The relation between childhood maltreatment and adult cognitive flexibility performance in delinquents

U

A

MASTER CLINICAL NEUROPSYCHOLOGY

Thesis (14 EC)

THE RELATION BETWEEN CHILDHOOD MALTREATMENT AND ADULT COGNITIVE

Hanneke Verlijsdonk

Student number: 5655714

Email address: Hanneke.verlijsdonk@student.uva.nl

External supervisors: Liza Cornet, Msc and Mylène Böhmer, Msc. First assessor: Anne Geeke Lever, Msc.

Second assessor: Drs. Romke Rouw

Research center /location: Netherlands Institute for the Study of Crime and Law Reinforcement (NSCR)

TABLE OF CONTENT TABLE OF CONTENT ………2 ABSTRACT .………...3 INTRODUCTION .………...4 METHOD .………...7 RESULTS .………..12 DISCUSCCION .………..17 REFERENCES .………..22

ABSTRACT

Background: Previous studies have reported that childhood maltreatment has an important influence on long-term executive functioning performance in the general population. Moreover, studies have shown that childhood maltreatment and poor executive functioning are characteristics of the forensic population. Up until today, only two studies have addressed the relationship between childhood maltreatment and executive functioning in delinquents. Objectives: The study aimed to investigate the relation between childhood maltreatment and adult cognitive flexibility performance, one of the executive functions, in a forensic population.

Methods: Hundred and twenty one delinquents completed the Childhood Trauma Questionnaire (CTQ) and cognitive flexibility performance was administered by the Controlled Oral Word Association Task (COWAT), the Concept Shifting Test (CST) and the Modified Wisconsin Card Sorting Test (M-WCST).

Results: A positive relation was found between CTQ and COWAT. In particular, physical maltreatment predicted a small part of the variance of the COWAT performance. No relation was found between the CTQ and the CST or the M-WCST.

Conclusion: This exploratory study suggests that the neurocognitive profile of abused delinquents is different than that of nonabused delinquents concerning phonemic cognitive flexibility. More research is needed to investigate this neurocognitive profile and the mechanisms behind this profile in order to facilitate the development of special intervention and rehabilitation programs for the abused delinquents in the future.

Key Words: childhood maltreatment, cognitive flexibility, delinquency, executive functioning

Introduction

The degradation of executive functioning processes in delinquents is a topic of debate (Morgan & Lilienfeld, 2000; Ogilvie, Stewart, Chan & Shun, 2011, Raine et al., 2005). Executive functioning is an umbrella term used to describe a compilation of higher order cognitive abilities. It can be defined as “mechanisms by which performance is optimized in situations demanding operation and integration of a set of cognitive processes, including working memory, inhibition, planning, and active monitoring and set shifting” (Robbins, 1998). Impaired performance on executive functioning has been related to antisocial behavior, criminality, delinquency, physical aggression and psychopathy (Morgan & Lilienfeld, 2000; Ogilvie et al., 2011). This suggests that executive functioning processes are a key mechanism in understanding the etiology of criminal and violent behavior.

Executive function deficits in the forensic population might be related to childhood maltreatment as many delinquents experience an unusual level of childhood trauma (Dutton, & Hart, 1992; Driessen et al, 2006; Jespersen, Lalumière, & Seto, 2009; Zager, Busch, Grove, Hughes, & Arbit, 2009). Childhood maltreatment is defined as any act or series by a parent or caregiver that results in harm, potential for harm or threat of harm to a child (Leeb, Paulozzi , Melanson , Simon & Arias, 2008) and is a serious public health problem and societal problem in the European Region (World Health Organization, 2013). The prevalence rates of childhood maltreatment in western countries are high, with rates ranging from 34-59% for neglect, 19-28% for physical abuse, 7-34% for emotional abuse and 9-10% for sexual abuse (Creighton, 2004). Childhood maltreatment is a major risk for developing psychiatric disorders seen in the forensic population including anti-social, anxiety, borderline, mood, narcissistic, obsessive-compulsive and substance use disorders (Afifi et al., 2011; Norman et al., 2012).

