FACULTEIT DER MAATSCHAPPIJ- EN GEDRAGSWETENSCHAPPEN Graduate School of Childhood Development and Education
The effect of Eye Movement Desensitization and Reprocessing (EMDR) on complex
posttraumatic stress disorder and an intellectual disability
december 2012
Masterthesis Orthopedagogiek
Begeleider: mw. dr. H.R. Rodenburg
Tweede beoordelaar: dhr. dr. X.M.H. Moonen
Acknowledgement
It would not have been possible to write this thesis without the help and support of my supervisor, dr. H.R. Rodenburg. I also would like to thank my second supervisor, dr. X.M.H. Moonen, for his feedback and encouragement.
I am indebted to Kristal, centre for psychiatry and intellectual disability, and all my colleagues at Kristal Leiden and Gouda. Special thanks go out to E. Dautović and E.
Aldenkamp without whom I would not have started (nor finished) this project. I owe deepest gratitude to the patients of Kristal involved in this study, without their participation my thesis would not exist.
I am grateful towards V. de Wilde de Ligny and D. Timmer who provided me with statistical advice at times of critical need. Next, I would like to show my gratitude to dr. J. Veldman and N.Q.Crockett for their assistance in editing. Thanks also go out to all my friends for putting up with me, especially those who kept supporting and encouraging me; L. van der Meer; K. Leliveld; D. Elzenga; and K. de Jong. Special thanks goes to P. Streng for honesty at all times.
I must acknowledge L. Koppers for his patience, kindness and calmness. Words cannot express how important his support and love has been for me in finishing this thesis.
Last but not least, I would like to thank my parents and family for the support they provided me through my entire life, they receive my deepest gratitude and love for their dedication.
Abstract
Objective: The need for an effective treatment is vitally important because people with an intellectual disability are more vulnerable to develop complex posttraumatic stress disorder (C-PTSD) due to increased exposure to social and physical riskfactors. Research is lacking regarding effective treatment of C-PTSD and people with ID despite the overall positive effects of the use of Eye Movement Desensitization and Reprocessing (EMDR) in the non ID-population and in treatment of children. The main purpose of this study was to investigate the efficacy of EMDR on C-PTSD and an intellectual disability. The effect of EMDR on somatic complaints, anxiety symptoms and symptoms of depression was also investigated. Furthermore, the meditational effects of EMDR were explored.
Method: Patients at Kristal, Centre for Psychiatry and an intellectual disability in Leiden en Gouda were screened, after consented participating in this study. Patients were tested at four moments during the EMDR-treatment including a three months follow-up measurement. The results were compared to establish differences throughout the test-moments. The curves of PTSD-symptoms, somatic complaints, anxiety symptoms and symptoms of depression were graphically explored to establish plausible mediators.
Results: Reported PTSD-symptoms, somatic complaints and anxiety symptoms were significantly less at posttest compared to pre-test. The results were consistent at a three months follow-up-measurement. The results were not as clear concerning symptoms of depression as results differed across methods. Finally, anxiety symptoms might be a possible mediator of the effect of EMDR.
Conclusion: The results indicate that EMDR reduces symptoms of C-PTSD, somatic
complaints and anxiety symptoms in people with an intellectual disability. Further research is needed to confirm these significant results and establish anxiety symptoms as treatment mediator.
The effect of Eye Movement Desensitization and Reprocessing (EMDR) on complex
posttraumatic stress disorder and an intellectual disability
Intrusive thoughts of a traumatic event, avoidance of situations that remind an individual of the trauma, emotional numbing and physiological hyper arousal are symptoms of a posttraumatic stress disorder (PTSD). The prevalence of PTSD in the general population, based upon estimates in the United States vary between 5% and 10% (Kessler, Chiu, Demler, & Waters, 2005). Little information exists on the lifetime prevalence of traumatic events and PTSD in the general population in the Netherlands. De Vries and Olff (2009) selected a national representative sample of 1087 adults age 18 to 80 years using random digit dialing and surveyed by telephone using the Composite International Diagnostic Interview (CIDI) to determine the prevalence of trauma and PTSD. The found lifetime prevalence of any
potential traumatic event was 80.7%, and the found lifetime prevalence of PTSD was 7.4%. Women and younger people showed a higher risk at developing PTSD. It was concluded that PTSD is a fairly common disorder and exposure to traumatic events is high throughout the population.
PTSD was included in the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III, 1980) due to the effects of the Vietnam War on combat veterans. However, features of PTSD have been reported before that period and are currently referred to as Type I trauma’s (ten Broeke & de Jongh, 1997). Back then it was suggested that PTSD was also accurate when describing traumas such as abuse, incest and domestic abuse.
According to Herman (1992) the description of PTSD failed to capture characteristics created by prolonged abuse and abuse in sensitive developmental stages, now referred to as type II trauma’s ( Ten Broeke & de Jongh, 1997).
Herman (1992) suggested complex posttraumatic stress disorder (C-PTSD) to
describe the symptoms of long-term trauma. The ongoing negative impact of chronic repetitive trauma is more accurately described by complex posttraumatic stress disorder (C-PTSD) than it is by singular PTSD (van der Kolk, 2005). The pursuing symptoms, the loss of a sense of self and of dissociation are the most emphasized differentiations of C-PTSD from PTSD. A different name used to describe this cluster of symptoms is: Disorders of Extreme Stress Not Otherwise Specified (DESNOS; Ford, 1999). Because results from the DSM-IV Field Trials indicated that 92% of individuals with Complex PTSD/DESNOS also met criteria for PTSD, C-PTSD was not added as a separate diagnosis in the fourth version of the DSM (Roth, Newman, Pelcovitz, van der Kolk, & Mandel, 1997). This will be presumably still true for the DSM V.
Based upon Herman’s view (1992) the first requirement for the classification C-PTSD is that the individual must have experienced a prolonged period (months to years) of being controlled by another. The other subsequent criterion is alterations in emotional regulation. This may include persistent sadness, suicidal thoughts, explosive anger or inhibited anger. The third requirement is alterations in consciousness including forgetting traumatic events, reliving traumatic events or having episodes in which one feels detached from cognitive processes or body processes. Subsequent changes follow in self-perception such as helplessness, shame and guilt. Next come alterations in how the perpetrator is perceived. Examples include attributing power to the perpetrator or becoming preoccupied with revenge. Then there are changes in the relations to others, illustrated by worship of another person, distrust or a repeated search for a rescuer. The last requirement is related to changes in perception or a sense of hopelessness and despair.
People with an intellectual disability (ID) are more likely to develop any kind of mental health problems (Rutter, Graham & Yule, 1970; Emerson, 2003; Cooper, Smiley, Morrison Williamson & Allan, 2007). This includes the development of PTSD (Tharner,
2005; Ryan 1994). The prevalence of mental health problems is estimated to be two to four times higher than the prevalence of mental health problems in the non ID-population. This is due to the increased vulnerability to biological, psychological, and risk factors. The
interaction between these factors may account for the high rates of psychopathology (Cooper, Smiley, Morrison Williamson & Allan, 2007; Smiley, 2005; Whitaker & Read, 2006). Also early institutionalisation and co-morbid medical problems, next to the cognitive deficits, may increase vulnerability (Tomasulo & Razza, 2007). Even understanding oneself as being
disabled can be a traumatic event in itself (Hollins & Sinason, 2000; Levitas & Gilson, 2001). ID is defined as: ‘A disability characterized by significant limitations both in
intellectual functioning and in adaptive behavior as expressed in conceptual, social, and
practical adaptive skills. This disability originates before age 18 .”( Schalock,
Borthwick-Duffy, Bradley, Buntinx, Coulter, Craig et al., 2010). The categories of ID, as mentioned in the DSM IV-TR are: mild ID (IQ-score between 50-69) to profound ID (IQ-score below 25). Borderline of intellectual functioning starts at an IQ-score of 85 and ends at an IQ-score of 69.
