A Systematic Review of Polyvictimization among Children with Attention Deficit Hyperactivity or Autism Spectrum Disorder

Compared to typically developing (TD) children, children with ASD and ADHD are more likely to be victims of peer victimization, child maltreatment, and other forms of victimization. Polyvictimization is used as a concept to examine vulnerability to multiple forms of victimization experienced in different contexts. However, little is known about polyvictimization among children with specific forms of disability, such as ASD or ADHD [7]. Polyvictimization is defined as exposure to multiple forms of abuse, victimization, or violence including, but not limited to, conventional crime, child maltreatment, peer and sibling victimization, sexual assault, and witnessing and indirect victimization [8]. Polyvictimization can also be expressed as exposure to violence in different settings or environments, such as the school, home, and community. Examining polyvictimization could help account for large variations in the traumatic symptoms seen in children subjected to various forms of childhood adversity [9]. Due to their stressful life situation, it is of particular importance to understand the vulnerability of children with ASD or ADHD and the intersections of violence and victimization across these different contexts and domains of exposure [10].

Peer victimization is defined as repetitive and intentional aggressive behavior that is systematic and involves inequality in power between the perpetrator(s) and the victim [11]. Peer victimization can take place ‘face-to-face’ or via electronic media [12]. Approximately 44% of school-aged children with ASD report peer victimization, where verbal bullying is the most common form of bullying reported [13]. In the USA, prevalence rates as high as 94% have been reported by mothers of children with ASD [14]. Children and adolescents with Asperger’s syndrome and/or with milder deficits in social understanding, early adolescents, those attending mainstream school, and those with concurrent behavioral difficulties are those most at risk of peer victimization. The inclusion of children with ASD in mainstream schools are becoming increasingly more common and there is concern that this affects their involvement in peer victimization and their school performance negatively due to the symptoms associated with the disabilities [5,15]. While a mainstream school setting offers important opportunities for growth in social competency for adolescents with ASD, it may also increase the probability of negative peer interactions and experiences [16]. However, the results regarding the impact of school setting and the risk for peer victimization among students with ASD are conflicting [17,18].

Adolescents with ADHD is a group with an increased risk of peer victimization compared to TD youth. Research on ADHD has mostly been based on male samples, with focus on girls emerging relatively recently. Compared to TD youth, girls with ADHD demonstrate higher levels of peer rejection, which in turn predict poorer social adjustment and a host of problem behaviors [19]. For young adolescents with ADHD, Becker et al., [6] found that 51% of students ages 11–15 reported relational victimization but found no sex differences regarding relational or reputational victimization. However, males with ADHD reported more physical victimization than females. The risk of exposure to peer victimization as well as abuse and maltreatment in the home are elevated among children with chronic health conditions. This means that frequent peer victimization warrants particular vigilance as it appears to be an indicator of severe violence at home [20].

Child maltreatment, which is also referred to as child abuse or neglect, is defined as “all forms of physical and/or emotional ill-treatment, sexual abuse, neglect, negligence, and commercial or other exploitation, which results in actual or potential harm to child’s health, survival, development or dignity in the context of a relationship of responsibility trust or power. Exposure to intimate partner violence is also sometimes included as a form of child maltreatment” [21]. Children with disabilities are more likely to be victims of child abuse than their TD peers, where higher levels of disability are associated with an increased risk of abuse [22]. Chronically maltreated children also appear to be at high-risk for developing clinical levels of problems [23]. Further, children with ASD have shown to be between two to three times more likely to experience maltreatment compared to population controls, with a substantial elevated risk for physical abuse [24]. A follow-up study of maltreatment in girls with ADHD found that twice as many girls with ADHD (22.9%) reported at least one form of maltreatment at a five-year follow-up compared to girls without ADHD (11.4%) [25].