Research conducted in the general population in different life stages childhood, adolescence, adulthood, and old age) has shown that childhood maltreatment has an important

influence on long-term executive functioning performance (Gould et al., 2012; Majer, Nater, Lin, Capuron, & Reeves, 2010; Nikulina & Widom, 2013; Spann et al., 2012). All these studies suggested an association between childhood maltreatment and cognitive performance. Furthermore, Narvaez and colleagues (2012) and Sideli and colleagues (2014) have found an association between childhood maltreatment and long-term executive functioning deficits in clinical samples. Although the forensic population shows an unusual level of childhood trauma (Dutton, & Hart, 1992; Driessen et al., 2006; Jespersen et al, 2009; Zagar et al., 2009) the relationship between childhood maltreatment and disturbances in executive function in the forensic population has received little attention.

Currently, only two studies have addressed the effect of childhood trauma on executive functioning within delinquents. In China, Zou and colleagues (2013) have reported that juvenile violent delinquents with childhood trauma showed impaired executive functioning on tasks of attention set shifting, working memory and planning in comparison to non-violent delinquents and controls with childhood trauma. A study conducted in Spain has shown that abused delinquents have poorer performance on psychomotor-cognitive processing speed and cognitive flexibility in comparison with healthy controls (Becerra-García, 2014). Both studies implicate impairments on executive functioning, more specifically mental set shifting, among delinquents.

Mental set shifting involves cognitively switching between numerous tasks, operations or mental sets and is also known as cognitive flexibility (Miyake, Friedman, Emerson, Witzki., & Howerter, 2000). Cognitive flexibility requires an individual to change from a task set that has become insignificant to a new task set that has become relevant (Miyake et al., 2000). The dorsolateral prefrontal cortex is an important area for cognitive flexibility performance (Alvarez & Emory, 2006). Moreover, previous studies have demonstrated that prefrontal dysfunction has been related to childhood maltreatment and criminal behavior (Hart & Rubia, 2012; Yang & Raine, 2009). This suggests that cognitive flexibility performance in

delinquents might be related to the brain damage caused by childhood maltreatment. Therefore, this is an interesting factor to take into consideration for intervention and rehabilitation programs developed for the forensic population.

There are several motives to investigate childhood maltreatment in relation to cognitive flexibility performance in a forensic population. Previous research demonstrated the association of childhood maltreatment with cognitive flexibility performance in delinquents (Becerra-García, 2014; Zou et al. 2013). Although, these studies using qualitative research methods show some insight in the relation between childhood maltreatment and cognitive flexibility performance in this population, a next step is to consider this relationship more in depth by using methodological tools like validated and standardized instruments with psychometric qualities. Furthermore, childhood maltreatment and impaired executive functioning could be important elements to take into account for the intervention and rehabilitation programs of delinquents as these programs focus on impaired executive functioning (Mullin & Simpson, 2007) and impaired executive functioning has been associated with childhood maltreatment in the forensic population (Becerra-García, 2014; Zou et al. 2013).

Given the above stated limitations of previous studies, more research that examines the cognitive performance of delinquents exposed to traumatic events early in life is needed. The objective of this study is to examine the relation of childhood maltreatment and adult cognitive flexibility performance in an Dutch male forensic population. Cognitive flexibility performance will be measured with several neuropsychological tests. Based on previous studies (Becerra-García, 2014; Zou et al. 2013), it is expected that childhood maltreatment will be negatively related to cognitive flexibility performance. Secondly, this study will assess the predictable value of childhood maltreatment on adult cognitive flexibility performance. Third, this study will investigate if the type of abusive event, physical, emotional or sexual, could predict the variation of cognitive flexibility performance within

this group. Based on previous findings (Becerra-García, 2014), it is expected that physical childhood maltreatment will have a negative effect on adult cognitive performance in terms of cognitive flexibility.