The number of people in the Netherlands with borderline functioning is
approximately 300.000 to over 600.000 (CBZ, 2004). The estimated number of people with an IQ-score below 70 ranges from 55.000 persons to over tens of thousands more (Ras, Woitiez, Kempen & Sadiraj, 2010). The exact prevalence of the ID-population is difficult to establish due to additional criteria needed to establish the occurrence of an ID: next to certain IQ-scores, severe practical and social impairments and an onset age of younger than 18 complete the classification. Furthermore, when people don’t appeal upon social services or social welfare but function in general adequately with help from relatives and friends, they may not be noticed as having an intellectual disability at all.
Consequently, the exact prevalence of PTSD in the ID-population is also difficult to
establish and there is a lack of research and scientific literature regarding this subject. In a recent review of literature Mevissen and de Jongh (2011) found four articles reporting on incidence rates of PTSD in the ID-population with a total of 359 participants. The study of Ryan (1994, in Mevissen & de Jongh, 2011) which was the largest sample, reports a sample of 310 adults with moderate ID. In this study all participants had a history of trauma but 16% of the representative group (N = 51) met also the criteria for PTSD. Traumatic events in this sample included sexual abuse by multiple assailants (starting in childhood), physical abuse that was commonly the cause of the person’s intellectual disability, or life threatening neglect combined with some other active abuse or trauma (Ryan, 1994). This review did not
distinguish between PTSD and complex PTSD, but gave a sound summary of the content of traumatic events possible to occur in people with ID.
Considering the broad characteristics of C-PTSD there is a high possibility of co-morbidity. Keane, Marshall and Taft (2006) have obtained that at least a third up to 50 percent of people who suffer from PTSD also suffer from clinical depression. This is not surprising considering the overlap between symptoms of PTSD and depression: lack of interest, sleep problems, and difficulties concentrating.
Next to depression, generalized anxiety disorder can be developed in the aftermath of a life event (Green, Lindy, Grace, & Gleser, 1989; Kessler, Sonnega, Bromet, Hughes & Nelson, 1995; Franklin & Zimmerman, 2001). Participants of a study by Grant, Beck, Marques, Palyo and Clapp (2008) had all experienced type I trauma. In this study, PTSD , depression and generalized anxiety disorder were assessed with a combination of self-report and interview measures. The results of this study suggested that these were distinguishable but highly correlated disorders following a traumatic event. Because of this rather complex relationship, symptoms of anxiety and depression should also be taken into account when considering C-PTSD.
Only recently, due to the negative health effects of the first Gulf war and in the aftermath of the air crash in the Bijlmermeer in the Netherlands, research has increased its focus on (until then some incomprehensible) physical symptoms in survivors of disasters and major life-events. Veterans of the first Gulf war reported vague physical complaints such as headache, muscle ache, fatigue and difficulties in concentration, in the scientific literature known as the ‘Gulf war syndrome’. The cause of these somatic symptoms could not be fully physically explained. Schnurr and Green (2003) claimed mental problems to be the mediator in the relationship between traumatic stress and physical symptoms. Because survivors of natural disasters often respond with increasing physical symptoms, these symptoms are now considered part of an reaction on traumatic events. These physical complaints strongly correlate with functional defects and decreased quality of life (van den Berg, Grievink, van der Velden, Yzermans, Stellato, Lebret et al., 2008). In the study from Hurley (2008) the symptoms of depression in the ID-population were investigated and increased somatic complaints were found amongst other symptoms. Concerning the current study, it is important to take in consideration somatic complaints next to anxiety symptoms and symptoms of depression when focusing on C-PTSD.
Regarding the treatment for PTSD in people with ID there is a shortage of empirically proven methods of treatment for patients with PTSD and ID in contrast to
patients of the non-ID population . Mevissen and de Jong (2011) refer to this lack of research for treatment as ‘ treatment of patients with ID being still in its infancy’ and they draw the comparison with the findings of Prout and Nowak-Drabik (2003) who conducted a review stating that providing psychotherapeutic interventions for people with ID is considered most complicated. Having an intellectual disability is often used as an exclusion criterion for any kind of psychotherapy needed by a person with a lower developmental level and limited cognitive functioning.
In the non-ID population evidence-based treatments for PTSD are either Cognitive Behavior Therapy (CBT) or Eye Movement Desensitization and Reprocessing (EMDR). Bradley, Greene, Russ, Dutra & Westen (2005) concluded that EMDR is one of the most effective treatments for PTSD. Research by Seidler and Wagner supported with this findings by using a meta-analysis, they showed that EMDR is very effective (2006). Bisson, Ehlers, Mathews Pilling, Richardson and Turner (2007) concluded that EMDR was at least as effective as CBT.
Mevissen and de Jongh (2011) found four articles considering treatment of PTSD with patients with an ID. In two of these articles trauma focused CBT was applied but the results differed in effort and effect (Lemmon & Mizes, 2002; Stenfert Kroese & Thomas, 2006).
CBT is based upon insights of the cognitive and learning theories. In the treatment of PTSD, CBT is used to decrease negative emotions and behaviors, and to transform the
dysfunctional cognitions and attributions related to traumatic events and memories (Saunders, Berliner, & Hanson, 2004). Trauma-focused CBT consists of multiple components,
including: trauma narrative, in vivo mastery of trauma reminders, affect modulation, cognitive processing, psycho-education, relaxation, parenting skills, conjoint child-parent session, and enhancing safety, healthy sexuality, and future development (Cohen,
Mannarino, Perel & Staron, 2007). The number of sessions varies between 12 and 16. Methods of exposure are part of CBT applied for trauma. Saxe, MacDonald and Ellis (2007) reported that treatment with exposure-based techniques, such as flooding therapy (Saigh, Yule, & Inamdar, 1996) and gradual exposure (Cohen & Mannarino, 1993), seem to show substantial potential for treating children with PTSD symptoms (in: Rodenburg, Benjamin, Meijer & Jongeneel, 2009).
EMDR, the second recommended treatment for procedure for PTSD, is a relatively
new eight-phase treatment method to diminish traumatic symptoms. It is a psychotherapy that aims to resolve the development of trauma-related disorders in adults and was developed by Francine Shapiro in 1989. According to the theory, which is the basis for this treatment method, when a traumatic or distressing experience occurs, it may overwhelm usual cognitive and neurological coping mechanismsleaving patients inconvenienced. When applying
EMDR, the patient is asked to imagine what is still the most traumatic memory and is offered bilateral stimulation (either visual or auditory) at the same time. When the emotional level of disturbance has decreased and the functional cognitions about the trauma have
increased as by replacing the dysfunctional cognitions, the session can be stopped. Number of sessions may vary according to the type of traumatic event and severity of the
psychopathology (Shapiro, 2007 in : Rodenburg et al, 2009).