Further, ADHD symptoms of the inattentive types have shown associations with supervision neglect, physical neglect, and physical and contact sexual abuse, while the hyperactive types of symptoms have shown an increased risk for supervision neglect and physical abuse [26]. Parents of children with ADHD may experience increased levels of parenting stress compared to parents of TD children, with predictors including child externalizing and internalizing problems, maternal depressive symptoms, parental ADHD diagnosis, and low marital quality [27]. It has been suggested that children with disabilities may be at greater risk for maltreatment because their extensive needs and/or behavioral difficulties can trigger maladaptive responses in some parents [28].

Other forms of victimization commonly reported among children and adolescents include violence in the community and in the neighborhood, both own exposure to violence and witnessing different forms of violence. Exposure to violence in combination with witnessing violence have shown to increase the risk of internalizing and externalizing problems, as well as child and adult health risk indicators [29]. There is robust evidence that exposure to interparental aggression is associated with significant disruptions in children’s psychosocial functioning, especially among preschoolers [30]. Being both victim-of and witness-to violence is significantly associated with ADHD symptoms, particularly among girls [31]. Further, a study by Brown et al. [32] found that children with ADHD reported a significantly higher prevalence of nine different types of adverse childhood experiences (ACE) compared to children without ADHD, including neighborhood violence (20.1% vs. 9.5%; p < 0.001) and domestic violence (15.2% vs. 6.4%; p < 0.001). Similar results were found by Fuller-Thomson and Lewis [33] who used a retrospective design to explore the relationship between early adversities and ADHD. Their results showed that for both men and women, childhood sexual abuse was significantly related to higher odds of ADHD (men OR = 2.57, p < 0.001; women OR = 2.55, p < 0.001), while domestic violence was only associated with elevated odds of ADHD among women (OR = 1.54, p < 0.03).

In 2005, Finkelhor, Ormrod, Turner, and Hamby [8] introduced the construct of “polyvictimization” arguing that more comprehensive investigations of violence against children were required, so that the experiences of those affected by multiple forms of violence were understood accurately [34]. There are reasons to believe that children who are exposed to one form of victimization also experience other forms of victimization [35,36,37]. Focusing on only one or a few forms of child victimization is likely to substantially underestimate the full burden of victimization exposure and the full strength of the relationship between victimization and child mental health [38]. Further, even low-frequency polyvictimization appears to have a more severe impact than high frequency single-victimization [9], which supports polyvictimization as a unique and important construct for schools and other authorities to understand the whole situation of the victims. Despite research showing an increased risk for victimization among children and adolescents with ASD and/or ADHD, very few studies have studied the vulnerability of children with ASD and/or ADHD of exposure to multiple forms of victimization. Ford, Wasser, and Connor [39] studied polyvictimization among psychiatrically impaired children and found that 22.8% among 259 outpatient admissions had experienced at least two forms of victimization. Of these, 83% reported sexual abuse, 78% reported physical abuse, and 86% reported other trauma history.

As polyvictimization has been associated with mental ill-health and psychiatric symptoms [10,40,41,42], it is important to study this phenomenon further, especially among the vulnerable group of children and students with ASD and ADHD. Due to their stressful life situation, children with ASD or ADHD may be more susceptible to multiple forms of victimization. Hence, the focus in this systematic review is to highlight the vulnerability of victimization in different contexts, i.e., in school, at home, and in the community. This review does not seek to separate cyber victimization as a different arena for victimization as it could be a tool for victimization in school, at home, as well as in the community.

