteristics of the situation rather than its meaning),lack of self-referent processing, and dissociation.
2. Appraisals. The individual makes excessively negative appraisals of the traumatic event and/orits sequelae (including the initial PTSD symptoms), leading to a sense of current threat (seealso Ehlers & Steil, 1995; Steil & Ehlers, 1995).
3. Maintaining behaviours and cognitive strategies. The negative appraisals motivate the individ-ual to engage in a range of dysfunctional behaviours and cognitive strategies that are intendedto control the perceived current threat, but maintain the problem (see also Ehlers & Steil,1995; Steil & Ehlers, 1995). Examples include thought suppression, avoidance, rumination, andpersistent dissociation.
Evidence for the role of each of these three factors has been accumulated in a series of cross-sectional and prospective longitudinal studies of adult trauma survivors. First, indicators of traumamemory deficits and incomplete processing during trauma (data-driven processing, lack of self-referent processing and dissociation) predicted PTSD in adult RTA and assault survivors (Murray,Ehlers, & Mayou, in press; Halligan, Michael, Clark, & Ehlers, 2001). Second, negative appraisalsof the trauma and its sequelae were strongly related to PTSD severity across a range of differenttraumas (Dunmore, Clark, & Ehlers, 1999, 2001; Foa, Ehlers, Clark, Tolin, & Orsillo, 1999).Common negative appraisals of the trauma in PTSD include overgeneralization of danger, globalnegative thoughts about the self, preoccupation with unfairness and self-blame (Foa et al., 1999;Foa, Riggs, Massier, & Yarczower, 1995). Trauma sequelae that are often interpreted negativelyby trauma survivors include the initial symptoms of PTSD, e.g. intrusive memories may be inter-
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preted as a sign of going crazy (Clohessy & Ehlers, 1999; Ehlers & Steil, 1995; Ehlers, Mayouet al., 1998; Steil & Ehlers, 2000), and the reactions of others in the aftermath of the event thatmay be interpreted as signs of alienation (Dunmore et al., 1999, 2001; Ehlers, Clark et al., 1998;Ehlers, Maercker, & Boos, 2000). Third, several studies of RTA survivors and ambulance staffhave supported the maintaining role of rumination and thought suppression (Clohessy & Ehlers,1999; Ehlers, Mayou et al., 1998; Murray et al., in press; Steil & Ehlers, 2000).
Dissociation has received special attention in many studies. It represents an indicator of incom-plete processing during trauma and is thus thought to lead to problematic trauma memories (e.g.Foa & Hearst-Ikeda, 1996; Spiegel & Cardena, 1990). Indeed, several prospective studies havefound that dissociation during trauma predicts subsequent PTSD (Ehlers et al., 1998; Halligan etal., 2001; Koopman, Classen, & Spiegel, 1994; Shalev, Peri, Canetti, & Schreiber, 1996; Murrayet al., in press). However, dissociation can also be a more persistent response style thought toprevent a change in trauma memories. Murray et al. (in press) and Halligan et al. (2001) foundthat persistent dissociation was a better predictor of PTSD at 6 months after an RTA or an assaultthan dissociation during the trauma.
The present study was designed to explore whether the Ehlers and Clark (2000) model can beapplied to children and adolescents. A prospective longitudinal study assessed children and ado-lescents who had been involved in an RTA at 2 weeks, 3 months, and 6 months. The assessmenthad to be brief to make the study feasible. Therefore, only a few key variables could be chosenfor the investigation:
1. Data-driven processing during the accident, as one of the indicators of incomplete processing.2. Appraisal measures that are thought to lead to a sense of current threat: negative appraisals of
intrusive memories, alienation from other people, and anger as a measure of preoccupationwith unfairness.
3. Dysfunctional cognitive strategies hypothesized to maintain PTSD: rumination, thought sup-pression, persistent dissociation, and, as children often do not have control over exposure toreminders, their parents attitude favouring avoidance strategies to deal with the event.
The study investigated whether these variables predict PTSD severity in children and ado-lescents at 3 and 6 months after an RTA, and whether they predict PTSD over and above whatcan be predicted from measures of objective and subjective stressor severity.
The study was part of an investigation into the prevalence of childrens psychological symptomssuch as posttraumatic stress symptoms, travel anxiety, sleep disturbance, and behavioural problemsin the aftermath of an RTA. The prevalence data are presented in Bryant et al. (2001).
Children resident in Oxfordshire, UK, and aged 516 years who were passengers, pedestriansor cyclists involved in an RTA and who were taken to the emergency department of the John
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Radcliffe Hospital, Oxford, in July 1997July 1998 were recruited into a prospective study. Atotal of 150 children from 137 families were invited to take part in the study. Of these, 86 children(58%) from 80 families agreed to participate. For the 3 and 6 months assessments, data from 81(94%) and 82 (95%) of the children who participated in initial assessment were available. At 2weeks after the accident, 15% of the children met diagnostic criteria for acute stress disorder,and at 3 and 6 months, 25 and 18% of the children met criteria for PTSD, respectively (seeBryant et al., 2001, for a full description).