There are several advantages by using EMDR over other exposure techniques
according to van der Kolk (2002). These include the fact that it is easier to ‘dose’: a patient is asked to focus on the disturbing memory and endure the memory whilst following the offered stimulation with the eyes. This helps the patient to avoid extreme experiences of
physiological arousal which often accompanies exposure therapy. Another advantage according to van der Kolk (2002), is the identification of physical sensations instead of elaborate communication of the upsetting part of the traumatic event, therefore respecting privacy and avoiding feelings of shame.
A number of hypotheses to answer the question how EMDR causes its effect on PTSD has been suggested and examined. The decisive factor seems to be taxing the working memory with a dual task thereby reducing the memory in vividness and consolidate as less vivid and emotional (van den Hout & Engelhard, 2010). Engelhard (2010) provides the opposite U- method to explain why auditory bilateral stimulation doesn’t workin terms of the working memory hypothesis. Not taxing the working memory doesn’t change the recall,
neither does overtaxing it because this will put the emphasis on the dualtask instead of on the memory. The working memory has to be taxed just the right amount during the recall of an intrusive memory .
As EMDR relies little on cognitive and narrative capacities (capacities in which people with ID do not exceed) it could be the obvious method to treat PTSD in people with ID (Beer en de Roos, 2004). This statement can be supported by research conducted by Gunter and Bodner (2008, in van den Hout & Engelhard, 2010). The results of their study show that the capacity to multitask has a significant negative effect on the vividness of the memories. To be able to multitask one should have cognitive capacities such as selective attention and prolonged attention, causality, thinking, planning and metacognition. These capacities are very weak in people with an intellectual disability (van Nieuwenhuijzen, Orobio de Castro, van der Valk, Wijnroks, Vermeer & Matthys, 2006). Next, research by van der Kolk and Ducey (1989) has shown that traumatized people have a decreased capacity for analyzing and planning.
Another reason to apply EMDR on traumatized people and ID is that EMDR has been found to be effective on PTSD in the non-ID population (Bradley, Greene, Russ, Dutra, & Westen, 2005; Davidson & Parker, 2001; Seidler & Wagner, 2006; van Etten & Taylor 1998) and more recently to be effective in children and adolescents (Rodenburg et al., 2009; Ahmad, Larsson & Sundelin-Wahlsten, 2007). However, little research has been done to establish reliable and validity in instruments for assessing PTSD and C-PTSD in the ID population. Moreover, prevalence data and empirically proven evidence are limited concerning an effective treatment for people with ID and PTSD. To make a contribution to resolve this lack of research this study will describe a set of case-studies aiming on the effect of EMDR on C-PTSD and adults with an intellectual disability.
The main purpose of this study is to examine the effect of EMDR on C-PTSD using
the DSM IV/DM-ID as a tool of assessment. Next to the main goal of this study, the effect of EMDR on somatic complaints, anxiety symptoms and on symptoms of depression in people with an ID an C-PTSD will be examined.
Another aim of this study is to analyze how EMDR assumingly has a decreasing effect on these symptoms using a mediation analysis to examine treatment effect on PTSD-symptoms. Research to asses the impact of the supposed mediators somatic complaints, anxiety symptoms and symptoms of depression will be the second aim of this study. The hypothesis tested is that EMDR decreases trauma symptoms in adults with ID through a decrease of somatic complaints, anxiety symptoms and symptoms of depression.
Method
Procedure
A pilot study was started in the centre for Psychiatry and Intellectual Disability Kristal Leiden and Kristal Gouda in September 2010. EMDR was offered by six EMDR therapists who were trained by the EMDR Association in the Netherlands. They were assisted by two interns and one science practitioner. The interns and science practitioner helped the participants with the questionnaires and took care of the data.
At Kristal, EMDR is applied according to the manual composed by Shapiro (2007). The manual describes eight stages of equal importance. The therapist explains EMDR and analyses the history with each patient, so confirming the stability of the patient to cope with strong provoked emotions (history taking and preparation). By asking the patient to see the event as a short movie and focusing on the most disturbing and distressing image, the target of therapy is identified (assessment). By ranking this target on a scale from 1 to 10, the intensity of the target is captured in the Subjective Unit of Distress (SUD). Whilst holding this target in mind and concentrating on the arousing physical aspects, the patient is asked to follow the fingers of the therapist (or the taps produced by the therapist) moving from left to 11
right with his or her eyes (saccadic). Associations in thought that come into mind are asked to report briefly. The procedure is repeated until the original target is no longer disturbing (desensitization) and dysfunctional cognitions about the trauma have become functional (installation) (Shapiro, 2007). The patient is supported in performing a body scan to detect any physical distress. Hereafter the session is evaluated and closed.
Participants
A total of 133 participants was selected to participate in this study. All participants were patients of Kristal Leiden or Kristal Gouda and were assessed to fit in this therapy by a multidisciplinary team which included a certified psychiatrist. The inclusion-criteria were (1) either borderline intellectual functioning or mild ID according to the Diagnostic and
Statistical Manual of Mental Disorders (DSM-IV-TR), (2) diagnosed with C-PTSD, (3) age above 18 and (4) a proper understanding of the Dutch language.
Graph 1. The screened sample
Of the included 133 patients , 67 were diagnosed with either PTSD or C-PTSD. Only 26 patients were eventually included in the study due to several factors such as insufficient compliance. Of these 26 participants, 22 were diagnosed with C-PTSD. Currently, nine patients have completed the treatment and two are waiting to complete the follow up
measurement. These 11 participants will be in the focus of this study. The characteristics can be read in table 1. INCLUDED N = 133 PTSD N = 67 PARTICIPANTS N = 26 PTSD N = 4 C-PTSD N = 22 PRE-TREATMENT N = 8 EMDR-TREATMENT N = 3 AWAITING follow -up N = 2 COMPLETED TREATMENT N = 9 DROPPED OUT N = 41 NO PTSD N = 46 DROPPED OUT N = 20 12
Table 1. Characteristics of the 11 patients included in the Kristal EMDR study Demographics Percentages Gender Male 9,1 female 90,9 Co-morbidity Yes 63,4 no 36,6
Material status Single 18,2
Divorced 36,4
missing 45,5
Education Special needs elementary school 9,1
Secondary special needs education 18,2 Practice-based education 9,1
Regular education 9,1
Missing 45,5
Employment Part-time, social services 9,1
Fulltime social services 18,2
Part-time regular job 9,1
Social welfare 9,1 Unemployment 9,1 Missing 45,5 Origin Dutch 45,5 other 9,1 missing 45,5
The age of the participants ranges between 18 en 55 and their intellectual functioning (full IQ) assessed with a valid IQ test ranges between 57 and 83 ( M = 67,50, SD = 8,91). Six patients have a mild ID an four patients are borderline functioning. Of one participant the level of intellectual functioning could not be established because the discrepancy between verbal and performal IQ was too large to make a reliable statement about the total IQ-score. The level of education ranges between special needs elementary school and secondary regular education. One of the participants was unemployed and one participant had a regular part-time job. The other participants were employed within social services or depended on social welfare. Only one participant wasn’t of Dutch origin. Co-morbid psychiatric disorders were diagnosed in seven out of the 11 patients. A co-morbid personality disorder was diagnosed in five patients, co morbid depression in one and two participants had severe problems in relationships.