Method Participants and procedure

Hundred and twenty one male delinquents, aged between 19 and 58 years, who were convicted and incarcerated in prisons were preselected by a rehabilitation officer for a cognitive behavioral training. After this selection, an admission interview with the delinquent was held by the research team. During this interview, a full explanation of the study procedure was provided and the offender was personally asked to participate. Prior to participation subjects gave written consent to participate in this research by signing an informed consent. Participation was voluntary and subjects could withdraw at any moment. The study protocol was approved by “Medische Ethische Toetscommisie” (METC) of the “Vrije Universiteit” in Amsterdam (VU). Testing took place in an isolated room in prison to avoid distractions. Participants of this investigation were compensated 25 euro for completing the procedure. Materials

Childhood Trauma Questionnaire-Short Form (CTQ-SF). To examine childhood maltreatment the Dutch version of the CTQ-SF was used (Arntz & Wessel, 1996). This version of the questionnaire is derived from the worldwide used retrospective CTQ-SF developed by Bernstein (1994). The CTQ-SF is a self-report questionnaire that consists of 25 items which measures five categories of negative childhood trauma experience: Physical Abuse (PA), Physical Neglect (PN) Emotional Abuse (EA), Emotional Neglect (EN) and Sexual Abuse (SA). PA refers to physical stabbings on a child committed by an older person. PN refers to a lack of basic care such as food, sleep, education, safety, and a combination of these factors for the welfare and development of a person. EA refers to verbal assaults,

treating and humiliating against a child by an older person that could affect the welfare of the child. EN refers to a lack of emotional and psychological support to provide basic needs (e.g. love, care, warmth) and SA refers to sexual assault on a child committed by an older person (Bernstein & Fink, 1998). Item response for each subscale was scored on a 5 point Likert scale (respectively; never true, rarely true, sometimes true, often true, often true). To score the severity of childhood maltreatment the total scale score of the CTQ-SF, which is the total sum of all subscales, was calculated. Furthermore, the subscale scores were taken into account. These scores would permit assessments for effects in all childhood maltreatment categories. In an effort to capture a high proportion of childhood treatment cases, including those of low severity, low/moderate cutoff scores were used to characterize the sample on the topic of childhood maltreatment (Paivio & Cramer, 2004). These cutoff scores are based on data from a nonclinical sample and are appropriate in identifying cases of specific types of abuse and neglect, while using therapist interview ratings as criteria (Bernstein, & Fink, 1998). Several studies (Bogaerts, Daalder, Spreen, Van der Knaap, & Henrichs 2011; Thombs, Bernstein, Lobbestael, & Arntz, 2009) show good internal consistency reliability for the five subscales, ranging from .62 for physical neglect to .95 for sexual abuse, and good criterion-related validity, extending from .50 - .75. Good convergent validity with responses from a semi-structured interview for childhood maltreatment was found. Correlations vary between .46 to .80 (mean r = .62) and are strongly significant (Lobbestael, Arntz, Harkema-Schouten, & Bernstein, 2009).

Controlled Oral Word Association Task (COWAT). The COWAT is a phonemic fluency task that requires the retrieval of words from a long-term storage and executive control of this process: people have to respect rules, shift from searching strategy, inhibit inadequate responses and initiate new behavior (Benton, Hamsher, & Sivan, 1983). In this study the Dutch version developed by Schmand (2000) was used. This version consists of three trails, one minute each, using the letter D, A and T. The examiner asked the subject to