Research results on prevalence rates of victimization among children and youth with ASD and/or ADHD are ambiguous. One explanation of the great variation in prevalence rates could be the various forms of gathering this data where different instruments and informants are used. The main research tool used to measure polyvictimization to date has been the Juvenile Victimization Questionnaire (JVQ). The JVQ includes 34 forms of offenses against youth that cover five general areas of concern (1) Conventional crime (eight questions, e.g., robbery), (2) Child Maltreatment (four questions including physical, emotional and neglect), (3) Peer and Sibling Victimization (six questions, e.g., bullying), (4) Sexual victimization (seven questions including peer or adult perpetration), and (5) Witnessing and Indirect Victimization (nine questions, e.g., witnessing family violence, witnessing an assault with a weapon) [43]. When presenting the results from studies using JVQ, the results will be presented according to these five areas. While self-reports are the most commonly used method for gathering data on peer victimization among TD, parental reports [14,44] or teacher reports [45] are the most common among children with ASD. It has been suggested that this may be based on the belief that children and youth with ASD are unable to answer questions on peer victimization due to their inability to understand complex social situations [46]. Experiences with peer victimization as reported by ASD youth themselves may differ from those typically measured in questionnaires, indicating that their personal experiences and perceptions of such victimization are not well understood [47]. Research involving both parental, and self-reports have found no differences in reported prevalence rates regarding cyberbullying [48], while other research has used different questions for parents and their children [49]. A comparison of teacher and parent reports shows that parents tend to rate their child as a victim of bullying to a higher degree than teachers, which is likely to reflect the different environments in which teachers and parents see children [50]. Adams, Fredstrom, Duncan, Holleb, and Bishop [51] tested the association between peer victimization and internalizing symptoms in adolescent males with ASD using self-reports. Their results showed that the self-report measure was valid and reliable and associated with internalizing symptoms even after controlling for parent reports of peer victimization. This highlights the importance of also using children themselves as informants instead of solely relying on parental reports.

This review was registered (registration number: CRD42019128779) with the PROSPERO international prospective register of systematic reviews, the Centre for Reviews and Dissemination, University of York, and the review protocol published on this database on 15 April 2019.

In this review, polyvictimization is defined as exposure to multiple forms of abuse, victimization, or violence, including, but not limited to, conventional crime, child maltreatment, peer and sibling victimization, sexual assault, and witnessing and indirect victimization [8]. This review does not treat cyber victimization as a separate form of victimization, merely as a tool for different forms of victimization [52]. The word polyvictimization (by definition, exposure to multiple forms of victimization) was chosen in this review and the included studies must investigate at least four different forms of victimization. Information about (i) the number of different forms of victimization, (ii) the frequency of victimization, (iii) background information for example type of disability/disabilities, age, sex, as well as (iv) study design and assessment methods used, are sought for the included articles.

Relevant studies were identified using two search strategies. First, an online search was performed in five databases: PsycInfo, ERIC, ERC, Scopus, and PubMed, until 12 March 2019. Search terms consisted of three main concepts related to the research questions: polyvictimization, children or adolescents, and ASD/ADHD diagnosis (see Appendix Table A1). Second, a hand search in reference lists of included papers, conference reports was performed to identify relevant articles that may have been missed in the online search. Searches were also performed in Google and Google Scholar search engines.

All identified articles were initially assessed against the inclusion and exclusion criteria. The eligibility of the studies was based on the title and abstract. If the assessments concluded that a study was potentially eligible, the full article was retrieved for further assessment. In the second screening phase, full text papers were assessed independently by the reviewer using a standardized data extraction form designed to describe the characteristics of studies to be included as set out in the recommendations in the Cochrane Handbook Section 5.1.0 https://handbook-5-1.cochrane.org/↗.

Extracted data items included the following characteristics for each study: information about the study sample (age-range, sex, medical diagnosis), country were study was conducted, study design, sample size, survey method, survey informant, types of victimization assessed, prevalence of victimization, frequency (how often victimization occurred), and intensity (severity of the act), if reported.

The quality of each study and risk of bias was assessed using the Standard Quality Assessment Criteria For Evaluating Primary Research Papers “QualSyst” [55]. As only quantitative studies are included in this review, the Checklist for Assessing the Quality of Quantitative Studies in QualSyst was used. There are 14 questions in this checklist; for each of which a score of 0 (No), 1 (Partial), or 2 (Yes) can be given. An option of Not Applicable can also be chosen if the question does not apply to the study (for example, a question about randomization is not applicable for a cross-sectional study). A total score is calculated as the sum of all the scores for each question. A summary score is then calculated as the division between the total score and the total possible sum (which is calculated as 28—(number of “not applicable” * 2)). The summary score may range from 0 to 1. In addition to these, an additional item about whether ethics approval had been granted for the conduct of the study is included [34].