Design
The study is set up as a series of case studies (as described by Drotar in 2009; 2010) for lay-out see table 2 (in: Dautovic 2011, manuscript in preparation).
Table 2. Screening
Intake T0: Baseline T1: Pretest Pretreatment T2: Pretest T3: Posttest T4: Follow-up Intake session with a therapist Questionnaires ± 3 months before treatment Questionnaires ± 1 week before pre-treatment Stabilizing treatment Questionnaires ± 1 week before EMDR treatment Questionnaires ± 1 week after treatment closure Questionnaires ± 3 months after treatment closure
Using case-series in research serves several important purposes, including examining underrepresented topic areas. It is imperative for exploring new clinical populations, needs and challenges but it also stimulates development of new intervention models and
frameworks. Regarding EMDR case series can illustrate clinical effectiveness of new interventions delivered in practice, for instance special populations such as people with an ID. Case serie-studies may help to transfer the use of empirically supported interventions to clinical practice (Drotar, 2009). Flyvbjerg (2006, p. 219) states “A scientific discipline
without a large number of thoroughly executed case studies is a discipline without systematic
production of exemplars, and a discipline without exemplars is an ineffective one. Social
science may be strengthened by the execution of a greater number of good case studies.”
In this study patients of Kristal have an intake session with a therapist and before starting treatment are thoroughly examined diagnostically. If after this diagnostic research a patient is diagnosed with PTSD, he or she will be informed about the purpose of this study, and is asked whether he or she would like to participate in the study, and if so is asked for signing an informed consent form. They then enter the treatment trial and they are asked, before and after EMDR treatment, to fill in several questionnaires regarding PTSD, somatic complaints, anxiety and depression. Patients with complex PTSD are often offered a
stabilizing pretreatment before EMDR, in order to be able to cope with emotions provoked trough subsequent EMDR treatment.
Measures
To asses the symptoms of post traumatic stress disorder as stated in the DSM IV, the patients completed either the ‘Impact of Event Scale-revised’ (IES-R) (Weiss & Marmar, 2004) (Horowitz, Wilner and Alvarez, 1979) or the Dutch translation of this questionnaire: the Schokverwerkingslijst (SVL-22, Brom & Kleber, 1985; Kleber & de Jong, 1998). Internal validity of the IES-R subscales was good. The later added ‘Hyperarousal Scale (Weiss & Marmar, 2004) has good predictive validity regarding assessing trauma.
A study of Mooren and Kleber (2001) didn’t support the validity of the ‘Hyperarousal Scale’ in the SVL-22 but other studies show a correlation with the Dutch version of the Posttraumatic Stress Symptom Scale-Self Report which was validated as good (van der Hart, Kleber, Olde & Pop, 2006). Studies differ in the assessment of the cut-off scores regarding PTSD. In some studies a minimal score of 26 is suggested (Kleber et al., 1992) in others a cut-off score of 30 suggested (Blanchard &Hickling, 1997; Bryant &Harvey, 1996). Nevertheless, the SVL-22 is considered to be of psychometrical good quality (van der Hart, Kleber, Olde & Pop, 2006). In the current study the total score of the SVL-22 instead of the dimensions, is used to illustrate and analyze PTSD-symptoms. A cut-off score of 33 is used because this is automatically arranged by the used software for online professional research. A certified psychiatrist validated the diagnoses of C-PTSD.
Both the IES-R and the SVL-22 use a 5 point Likert-scale type to asses whether patients experienced symptoms of avoidance, re-experience and/of hyperarousal in the past seven days that could be attributed to an enduring life event. Questions ( asked in Dutch but translated in English) are ‘I tried to vanish the event out of my memory’ and ‘Other issues kept reminding me of the event’. The scale ranges from (0) ‘not at all’, (1)’rarely’, (2) ‘sometimes’, (3) ‘often’ and (4) ‘very often’.
To asses levels of somatic complaints, depression and anxiety, the Dutch translation
of the Brief Symptom Inventory (BSI) (Derogatis, 1983) was used. This is a condensed version of the Symptom Checklist-90-R (SCL-90-R) (Derogatis & Melisaratos, 1976) and consist of 53 items covering nine dimensions of psychopathology. Every item states a symptom of psychopathology. An example from the dimension depression is ‘Loneliness, even when you’re in company’ whereas ‘Lightheadedness or problems controlling your balance’ is a item belonging to the dimension somatic complaints. The 5 point Likert scale is used to rank the items in weight of burden in the past seven days from (0) ‘not at all’, (1) a little, (2) ‘quite’, (3) ‘a lot’ to (4) ‘extremely’. De Beurs and Zitman (2006) translated the BSI in Dutch and Wieland, Wardenaar, Fontein and Zitman, (2012) validated the BSI for the use with people with an intellectual disability. De Beurs &Zitman concluded ‘The BSI is an
excellent screener for psychopathology and a good general outcome measure’ (in Wieland et
al., 2012, p.845).
Statistical Analysis
Although all instruments are reported to have good psychometric quality, it seemed appropriate to conduct the reliability score for the instruments regarding the patients of Kristal. The scores from the pre-test were used; the reliability ranges from good to excellent and is displayed in table 3. The scores are in accordance with given reliability by former studies (Wieland et al., 2012).
Table 3. Reliability of the IES-R, SVL-22 and subscales somatic complaints, anxiety symptoms, and symptoms of depression of the BSI at pretest
IES-R SVL-22 BSI Somatic Complaints BSI Anxiety Symptoms BSI Symptoms of Depression Crohnbach’s Alpha .83 .95 .88 .82 .76
The purpose of this study was to examine the efficacy of applying EMDR on adults with C-PTSD and an intellectual disability. A paired t-test was used to establish a statistically significant difference between the results of the pre-test on the SVL-22 and the results of a
post-test on a .05- significance level. If EMDR indeed is effective for adults with C-PTSD and an intellectual disability the scores on the posttest will be lower than the prior results of the SVL-22. To asses for long-term effects no significant difference between the posttest and the follow-up is to be expected, as this will represent the consistency of the effects obtained. Because of the small sample size, an additional Wilcoxon signed rank test is conducted to reduce Type II error.
The next aim of this study was to examine whether EMDR was effective to diminish symptoms correlated with somatic complaints, anxiety symptoms, and symptoms of
depression. A paired sample t-test is conducted to account for a statistical significance between the results obtained at pre-test and the post-test and is confirmed by applying a Wilcoxon signed rank test.
In order to examine the treatment mediators of EMDR-treatment the symptoms of post traumatic stress, somatic complaints, depression and anxiety are graphically exposed. These assumed mediators in treatment are ‘mechanisms or processes through which a
treatment might achieve its effects’(Kraemer et al. 2002 p.878, in Maric, Wiers & Prins,
2012). Identifying this mechanisms contributes to the improvement of treatments because it allows to identify the effective treatment components. Maric et al. (2012) give two reasons why mediation analysis can be useful in a single case experimental design. First, the mediators of newly developed treatments can be investigated on a small scale prior to
investigation in randomized clinical trials. Second, applying single-case experimental designs involve the possibility of capturing multiple mechanisms which are likely to be related to an individual’s functioning (MacKinnon, 2008, in Maric et al., 2012).