say as many words as they can think of that begin with the given letter. During the task, subjects were prohibited from saying proper nouns, numbers saying a word with the same prefix, words that differ from the previous response by tense or plurality, words that were derived from the previous response. Homonyms of prior responses were acknowledged if the participant could clarify the meaning of the word. Slang and commonly used foreign words were also seen as acceptable responses. In this study, switching scores were calculated and used as a measure of cognitive flexibility performance. Switching was defined as the ability to alter efficiently to a new phonemic characteristic. The change to a new phonemic characteristic occurred in the first letters of the words, when the first and last sounds of the words were the same or when words were homonyms or rhymes. The switching score was calculated as the total sum of the total number of alternations between phonemic characteristics during each trail (Troyer, Moscovitch, & Winocur, 1997). The total number of words generated was also explored in this study. The COWAT has a good intern consistency (r = 0.82) and test retest reliability (r = .78) in healthy subjects between 17 and 89 years of age ( Schmand, Groenink, & Van den Dungen, 2008).

Concept Shifting Test. The CST (Vink & Jolles, 1985) is a modified version of the Trail Making Test (TMT) that measures concept shifting and cognitive speed (Van der Elst, Van Boxtel, Van Breukelen, & Jolles, 2006). The design of the material contains sixteen small circles which are grouped in a larger circle. The small circles contain numbers, letters, both numbers and letters, or are empty. In the first three trails the participants had to cross out as quickly as possible the figures in numerical order (CST Part A), the letters in alphabetical order (CST part B), and the numbers and letters in alternating order (CST Part C). Next, there was a zero condition in which the participants had to cross out the empty circles clockwise as fast as possible (CST zero). The CST zero trail was done twice and serves as a correction for basic motor speed (Van der Elst et al., 2006). To measure cognitive flexibility the shifting score was calculated. The CST A and CST B score were corrected for basic motor speed with

the CST zero trails, CST A score/CST B score = time to complete Part A/Part B – ((time to complete CST zero trail one + time to complete CST zero trail two)/2). The shifting score was calculated by subtracting the average time needed for versions A (numbers) and B (letters) from the total time needed to complete part C (numbers and letters). Several studies suggest that the CST is a useful test to assess set-switching abilities and concept shifting (Rasquin et al. , 2004.; Valentijn et al., 2005; Van der Elst et al., 2006).

Modified Wisconsin Card Sorting Test. The M-WCST (Nelson, 1976) is a modified version of the Wisconsin Card Sorting Test (WCST) developed by Grant and Berg (1948). This test examines the ability to shift cognitive strategies in response to changing environmental contingencies (Schretlen, 2010). The M-WCST consists of four key cards and forty-eight response cards. The subject task was to place the cards one by one under four key cards - one red triangle, two green stars, three yellow crosses, and four blue circles – according to a rule that the subject had to deduce from the examiners feedback to the subjects’ placement of the cards. After six consecutive correct responses, the examiner announced a shift in the sorting rules. After six repeated correct responses to the second rule, the examiner announced another shift and the sorting principle was changed again. Based on these three sorting rules, the participant was required to repeat these rules in the same order a second time. The test was completed when six categories are completed or when all forty-eight cards are used, whichever comes first. The M-WCST was scored according the criteria of Nelson (1976). For this study, the preservative error score of the M-WCST was used as it is useful for documenting problems in forming concepts, profiting from correction, and conceptual flexibility (Lezak, 2004). Good construct validity has been reported, ranging from 0.62 till 0.75 (Lezak, 2004).

Data analysis

Data were analyzed using Statistical Package for the Social Sciences (SPSS) version 19.0 for windows. Individuals (N = 17) with a majority of missing data or missing response