A total of 1300 articles were identified in the data base searches. Five additional records were identified through reference lists. Thirty articles were read in full to determine their inclusion eligibility. Reasons for exclusion included wrong age group (n = 3), the target group had no specified ASD or ADHD diagnosis (n = 5), no prevalence rates were reported in the results (n = 1), only one type of victimization was assessed (n = 12), victimization was not reported as the outcome (n = 1) and the article used selective subgroups including adolescents with suicidal behavior (n = 1) and depression (n = 1). Of the 12 articles excluded based on number of victimization types assessed, four examined only peer victimization, six assessed maltreatment and two assessed abuse. A total of six articles met the criteria for inclusion in this review (see Figure 1, flow chart). Together they reported data from 9020 adolescents and adults ranging in sample sizes from 92 to 4114. All studies but one [56] used samples with predominantly men.

The characteristics of the included studies are summarized in Table 1.

In line with previous studies [34], items 5–7 of the QualSyst were not applicable and thus removed from the quality assessment as the included studies were epidemiological and not clinical trials. The total QualSyst score was 22 (see Table 1). Overall, the total sum scores ranged from 17 to 22. Mean score was 20 and summary scores ranged from 0.77 to 1.0 (out of 1.0). Three studies received maximum score (22). All except one study [58], included information about ethics approval. For detailed assessment scores, see Appendix Table A2.

The overall prevalence of polyvictimization among children with ASD or ADHD could not be estimated in this review due to the small number of studies presenting these types of data. Only two studies reported prevalence rates for polyvictimization. Among children exposed to four types of victimization or more, the reported prevalence rates were 1.8% and 23.1% for children with ASD and 7.3% for children with ADHD [59,60]. There were general tendencies showing that children with ASD or ADHD are exposed to more victimization reported as odds ratios, relative risks, or risk ratios, compared to typically developing children. One study found a strong relationship between bullying and child maltreatment as half of the children reporting bullying also reported child maltreatment [57]. This is confirmed in other research showing a strong association between bullying experiences (both as victim and perpetrator) and child abuse, indicating that bullying appears to be an indicator of severe violence in the home [20]. Considering this strong relationship, it is interesting that only one of the studies included in this review included questions on cyber bullying when measuring sibling/peer victimization [59]. This means that cyberbullying, which is an important arena for victimization, may be unreported when it comes to victimization and polyvictimization among children with ASD and ADHD. A recent review showed that children with neurodevelopmental disorders (including ASD and ADHD) may be involved in cyber bullying to a greater extent compared to typically developing children [18]. However, lack of recognition about new forms of victimization, such as cyberbullying, and their harmful impacts on health and well-being means that parents, teachers, and other people may not be aware of such forms of victimization [34].