According to Baron and Kenny (1986), four conditions have to be met when investigating the mediation of treatment outcome: (1) the treatment needs to affect the treatment outcome, (2) the treatment condition should predict changes in the mediator, (3)
while controlling for the treatment, change in the mediator should be significantly associated with change in the treatment outcome and (4) when change in the mediator is statistically controlled for, the effect of treatment on change in treatment outcome is attenuated. The method is best comprehensible by assuming a triangle, considering X (the independent variable) to be in the left corner, Y (the dependent variable) in the right corner and the mediator in the middle above.
Me
Path a Path b
X Y
Path c
MacKinnon (2008, in Maric et al., 2012) found the most important conditions for mediation to be the paths from X to the mediator (path a) and from the mediator to Y ( path b). This so called product of co-efficient test is then divided by the standard error of the product and compared to a normal population distribution to test for significance.
Next to graphically exposing possible mediators, MacKinnons approach is applied in this study to interpret the mediating effect if the first step is a non-significant one. First, the effect of the trauma symptoms at pre-test (X) on the trauma symptoms at post-test (Y) is established (path c). Hereafter, with MacKinnons statement in mind, the effect of the trauma symptoms at pre-test (X) on the decrease in pathological dimensions (Me; path a) was established followed by the effect of the decreasing dimensions (Me) on trauma symptoms at post-test (Y; path b).
Results
Does EMDR have an effect on people with C-PTSD and an intellectual disability?
A paired t-test was used and results showed a statistically significant effect. These results were stable over three months time because no significant result was found comparing
the posttest-outcome with the outcome at follow-up. The results were confirmed by applying the Wilcoxon signed rank test which at the same time gave information about the direction of change by ranking: all patients involved showed lower scores at post-test. The results are displayed in table 4.
Does EMDR have an effect on somatic complaints, anxiety symptoms and symptoms of
depression on people with C-PTSD and an intellectual disability?
The same methodology was used to examine the effect of treatment on the three psychopathology dimensions mentioned. The results of the posttest differed statistically significant on the dimensions somatic complaints and anxiety symptoms. Symptoms of depression were significantly diminished using the t-test but this finding was not supported by applying the Wilcoxon signed rank test. The consistency of these findings is stable in the follow up condition but considering the insignificant result regarding symptoms of
depression, this is less meaningful concerning this dimension (table 4).
Table 4. Paired t-test and Wilcoxon signed rank test results
t-test Wilcoxon signed rank test
Pretest-posttest Posttest-follow up Pretest-posttest Posttest-follow up PTSD-symptoms Somatic complaints Anxiety symptoms Symptoms of depression .000* .001* .005* .032* .362 .942 .627 .878 .005* .003* .010* .061 .310 .866 .932 .786 *α = .05
Is the effect of EMDR mediated by a decrease in somatic complaints, anxiety symptoms
and/or symptoms of depression?
The paths of the means of somatic complaints, anxiety symptoms and symptoms of depression over the complete treatment-program of EMDR, are shown in graph 2.
Graph 2. Development of psychiatric symptoms during EMDR-treatment (N = 11)
The levels of anxiety and of depression increases during pre-treatment whereas somatic complaints decrease. Focusing on the EMDR-treatment which is applied between the T2 and T3 all show a decrease in the psychiatric dimensions decrease. However, anxiety seems to make the largest downfall from the pre-treatment measured on T1 to the
posttest-measurement on T2. The curves of somatic complaints and depression seem to vary more in the course of the treatment. To estimate a potential mediator the curves must precede the changes of the curve of the post-traumatic symptoms as measured on the IES-R and SVL-22. A second graph was plotted to explore the relationship between the curves of traumatic symptoms and the three dimensions. Because the questionnaires differed in size, all scores are converted into percentages representing the means of the symptoms of the patients (graph 3).
Graph 3. Mean Percentages of Psychopathology Dimensions and PTSD symptoms (N = 11)
0 5 10 15 20 T0 T1 T2 T3 T4 Results BSI Measurement
Somatic Complaints Symptoms of Depression Anxiety symptoms
The percentage-curves all show a decrease after T2 representing a significant change, as confirmed by applying a t-test. Interesting are the more or less equal curves of PTSD-symptoms and anxiety PTSD-symptoms. Both curves are at their highest peak at T1 to decrease more than the other curves towards T3. Anxiety symptoms seem to drop earlier, the decreasing begins in the pre-treatment phase preceding the decrease of PTSD-symptoms supporting the assumption of functioning as a mediator. The percentages of each
measurement can be found in table 5.
Table 5. Percentages of the mean of results on the BSI and IES-R or SVL-22
Measurement PTSD-symptoms
Somatic Complaints
Symptoms of
Depression Anxiety symptoms
T0 50,3% 36,6% 32,1% 45%
T1 64,4% 27,5% 45,8% 71,1%
T2 59,7% 43,6% 38,3% 50%
T3 12,2% 16,8% 20,8% 13,3%
T4 26,9% 20,5% 17,2% 16,7%
To establish whether the anxiety symptoms are a mediator in the effect of EMDR the products of coefficient of the decrease in the dimensions of pathology and the outcome on the post-test were calculated as explained above. Although no significant result was found
regarding path c, nor was their a significant result regarding path a, the reduction of anxiety symptoms in the downfall simultaneously with the downfall of the curve for PTSD-symptoms is significantly correlated to the post-test score of PTSD-symptoms (path b). No significant results were found regarding somatic complaints or symptoms of depression. Nevertheless,
0 10 20 30 40 50 60 70 80 T0 T1 T2 T3 T4 Percentage Measurement
PTSD-symptoms Somatic Complaints Symptoms of Depression Anxietysymptoms
the significant effect of the decrease of anxiety symptoms is interesting and worthwhile mentioning yet there is not enough statistical evidence to support the claim of anxiety symptoms functioning as a mediator (table 6).
Table 6. Results of Mediation analysis
Y Path a X Me Path b Me Y Predictors B SE β t p B SE β t p B SE β t p X: PRE .257 .240 .353 1.068 .317 Me: SOM -.070 .106 -.216 -.663 .524 .745 .758 .328 .984 .354 Me: ANX -.179 .123 -.438 -1.461 .178 1.226 .454 .690 2.699 .027* Me: DEPR -.102 .106 -.304 -.958 .363 1.114 .710 .485 1.570 .155 Me = mediator; PRE= pretest trauma symptoms; SOM = posttest – pretest somatic complaints; ANX = posttest – pretest anxiety symptoms; DEPR = posttest-pretest symptoms of depression; Y = posttest trauma symptoms
* α = .05
Discussion
The main purpose of this study was to search for efficacy of EMDR on patients with C-PTSD and an intellectual disability using a series of case studies design. Also the effect of EMDR on somatic complaints, anxiety symptoms and symptoms of depression in people diagnosed with C-PTSD and an intellectual disability was investigated. Additionally mediators were examined for their effect of EMDR on C-PTSD at posttest, using somatic complaints, anxiety symptoms and, symptoms of depression as possible mediators.