variables were removed from analysis. All statistical analyses were performed with the remaining 104 individuals. Prior to analyses, each measurement method (CTQ, COWAT, CST and M-WCST) was screened for outliers by examining the thumb rule SD = 3 (Barnett & Lewis, 1994; Osborne & Overbay, 2004). Assumptions for normality were tested by the Kolmogorov-Smirnov test. A Spearman’s correlation matrix was used to examine the relation between childhood maltreatment and cognitive flexibility performance. In order to decide which variables from the correlation matrix were entered into regression analyses, a liberal probability level of .10 was used (Mullin & Simpson, 2007). To identify the predictable value of childhood maltreatment on adult cognitive flexibility performance a linear regression model was conducted. In this regression model childhood maltreatment was seen as the predictor and cognitive flexibility performance measured by the COWAT as the outcome variable. Assumptions for homoscedasticity, independent errors, normality of distribution and linearity were tested. In addition, to examine which type of maltreatment, physical, emotional or sexual, had a good predictable value on the variation of the COWAT performance a multiple linear regression model was carried out. In this model the types of childhood maltreatment (physical, emotional and sexual) were seen as predictor variables and COWAT performance as the outcome variable. Assumptions for homoscedasticity, independent errors, normality of distribution and linearity were tested. As it is hypothesized that physical childhood maltreatment has a negative effect on cognitive flexibility performance (Becerra-García, 2014; Zou et al. 2013) the enter method of multiple regression was used. All statistical analyses (e.g. Spearman’s correlation matrix, linear regression models, multiple regression models) used the bootstrap estimation with 95% bias corrected and accelerated confidence intervals (BCa CI) based on 2000 bootstrap (Wright, London & Field, 2011).

Results

Sample characteristics in terms of age, scores on neuropsychological tests quantifying cognitive flexibility and childhood maltreatment are presented in Table 1.

Before analyzing the data of the CTQ questionnaire, straight line responders (N=1) were removed from the sample assuming that these responders did not fill out the questionnaire seriously. The mean CTQ score of childhood maltreatment is 34.48 (SD = 10.56; range 25 to 75). To determine the history of childhood maltreatment, low to moderate cut-off scores applied to CTQ subscale score are used. Low or moderate childhood maltreatment in at least one of these subscales is reported by 60% of the sample. Furthermore, 27% of this sample was classified positive for a history of EA , 29% for a history of EN, 27 % for a history of PA, 31% for a history of PN, and 12% for a history of SA. Table 1 shows the internal consistency reliability of the five subscales and total score of the CTQ, ranging from 0.58 to 0.90, within this sample.

Table 1

Sample characteristics in terms of age, scores quantifying childhood maltreatment and cognitive flexibility.

Note. CTQ = Childhood Trauma Questionnaire; COWAT = Controlled Oral Word Association Test; CST =

Concept Shifting Task; M-WCST= Modified Wisconsin Card Sorting Task. a_{The variation in sample size is due to the deleted cases according the SD=3 thumb rule.}

To explore the possible relationship between childhood maltreatment and cognitive flexibility a Spearman’s correlation matrix1 _{was calculated. In this matrix no significant} correlations were found between the CTQ scores and the CST shifting score or M-WCST perseverative error score. However, several significant correlations between the CTQ scores

1_{It is interesting to note that a strong correlation between the COWAT switch score and COWAT total} number of words, r = .938, 95% BCa CI [.896, .966], p = .000, was found in this correlation matrix.

Characteristic N Mean Standard

deviation

Minimum Maximum Cronbach’s alpha Age 104 28.75 7.50 19.00 58.00 CTQ – Total score 92 34.48 10.56 25.00 75.00 .85 Emotional abuse 101 7.46 3.47 5.00 18.00 .83 Emotional neglect 100 8.58 4.34 5.00 21.00 .90 Physical abuse 99 7.11 3.15 5.00 18.00 .87 Physical neglect 98 6.91 2.33 5.00 16.00 .58 Sexual abuse 98 5.42 1.34 5.00 11.00 .88

COWAT switch score 103 22.27 7.67 5.00 41.00

CST Shifting score 102 10.60 10.62 -1.41 66.88

and COWAT switch score were found. The total score of the CTQ was significantly positively correlated with the switch scores of the COWAT, r = .266, 95% BCa CI [.005, .451], p = .005. Besides the score of the subscale EA, r = .251, 95% BCa CI [.005, 0.435], p = .008, PA, r = .326, 95 % BCa CI [.141, .489], p = .001 and PN, r = .198, 95% BCa CI [-.033, .402], p = .003 are significantly positively correlated with the switch score of the COWAT.