Among the reported forms of victimization, peer/sibling victimization received the highest prevalence rates, ranging from 21.5–83.3% among children with ASD and 33.5–67.9% among children with ADHD. This is similar to previous research on peer victimization among students with ASD [13] and ADHD [6]. Prevalence rates of peer-victimization among children with ASD and ADHD were only directly compared in one study [59] who found a slightly higher prevalence rate among students (6–18 years) with ADHD in the preceding year. The same study showed an increase risk of most forms of victimization among children in inclusive school settings compared to children in segregated school settings. It is debated whether the inclusion of children with ASD in mainstream schools leads to higher rates of peer-victimization while a segregated school setting could work protectively [5,15,59]. To be able to draw more reliable conclusions, more research on this topic is needed. As suggested previously, frequent peer victimization appears to be an indicator of severe violence at home [20]. Regarding child maltreatment in the current review, in conformity with peer-victimization, children with ASD reported prevalence rates ranging from 16.2–50.4% compared to 16.9–30.0% among children with ADHD. The included studies also showed that children with ASD reported significantly higher prevalence rates for peer and sibling victimization [60] and child maltreatment [59,60] compared to typically developing children. In this review, the lowest prevalence rates for child maltreatment were reported in the studies using parents as respondents [7,60]. Child maltreatment could be a somewhat complicated form of victimization to investigate among children with ASD and ADHD. As parents or caregivers to children with these diagnoses often are the respondents, it could imply a great number of unrecorded cases due to shame or fear of negative consequences of reporting [63]. Further, the prevalence rates for conventional crime, sexual abuse, and witnessing and indirect violence were 34.6–75.5%; 6.6–38.2%; and 14.0–41.5%, respectively, among children with ADHD, and 8.1–64.2%; 2.8–27.3%; and 5.9–30.0%, respectively, for children with ASD. It appears that children with ASD and ADHD are particularly vulnerable to victimization involving the most important and meaningful relationships (peers, siblings, parents or legal guardians). This could be explained by the nature of the ASD and ADHD diagnosis. It has been suggested that children with disabilities may be at greater risk for maltreatment because their extensive needs and/or behavioral difficulties can trigger maladaptive responses in some parents [28]. Children with ASD also tend to have communication deficits, such as responding inappropriately in conversations, misreading nonverbal interactions, or having difficulty building friendships appropriate to their age [3] as well as behavior problems and difficulty with social skills [4]. They may also experience challenges in understanding their own and others’ behavior [64] and have difficulties with self-regulation of their behavior and emotions [65,66]. Further, children with ADHD also exhibit externalizing symptoms, including impulsivity, attention problems, and aggression, which are traits that peers and parents may find aversive and that will lead to difficulties with socialization and caregiving demands [7]. Much of the earlier peer victimization research has identified these characteristics as risk factors for peer victimization involvement and found that children with ASD and ADHD are especially prone to social victimization [48,67]. As Rose and Espelage [68] have argued, it is not the disability itself that is a risk factor but the characteristics associated with the disability.

Of the six included studies in this review, only one relied solely on self-reports [56] to measure victimization. Two of the studies reported that ethical restrictions around the direct questioning of children with disabilities prohibited them to perform the assessments with children and youth [57,60]. Some of the studies discussed the use of parental respondents as a study limitation due to recall bias. For example, under-reporting of certain types of victimization, especially victimization in the home and under-reporting due to caregivers’ unawareness of the child’s exposure to certain types of victimization because of ignorance or the unwillingness to share this information. Using self-reports were also discussed as a limitation when selection of youth included only children with high functioning autism and Asperger’s syndrome who were able to fill in the self-report measure used in the study. Due to the nature of the disability, many researchers discuss the reliability of self-reports among children with ASD [15,69]. It is discussed that the symptoms and characteristics of the disability, i.e., difficulties understanding the thoughts, emotions, reactions, and behaviors of others, that makes them the ideal target for bullying may also make it hard for them to perceive and report bullying and victimization in a reliable and valid manner [70]. While many argue that children with ASD are unreliable respondents of victimization, under-reporting using parental and teacher reports have been shown in research on peer victimization [71,72] and child maltreatment [63]. Experiences with peer victimization as reported by ASD youth themselves may differ from those typically measured in questionnaires, indicating that their personal experiences and perceptions of such victimization are not well understood [47]. It may be difficult for children with ASD to differentiate between playful teasing amongst friends and hurtful teasing. Therefore, qualitative methods may be particularly useful in determining how respondents define and understand their own bullying perpetration and victimization experiences [15]. As research has shown that self-report measures associate with internalizing symptoms in children with ASD, using children themselves as informants instead of solely relying on parental reports is important to grasp the full impact of victimization [51].