In line with expectations based upon studies concerning the non –ID-population the results were overall positive. A significant difference was found in the sample concerning PTSD-symptoms at time of pretest and posttest assessment. The direction of the difference was as expected: at posttest, patients reported significantly less symptoms.
Additionally, somatic complaints and anxiety symptoms were also significantly diminished at posttest. All results found were stable as shown in the three months follow-up measurement.
Differences in effect on symptoms of depression were less clear because the results differed when applying different statistical analyses. Using the Wilcoxon signed rank test 3
out of 11 participants reported more symptoms of depression which was in contrast with the significant result found by applying the t-test. One of these patients suffered from a co morbid depression and although this patient reported a decrease in PTSD-symptoms, an additional therapy was offered to him to cope with the depression. Another patient suffered from a borderline personality disorder and had recently broken with family which could have established an effect on the self reported depression symptoms. The third patient wasn’t diagnosed with a co morbid disorder but gave no further explanation. Further research should be done to answer the question whether EMDR has an effect on symptoms of depression in people with an intellectual disability. However, an intellectual disability in general can account for incapability to cope with stressful life-events (Hartley & Maclean, 2010).
The third purpose of this study was to establish treatment mediators by conducting a mediation analysis. Mediators were obtained by inspecting and analyzing a graphic
representation of the curves of PTSD-symptoms and three psychopathological dimensions mentioned in this study. Because both somatic complaints and symptoms of depression followed a more diversified path than the obvious downfall of the curves representing PTSD-symptoms and anxiety PTSD-symptoms, the only plausible mediator found in this study was the decrease in symptoms of anxiety. This result found is partial confirmed by the significant effect of the decrease in anxiety symptoms on trauma symptoms at posttest. This result is rather likely considering PTSD (and C-PTSD) is an anxiety disorder developed after being exposed to a possibly traumatic event. Therefore anxiety symptoms should be given consideration when applying EMDR as a treatment for C-PTSD in people with an ID.
Maric et al. (2012) presented several sound methods applying mediation analysis in therapy research. In this study the method suggested by MacKinnon (2002, in Maric et al., 2012) was applied even though the sample size in this study was too small to guarantee results to be generalized. Also it did not have the appropriateness considering the design of
research to detect mediators supported by a statistical method. However, the mere downfall of symptoms of anxiety graphically exposed, gives a fair idea of the direction of assessment of plausible mediators in further research.
The failed support in results of statistical analysis concerning mediators is likely due to the small sample size (N = 11). This is due to high dropout related to therapeutic
incompliance, to patients being assigned to a different kind of therapy or to therapists evaluating further participation of their patient as not being in their best interest. However, this small sample size is not unusual in clinical single subject research (Rapoff & Stark, 2008) and pilot studies such as this study, cannot be used to generalize results to the whole population of people with C-PTSD and an intellectual disability. In future research this sample should be enlarged to increase the possibility of generalization of significant results. Another weakness of this study is the absence of a control group which makes it impossible to compare this treatment to a well established control condition.
There are a few issues regarding the content of this study. Martorell and Takanikos (2008) stress the importance of the difference between negative life-events and traumatic events. There’s no evidence which demonstrates conclusively the distinction between negative life events and traumatic experiences (other than the development of PTSD/C-PTSD). Because of the deficit of empirical research regarding this unclear distinction, research should focus more on the role of negative life events and their development into traumatic experiences.
Next, the used questionnaires, SVL-22 (Brom & Kleber, 1985; Kleber & de Jong, 1998) and the IES-R (Weiss & Marmar, 2004) are assumed to be able to detect symptoms of PTSD rather than symptoms of C-PTSD. As stated earlier the ongoing negative impact of chronic repetitive trauma is more accurately described by complex posttraumatic stress disorder (C-PTSD) than it is by PTSD alone (Herman, 1992). Due to the unavailability (so
far) of a questionnaire capturing the symptoms of C-PTSD this study was executed using instruments measuring PTSD-symptoms which were of good psychometric quality. One must take into consideration that according to van der Kolk (2001) PTSD has become the central diagnosis for traumatized patients but it does not take into account the complexity of adaption to complex traumatization.
This study generates new hypothesizes regarding C-PTSD in people with an intellectual disability while simultaneously contributing to resolving the lack of research regarding this subject. It also points to the difference made by Herman (1992) of PTSD and C-PTSD which is rarely made in scientific literature and in research. Despite its limitations the current study indicates that the use of EMDR has positive effects in treatment of C-PTSD in people with an intellectual disability but further research is necessary to generalize this assumption to the whole population. Furthermore, treatment mediators in EMDR should be more accurately investigated to find more evidence for the question how positive EMDR treatment effects are established, herewith increasing benefits for the patients involved.
Since EMDR doesn’t require many therapeutical sessions or excessive verbal communication about every detail of an traumatic event, professionals should take into account using EMDR by patients with C-PTSD (and PTSD) and an intellectual disability.
References
Ahmad, A., Larsson, B., & Sundelin-Wahlsten, V. (2007). EMDR treatment for children with PTSD: Results of a randomized controlled trial. Nordic journal of psychiatry, 61(5), 349-354.
American Psychiatric Association (2000). Diagnostic and statistical manual of mental
disorders (DSM-IV-TR). Washington DC: American Psychiatric Association.
Baron, R. M., & Kenny, D. A. (1986). The moderator-mediator variable distinction in social psychological research: Conceptual, strategic, and statistical considerations. Journal of Personality and Social Psychology, 51, 1173–1182.
Bisson, J. I., Ehlers, A., Matthews, R., Pilling, S., Richards, D., & Turner, S. (2007).
Psychological treatments for chronic post-traumatic stress disorder: Systematic review and meta-analysis. British Journal of Psychiatry, 190, 97-104.
Bradley, R., Greene, J., Russ, E., Dutra, L., & Westen, D. (2005). A multidimensional meta-analysis of psychotherapy for PTSD. The American Journal of Psychiatry, 162, 214-227.
Brom, D., & Kleber, R. J. (1985). De Schok Verwerkings Lijst. Nederlands Tijdschrift voor
de Psychologie, 40, 164-168.
Bryant, R. A., & Harvey, A. G. (1996). Posttraumatic stress reactions in volunteer firefighters. Journal of Traumatic Stress, 9(1), 51-62.
Buntinx, W.H.E.( 2003). Wat is een verstandelijke handicap? Definitie, assessment en
ondersteuning volgens het AAMR-model, AAMR-model van verstandelijke handicap
In: Nederlands Tijdschrift voor de Zorg aan mensen met een verstandelijke beperking, Koninklijke Van Gorcum.
Broeke, E. ten, & Jongh, A. de. (1997). EMDR bij de behandeling van Type II psychotrauma: een casus. Tijdschrift voor psychiatrie, 39, 249-255.
CBZ, College Bouw Ziekenhuisvoorzieningen (2004). Licht Verstandelijk Gehandicapte
jongeren met probleemgedrag – signaleringsrapport. Utrecht, CBZ.
Cohen, J. A., & Mannarino, A. P. (1993). A treatment model for sexually abused preschoolers. Journal of Interpersonal Violence, 8, 115 131.