In order to decide which variables from the correlation matrix should be entered into regression analyses, a liberal probability level of .10 was used to enter a variable into the equation. Six predictor variables; total score CTQ and the subscales scores EA, EN, PA, PN and SA met these criteria for the outcome variable COWAT switch score (Table 2).

Table 2

Correlations between predictor and outcome variables.

Cognitive flexibility performance

COWAT switch score CST shifting score M-WCST preservative error CTQ – Total score .266* _{.023 .002} Emotional abuse .251* _{.096 -.006} Emotional neglect .126* _{-.032 -.114} Physical abuse .326* _{.104 .072} Physical neglect .198* _{.086 -.061} Sexual abuse .138* _{.086 .045}

Note. COWAT = Controlled Oral Word Association Test; CST = Concept Shifting Task; M-WCST= Modified

Wisconsin Card Sorting Task; CTQ = Childhood Trauma Questionnaire. a * _{= p < .100, one tailed.} b _{N = 92 for COWAT, N = 91 for CST and N = 88 for M-WCST}

To examine whether childhood maltreatment predicts adult cognitive flexibility performance a linear regression model between the total score of the CTQ and the switch score of the COWAT was conducted out. The assumptions of homoscedasticity and linearity were not met and therefore a bootstrap regression was used. The model was significant, F (1, 91) = 5.304, p = .024, and explains 5.6% of the variation in childhood maltreatment quantified by the total score of the CTQ. The relation between COWAT switch scores and childhood maltreatment is positive (β = 0.234). This indicates that participants with a higher maltreatment score make more switches on the COWAT task.

In order to measure if a type of childhood maltreatment, physical, emotional or sexual predicts adult cognitive flexibility performance quantified by the COWAT switch score a multiple regression model was carried out. The assumptions of homoscedasticity and linearity were not met and therefore a bootstrap multiple regression was used for analyses. In terms of multicollinearity, none of the predictor variables are found to correlate too highly with each other (i.e. r = .7). Table 3 shows the regression equations. Significant statistically models F ( p ≤ .05) were found for step 1, physical maltreatment, and step 2, emotional maltreatment. The predictor model for physical maltreatment is significant, F (2, 91) = 4.393, p = .015. This model explains 9.00% of the variance of the COWAT switch score. The relation between PA, PN (physical maltreatment) and the COWAT switch score was positive, β = 0.217 for PA and β = 0.152 for PN. The predictor model for emotional maltreatment is also significant, F (2,91) = 2.767, p = .032. This model explains 11,3 % of the variance of the COWAT switch score. The relation between EA and COWAT switch score is positive, β = 0.119 and the relation between EN and COWAT switch score is negative, β = -.237.

Table 3

Multiple Linear Regression model for COWAT performance predicted by the type of abusive event, physical, emotional or sexual maltreatment.

COWAT switch score

Predictor R² B Std error B β p Step 1 .090 .015 Physical abuse .579 .282 .217 Physical neglect .534 .372 .152 Step 2 .113 .032 Physical abuse .540 .403 .202 Physical neglect .947 .466 .270 Emotional abuse .305 .438 .119 Emotional neglect -.462 .308 -.237 Step 3 .115 .059 Physical abuse .635 .465 .238 Physical neglect .975 .472 .277 Emotional abuse .312 .441 .122 Emotional neglect -483 .313 -.248 Sexual abuse -.321 .768 -.056

Discussion

The aim of this study was to investigate the relation between childhood maltreatment and adult cognitive flexibility performance in a Dutch male forensic population. Therefore, scores on the CTQ quantifying childhood maltreatment were examined in relation to different forms of cognitive flexibility. First of all, the current study observed that about 1/3 of the sample reported a category of childhood maltreatment. These numbers are consistent with previous research (Dutton & Hart, 1992; Driessen et al., 2006; Jespersen et al., 2009; Zagar et al. 2009).