Non-participation was not related to the age or sex of the child, nor to the type of accident.Those with less severe injury were less likely to take part. Telephone conversations with theparents who declined participation suggested that the proportion of acute stress disorder in non-participants was comparable to that of the participants (see Bryant et al., 2001).
Fifty-five per cent of the participants were boys. Mean age was 12.3 years, SD 2.86. Abouthalf of the participants were teenagers, and one-fifth were under 10 years old. Most of the childrenhad contracted soft tissue injuries (73%), 23% had bony injuries, and 4% remained uninjured; 21had been admitted to hospital.
2.2.1. Symptoms of post-traumatic stress disorderThe dependent variable was the severity of PTSD symptoms as defined by DSM-IV (American
Psychiatric Association, 1994). When the study was planned, the best validated measures of PTSDsymptoms in children (see review by McNally, 1996) were the childrens version of the Impactof Event Scale (IES, Horowitz et al., 1979; childrens version by Yule and colleagues, e.g. Yule &Williams, 1990) and the Child Post-traumatic Stress Reaction Index (RI, Pynoos et al., 1987). Asitems of these scales have been shown to be appropriate for children, we used them to representthe DSM-IV symptoms whenever possible. Participants were instructed to rate the symptoms ona scale from 0 no to 3 yes, often. The total PTSD severity score was the sum of the scoresfor the 17 DSM-IV symptoms. If none of the IES or RI items measured a DSM-IV symptom,the authors constructed a new item; for example, symptom C6 was assessed with the questions:Is it difficult for you to have strong feelings? For example, do you find it hard to get reallyexcited or happy, or do you find it hard to cry when you are sad?. To avoid duplication ofquestions, sleep disturbance was scored from the Sleep Behavior Questionnaire (Simonds & Par-raga, 1982). Some DSM-IV items were represented by two items, for example the IES items Dopictures of the accident pop into your mind and Do you think about the accident even if youdont mean to both represented symptom B1. The maximum score for these items was used inthe overall severity score. For young children, the parent attending the interview (usually themother) complemented the childs answers to the items and also provided information on symp-toms of repetitive play and reenactment.
2.3. Predictor variables
2.3.1. Stressor severity measuresThe Injury Severity Score (ISS) of the Abbreviated Injury Scale (AIS, American Association
for Automotive Medicine, 1985) assessed injury severity. Information was taken from the hospital
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case notes. On the AIS, each injury is coded on a six-point scale from 1 minor to 6 maximum.The ISS is the sum of the squares of the highest AIS score in each of the three most injured ISSbody regions (head or neck, face, chest, abdominal, extremities). In addition, for comparability,two measures of injury severity as used in our previous study of adult survivors of RTAs wereincluded. First, we assessed whether children had no injury, soft issue injuries, or bony injuriesto distinguish between forms of minor injuries. Second, we assessed whether or not children wereadmitted to hospital.
Two measures of subjective stressor severity were taken. First, children indicated whether ornot they thought they were going to get hurt or die (perceived threat to life/physical integrity).Second, they indicated the extent to which they felt scared/frightened during the accident andwhile in hospital on a scale from 1 not scared to 3 a lot. The fear response score was themaximum of these two answers.
As presented elsewhere, characteristics of the accident and the childrens age and previouspsychological problems were not related to PTSD (Bryant et al., 2001).2.3.2. Data-driven processing of the RTA
Participants indicated the extent to which they were muddled/confused during the accident ona scale from 1 not muddled to 3 a lot.
2.3.3. Appraisal measuresThese measures were rated on a scale from 0 no to 3 yes, often. Negative interpretation of
intrusive memories was measured as the response to the question Do you ever think that some-thing is wrong with you because you cannot forget the accident, for example, do you ever feelyou are going mad?. Alienation from other people was measured as the response to the questionDo you feel like other people really dont understand what you went through?. As an indirectmeasure of appraisals relating to unfairness, children were asked to rate Do you get angry whenyou think about the accident?.
2.3.4. Maintaining cognitive strategiesThese measures were rated on a scale from 0 no to 3 yes, often. As in Ehlers, Mayou et
al. (1998), rumination was scored as the mean of two items. Participants rated whether they keptgoing over the accident over and over again and whether they kept thinking again and again aboutwhy the accident happened to them. Thought suppression was measured as the response to thequestion If pictures of the accident pop into your mind do you try to stop them and push themout of your mind again?. As a measure of persistent dissociation, three sy...