Cohen, J. A., Mannarino, A. P., Perel, J. M., & Staron, V. (2007). A pilot randomized controlled trial of combined trauma-focused CBT and setraline for childhood PSTD symptoms. Journal of the American Academy of Child and Adolescent Psychiatry, 46
(7 ), 811-819.
Cooper, S.A. , Smiley, E., Morrison, J., Williamson, A., Allan L.(2007) Mental ill-health in adults with intellectual disabilities: Prevalence and associated factors. British Journal
of Psychiatry, 190, pp. 27–35.
Dautovic, E., Rodenburg, H. R., Aldenkamp, E., & Plat, M. M. C.(2011). EMDR effectiveness in adults with PTSD and intellectual disability: A case series (manuscript in preparation).
Davidson, P. R., Parker, K. C. H. (2001). Eye movement desensitization and reprocessing
(EMDR): A meta-analysis. Journal of Consulting and Clinical psychology, 69, 305-316.
De Beurs, E., & Zitman, F. G. (2006). De Brief Symptom Inventory (BSI). De betrouwbaarheid en validiteit van een handzaam alternatief voor de SCL-90.Maandblad Geestelijke Volksgezondheid, 61(2), 120.
De Vries, G. J., & Olff, M. (2009). The lifetime prevalence of traumatic events and
posttraumatic stress disorder in the Netherlands. Journal of traumatic stress, 22(4), 259-267.
Derogatis, L. R., Rickels, K., & Rock, A. F. (1976). The SCL-90 and the MMPI: A step in the validation of a new self-report scale. The British Journal of Psychiatry, 128(3), 280-289.
Derogatis, L. R., & Melisaratos, N. (1983). The Brief Symptom Inventory: an introductory report. Psychological medicine, 3, 595-605.
Drotar, D. (2009). Case studies and series: A call for action and invitation for submission.
Journal of Pediatric Psychology, 34, 795-802.
Emerson E. (2003). Prevalence of psychiatric disorders in children and adolescents with and without intellectual disability. Journal of Intellectual Disabilities Research, 47, 51–8. Engelhard, I. M., van Uijen, S. L., & van den Hout, M. A. (2010). The impact of taxing
working memory on negative and positive memories. European Journal of
Psychotraumatology, 1.
Etten, M. L. van, & Taylor, S. (1998). Comparative efficacy of treatments for post-traumatic stress disorder: A meta-analysis, Clinical Psychology and Psychotherapy, 5, 126-144.
Ford, J. D. (1999). Disorders of extreme stress following war-zone military trauma. Journal of Consulting and Clinical Psychology, 67, 3-12.
Flyvbjerg, B. (2006). Five misunderstandings about case-study research.Qualitative
inquiry, 12(2), 219-245.
Franklin, C. L., & Zimmerman, M. (2001). Posttraumatic stress disorder and major depressive disorder: Investigating the role of overlapping symptoms in diagnostic comorbidity. The Journal of nervous and mental disease, 189(8), 548-551.
Grant, D. M., Beck, J. G., Marques, L., Palyo, S. A., & Clapp, J. D. (2008). The structure of distress following trauma: Posttraumatic stress disorder, major depressive disorder, and generalized anxiety disorder. Journal of Abnormal Psychology, 117(3), 662.
Green, B. L., Lindy, J. D., Grace, M. C., & Gleser, G. C. (1989). Multiple diagnosis in posttraumatic stress disorder: The role of war stressors. Journal of Nervous and
Mental Disease; Journal of Nervous and Mental Disease.
Gunter, R. W., & Bodner, G. E. (2008). How eye movements affect unpleasant memories: Support for a working-memory account. Bahaviour Research and Therapy, 46, 913-931.
Hart, O. van der, Kleber, R. J., Olde, E., & Pop, V. J. M. (2006). Childbirth and Posttraumatic Stress Responses: A validation study of the Dutch Impact of Event Scale – Revised.
European Journal of Psychological Assessment, 22, 259-267.
Herman, J. L. (1992). Complex PTSD: A Syndrome in Survivors of Prolonged and Repeated Trauma. Journal of Traumatic Stress, 5, 377-391.
Hickling, E.J. Blanchard, E. B. (1997) The private practice psychologist and manual-based treatments: a case study in the treatment of post-traumatic stress disorder secondary to motor vehicle accidents. Behaviour Research and Therapy, 35 (1997), pp. 191–203. Hollins, S., Sinason V. (2000) Psychotherapy, learning disabilities and trauma: New
perspectives British Journal of Psychiatry, 176, pp. 32–36.
Horowitz, M., Wilner, N.J., & Alvarez, W. (1979). Impact of events scale: A measure of subjective stress. Psychosomatic Medicine, 41, 209-218.
Hurley, A. D. (2008). Depression in adults with intellectual disability: symptoms and challenging behaviour. Journal of Intellectual Disability Research, 52(11), 905-916. Jong, E. de, & Kleber, R. J. (1998). Dutch version of the Impact of Event Scale—Revised.
Internal report. Utrecht: Department of Clinical Psychology, Utrecht University. Keane, T. M., Marshall, A. D., & Taft, C. T. (2006). Posttraumatic stress disorder: etiology,
epidemiology, and treatment outcome. Annual Review of Clinical Psychology, 2, 161-197.
Kessler, R. C., Sonnega, A., Bromet, E., Hughes, M., & Nelson, C. B. (1995). Posttraumatic stress disorder in the National Comorbidity Survey. Archives of general
psychiatry, 52(12), 1048.
Kessler, Chiu, Demler, Waters (2005) Prevalence, severity, and comorbidity of 12-month DSM IV disorders in the national comorbidity survey replication Archives of General
Psychiatry, 62 (2005), pp. 617–627.
Kraemer, H. C., Wilson, G. T., Fairburn, C. G., & Agras, W. S. (2002). Mediators and moderators of treatment effects in randomized clinical trials. Archives of General
Psychiatry, 59, 877–883.
Lemmon V. A., & Mizes J. S. (2002). Effectiveness of exposure therapy: a case study of posttraumatic stress disorder and mental retardation. Cognitive Behavioral Practice,
9, 317–23.
Levitas, A.S., Gilson, S.F. (2001) Predictable crises in the lives of people with mental retardation. Mental Health Aspects of Developmental Disabilities, 3, pp. 89–100. MacKinnon, D. P. (2008). Introduction to statistical mediation analysis. Mahwah, NJ:
Erlbaum.
Maric, M., Wiers, R. W., & Prins, P. J. (2012). Ten Ways to Improve the Use of Statistical Mediation Analysis in the Practice of Child and Adolescent Treatment
Research. Clinical child and family psychology review, 1-15
Martorell, A., Tsakanikos, E. (2008) Traumatic experiences and life events in people with intellectual disability. Current Opinion in Psychiatry, 5, pp. 445–448.
Mevissen, L., & De Jongh, A. (2010). PTSD and its treatment in people with intellectual disabilities: A review of the literature. Clinical Psychology Review,30(3), 308-316. Mooren, G. T. M., & Kleber, R. J. (2001). Construct validity of the Impact of Event Scale: An empirical test among Bosnian samples. In: G. T. M. Mooren (Ed), The impact of
war: Studies on the psychological consequences of war and migration, pp. 25-47.