In addition, the present study found an association between childhood maltreatment and the ability to shift efficiently between phonemic characteristics, the cognitive flexibility performance measured by the COWAT. Based on previous studies (Becerra – García, 2014; Zou et al., 2013) it was hypothesized that childhood maltreatment would be negatively related to cognitive flexibility performance. Contrary to this hypothesis, a positive relationship between childhood maltreatment and the ability to shift efficiently between phonemic characteristics was found. This suggest that childhood maltreatment is associated with a better performance on this task. Unfortunately, until today the mechanisms behind this relationship remain unclear. Although there is no evidence in literature regarding this relationship, it might be hypothesized that abused delinquents develop good phonemic cognitive flexibility skills as this could be a method to prevent childhood maltreatment, especially physical maltreatment. By coming up with several different verbal arguments a child might be able to stop the older person from physical stabbings or assaults.

Furthermore, the current study indicates that childhood maltreatment, especially physical maltreatment, predicts a small part of the variance for this form of cognitive flexibility. The findings suggest that childhood maltreatment, especially physical maltreatment, could be an important factor to take into consideration while examine phonemic cognitive flexibility.

Nevertheless, this study did not reveal a relationship between childhood maltreatment and cognitive flexibility performance quantified by the CST, the cognitive speed of shifting between two concepts, and M-WCST, the capacity to shift cognitive strategies in response to alternating environmental contingencies. This is inconsistent with previous research (Becerra-García, 2014; Zou et al, 2013). Becerra-García (2014) found that delinquents with a history of childhood maltreatment showed a poorer performance of psychomotor-cognitive processing and cognitive flexibility. Zou et al. (2013) reported that juvenile violent delinquents with childhood trauma showed impaired executive functioning on tasks of attention set shifting.

The inconsistencies between current and past findings could be partly explained by several factors. First of all, the current study uses different instruments assessing childhood maltreatment and cognitive flexibility compared to past research. Besides, past studies had different sample sizes. Furthermore, Zou et al (2013) used a different type of delinquent, age-stage, for their research. Furthermore, cultural differences could have influenced the results(ref). Perhaps even school system, as it is different in every country, could have had an influence on adult cognitive flexibility performance, which may have lead to different results.

To summarize, the present study suggests that some types of cognitive flexibility performance are not associated with childhood maltreatment and others, contrariwise, are. Previous research shows that war veterans or rape survivors, who suffer from a Post Traumatic Stress Disorder (PTSD) due to an experienced trauma earlier on in life, have no deficit in attention-shifting performance tasks (Barrett, Green, Morris, Giles & Croft, 1996; Jenkins, Langlais, Delis & Cohen, 2000; Vasterling, Brailey, Constans, & Sutker, 1998; Vasterling, Rogers, Kaplan, 2000). This suggest that performance on attention-shifting tasks like the CST or the M-WCST is not affected by an experienced trauma earlier on in life. In addition, Flaks et al. (2014) show that executive functions like mental set shifting are differentially affect by post-traumatic stress disorder and trauma in a population who suffered

from urban violence. This study suggest that trauma or violence has a different effect on cognitive functions like mental set shifting.

It might be deduced from this study that abused delinquents have a different neurocognitive profile then non abused delinquents. This could have important implications for intervention and rehabilitation programs developed for the forensic population in the future. For instance, delinquents with childhood maltreatment could need a different rehabilitation program than a non abused delinquent. More research is needed to investigate the neurocognitive profiles of the delinquent as little is known about this topic at the moment. The results of the present study should be considered in light of the following limitations. First of all, important factors like age and IQ were not taken into account in the present study. Previous research has shown that cognitive and executive functioning declines with age (Salthouse & Davis, 2006; Salthouse & Schroeder) and that a IQ is associated with executive functioning and frontal lobe function (Duncan, Burgess & Emslie, 1995). Several studies suggest that verbal intelligence has a significant effect on COWAT performance (Bolla et al. 1998; Miller, 1984; Schmand, 2008). Hence, the positive relationship between childhood maltreatment and COWAT performance found in the present study might be declared by estimated verbal IQ.

Secondly, more information is needed to draw a conclusion on the neurocognitive profile of abused offenders. Brain development and functioning is damaged by childhood maltreatment (Hart & Rubia, 2012). On the other hand, it might be speculated that an abused delinquent could have developed compensating behavior in order to prevent childhood maltreatment for happening. Both could have led to different brain development and the mechanisms of this development remains partly unknown until today. It might be possible that the result of the current study could be explained by these unknown mechanisms.

Third, the current study relied on a self-report instrument to quantify childhood maltreatment. Problems concerning the reliability of self-report instruments include

non-awareness, nondisclosure, reporting biases due to mood states or something else and simple forgetting. This means that false and negative positives could occur in the data collected by the self-report questionnaire. However, the use of validated psychometric instruments increases the validity of self-reported data (Hardt & Jutter, 2004). Yet, a suggestion for future research would be to carry out a validated and standardized psychiatric interview with good psychometric qualities for childhood maltreatment in addition.

Despite these limitations the present study also contains certain strengths. First of all, this is the first study to investigate the neuropsychological construct cognitive flexibility/mental set shifting, one of the executive functions, in relation to childhood maltreatment in the forensic population. Secondly, to date cognitive flexibility is administered by several neuropsychological tests like the COWAT, CST and M-WCST which all measure the concept cognitive flexibility. Previous literature suggest that this behavioral construct does not exist of more aspects and that all tests measure the same, namely cognitive flexibility (Boone et al., 1998; Busch et al., 2005). This study proposes that cognitive flexibility is a broader concept with more aspects which can be addressed by the neuropsychological tests already known. More aspects of cognitive flexibility should be included in future investigations in order to draw a good conclusion on cognitive flexibility dysfunction.

Finally, a strong relation between the total number of words generated and the switch score of the Troyer scoring system (1997) for the COWAT task is found in the present study. This suggests that the scoring system of Troyer is a good measurement method for phonemic cognitive flexibility performance. Although the switching score defines the construct of phonemic cognitive flexibility performance more accurately, currently the total number of words generated is used to measure this construct in the discipline neuropsychology. As a strong relation is found between the two scores in the forensic population, a specific clinical population, it should be worth to consider the use of the scoring system of Troyer for other goals ends then research only.

With these caveats and strengths in mind, certain recommendations can be made for future research studies and intervention or rehabilitation programs designed for the forensic population. Since the relationship between childhood maltreatment and phonemic cognitive flexibility was not previously investigated, more research is needed to confirm or refute these findings. It is recommended that further research be conducted on this topic includes other important factors like age, IQ or current or lifetime psychiatric disorders as these factors were not included in the above investigation. Moreover, there might be other underlying mechanisms which could declare the positive relationship between childhood maltreatment and adult cognitive flexibility in the forensic population suggested by the present study.

In addition, it is recommended that future research examines other executive functions like inhibition, planning and working memory in relation to childhood maltreatment since both concepts are characteristics of the forensic population. More research is needed to investigate whether other executive functions are affected by childhood maltreatment. This research should not only address the relationship between these concepts but also the mechanisms which are responsible for childhood maltreatment and distorted executive functioning in the forensic population.

The findings of this study might be important for the real life world, not just only for science. The present study suggests that different neurocognitive profiles exist within the forensic population. Maybe these different neurocognitive profiles should be considered while developing intervention and rehabilitation programs for the forensic population. Furthermore, neuropsychological tests should be considered as a comprenhensive intervention or rehabilitation strategy as these instruments could be a useful tool to gain insight in the neurocognitive abilities and profile of the delinquent. It could be that findings from this type of research could help intervention and rehabilitation programs for the forensic population become more effective in the future.

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