Delft: Eburon.
Nieuwenhuijzen, M. van, Orobio de Castro, B., Valk, I. van der, Wijnroks, L., Vermeer, A. and Matthys, W. (2006). Do social information-processing models explain aggressive behaviour by children with mild intellectual disabilities in residential care? Journal of
Intellectual Disability Research, 50(11), 801-812.
Roth, S., Newman, E., Pelcovitz, D., van der Kolk, B. and Mandel, F. S. (1997), Complex PTSD in victims exposed to sexual and physical abuse: Results from the DSM-IV field trial for posttraumatic stress disorder. Journal of Traumatic Stress, 10: 539–555. Prout, T.H., Nowak-Drabik, K.M. (2003) Psychotherapy with persons who have intellectual
disabilities: An evaluation of effectiveness. American Journal on Intellectual
Disabilities, 108, pp. 82–93.
Rapoff, M. A., & Stark, L. (2008). Journal of pediatric psychology statement of purpose: section on single-subject studies, Journal of Pediatric Psychology, 33, 16-21. Rutter, M, Graham, P., & Yule, W. (1970). A neuropsychiatric study in childhood.
Philadelphia: Lippincott.
Rodenburg, R., Benjamin, A., Roos, de, C., Meijer, A. M., & Stams, G. J. (2009). Efficacy of EMDR in children: A meta-analysis. Clinical Psychology Review, 29, 599–606. Roos, C. de, Beer, R. (2003). EMDR bij kinderen en adolescenten: de klinische praktijk.
Kind en Adolescent Praktijk, 2, 12-18.
Ryan, R. (1994). Posttraumatic stress disorder in persons with developmental disabilities.
Community Mental Health Journal, 30, 45-54.
Saunders, B. E., Berliner, L., & Hanson, R. F. (2004). Child physical and sexual abuse:
Guidelines for treatment. Charleston: National Crime Victims Research and
Treatment Center.
Schalock, R.L., Borthwick-Duffy, S.A., Bradley, V.J., Buntinx, W.H.E., Coulter, D.L., Craig, E.M., et al., (2010). Intellectual Disability: Definition, Classification, and Systems of
Supports (Eleventh edition). Washington DC: AAIDD.
Saigh, P. A., Yule, W., & Inamdar, S. C. (1996). Imaginal flooding of traumatized children and adolescents. Journal of School Psychology, 34(2), 163-183.
Saxe, G. N., MacDonald, H. Z., & Ellis, B. H. (2007). Psychosocial approaches for children with PTSD. In M. J. friedman, T. M. Keane & P. A. Resick (Eds.), Handbook of
PTSD: Science and practice (pp. 359-375). New York: The Guilford Press.
Schnurr, P. P., & Green, B. L. (Eds.). (2003). Trauma and health: Physical health consequences of exposure to extreme stress.Washington, DC: American Psychological Association.
Seidler, G. H., & Wagner, F. (2006). Comparing the efficacy of EMDR and trauma-focused cognitive-behavioral therapy in the treatment of PTSD: a meta-analytic study.
Psychological Medicine, 36, 1515–1522.
Shapiro, F. (2001). Eye movement and desensitization and reprocessing: Basic principles,
protocols and procedures. New York: Guilford Publications.
Shapiro, F., & Forrest, M. S. (2005). EMDR: Vernieuwende therapie tegen angst, stress en
trauma. Antwerpen: Garant.
Shapiro, F. (2007). EMDR and case conceptualization from an adaptive information
processing perspective. In L. Maxfield, F. Shapiro & F. W. Kaslow (Eds.), Handbook
of EMDR and family therapy processes (pp. 3-34). Hoboken, NJ: John Wiley & Sons
Inc.
Smiley, E. (2005). Epidemiology of mental health problems in adults with learning disability: an update. Advances in Psychiatric Treatment, 11(3), 214-222.
Stenfert Kroese, B., Thomas, G. (2006) Treating chronic nightmares of sexual assault survivors with an intellectual disability—Two descriptive case studies. Journal of
Applied Research in Intellectual Disabilities, 19, pp. 75–80.
Tharner, G. (2005). Over de toepassing van EDMR bij de behandeling van mensen met een lichte verstandelijke beperking. In R. Didden (red.). In perspectief.
Gedragsproblemen, psychiatrische stoornissen en lichte verstandelijke beperking. (pp
145-168). Houten: Bohn Stafleu van Loghum.
Tomasulo, D.J., Razza, N.J. (2007) Posttraumatic stress disorder in Fletcher, Loschen, Stavrakaki, First (Eds.), Diagnostic Manual-Intellectual Disability (DM-ID): A textbook of diagnosis of mental disorders in persons with intellectual disability, NADD Press, Kingston, NY , pp. 365–378.
van den Berg, B., Grievink, L., Van der Velden, P. G., Yzermans, C. J., Stellato, R. K., Lebret, E., & Brunekreef, B. (2008). Risk factors for physical symptoms after a disaster: a longitudinal study. Psychological medicine, 38(4), 499-510.
van den Hout, M. A., Engelhard, I. M., Smeets, M. A., Hornsveld, H., Hoogeveen, E., de Heer, E., & Rijkeboer, M. (2010). Counting during recall: Taxing of working memory and reduced vividness and emotionality of negative memories. Applied Cognitive
Psychology, 24(3), 303-311.
van der Kolk, B. A., & Ducey, C. P. (1989). The psychological processing of traumatic experience: Rorschach patterns in PTSD. Journal of Traumatic Stress, 2(3), 259-274. van der Kolk, B. A. (2002). The assessment and treatment of complex PTSD. Treating
trauma survivors with PTSD, 127-156.
van der Kolk, B. A. (2005). Developmental. Psychiatric Annals, 35, 401.
van der Kolk, B. A., Roth, S., Pelcovitz, D., Sunday, S., & Spinazzola, J. (2005). Disorders of extreme stress: The empirical foundation of a complex adaptation to trauma. Journal
of traumatic stress, 18(5), 389-399.
Weiss, D.S. (2004). The Impact of Event Scale-Revised. In J.P. Wilson, & T.M. Keane (Eds.), Assessing psychological trauma and PTSD: A practitioner’s handbook (2nd ed., pp.
168-189). New York: Guilford Press.
Whitaker, S., & Read, S. (2006). The prevalence of psychiatric disorders among people with intellectual disabilities: An analysis of the literature. Journal of Applied Research in
Intellectual Disabilities, 19(4), 330-345.
Wieland, J., Wardenaar, K. J., Fontein, E., & Zitman, F. G. (2012). Utility of the Brief
Symptom Inventory (BSI) in psychiatric outpatients with intellectual disabilities. Journal of Intellectual Disability Research.
Woittiez I. B. & Ras M. (23 juni 2010).Hoe vaak komt een verstandelijke handicap voor? In: Volksgezondheid Toekomst Verkenning, Nationaal Kompas Volksgezondheid.
Bilthoven: RIVM, <http://www.nationaalkompas.nl> Nationaal Kompas Volksgezondheid\Gezondheid en ziekte\Ziekten en aandoeningen\Psychische stoornissen\Verstandelijke handicap.
