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Child Abuse & Neglect

Research article

The relationship between early adversities and attention-deficit/hyperactivity disorder夽 Esme Fuller-Thomson ∗ , Danielle A. Lewis Factor-Inwentash Faculty of Social Work, University of Toronto, 246 Bloor St. W., Toronto, ON, Canada M5S 1A1

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Article history: Received 29 December 2014 Received in revised form 6 March 2015 Accepted 9 March 2015 Available online xxx Keywords: Adverse childhood experiences (ACEs) Attention-deficit hyperactivity disorder Adult survivors of child abuse Child maltreatment Sexual abuse Physical abuse

a b s t r a c t This study examined whether retrospectively reported childhood physical abuse, childhood sexual abuse and/or exposure to parental domestic violence were associated with self-report of a health-professional diagnosis of attention-deficit/hyperactivity disorder (ADHD) among adults. We analyzed nationally representative data from the 2012 Canadian Community Health Survey-Mental Health using gender-specific bivariate and logistic regression analyses (n = 10,496 men; n = 12,877 women). For both men and women, childhood physical abuse was associated with significantly higher odds of reporting ADHD (men odds ratio [OR] = 1.66, p < .001; women OR = 1.95, p < .001). For both genders, childhood sexual abuse was also significantly related to higher odds of ADHD (men OR = 2.57, p < .001; women OR = 2.55, p < .001); however, exposure to parental domestic violence was only associated with elevated odds of ADHD among women (men OR = 0.89, p = .60; women OR = 1.54, p = .03). The results demonstrate a link between childhood physical and sexual abuse and ADHD for both men and women. Future prospective studies are required to further understand this interesting relationship. © 2015 Elsevier Ltd. All rights reserved.

Attention-deficit/hyperactivity disorder (ADHD) affects approximately 4.4% of adults (i.e., 18–44) in the USA (Kessler et al., 2006; Willcutt, 2012; Zwaan et al., 2012). ADHD has three subtypes that describe the symptoms associated with the diagnosis: primarily inattentive, primarily hyperactive/impulsive, and combined inattentive and hyperactive/impulsive (American Psychiatric Association, 2013). The terminology used to describe ADHD has changed several times over the years. In the 1980s, symptoms of inattention with or without hyperactivity were classified as attention deficit disorder (ADD) (American Psychiatric Association, 1980). In 1987, the diagnosis of ADHD was introduced and, in 1994, it was split into the three subtypes used today (American Psychiatric Association, 1994). Since the 1990s, prevalence of the disorder has been rising (Akinbami, Liu, Pastor, & Reuben, 2011). Because ADHD is shown to be highly correlated with a variety of behavioral, social, familial, academic, substance use, and mental health problems (Ryan-Krause, 2010), it is important to consider its early risk factors. Research has begun to demonstrate a relationship between ADHD and adverse childhood experiences (ACEs), including physical abuse, sexual abuse, and witnessing parental domestic violence. Using the National Longitudinal Study of Adolescent Health, Ouyang, Fang, Mercy, Perou, and Grosse (2008) showed that adolescents with a history of childhood physical abuse had higher odds of self-reported symptoms of both inattentive and hyperactive subtypes of ADHD. Those with a

夽 This study was supported by a contract from the Public Health Agency of Canada. The lead author is also supported by Sandra Rotman Endowed Chair, The University of Toronto, Canada. ∗ Corresponding author. http://dx.doi.org/10.1016/j.chiabu.2015.03.005 0145-2134/© 2015 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Fuller-Thomson, E., & Lewis, D.A. The relationship between early adversities and attention-deficit/hyperactivity disorder. Child Abuse & Neglect (2015), http://dx.doi.org/10.1016/j.chiabu.2015.03.005

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history of sexual abuse also had significantly higher odds of the inattentive subtype, but not the hyperactive one. Another large study, this time using a representative sample of adult Canadians, found that those with a history of physical abuse had over six times higher odds of self-reporting a health professional diagnosis of ADHD (Fuller-Thomson, Mehta, & Valeo, 2014). Several smaller clinical studies have also linked ADHD to ACEs: Briscoe-Smith and Hinshaw (2006) found that a higher percentage of girls with ADHD reported any type of abuse than a matched comparison group. They also showed that most of the abuse occurred in the combination ADHD type as opposed to the inattentive type. Ford et al. (2000) revealed, among children and adolescents, that a history of physical or sexual maltreatment was associated with a diagnosis of ADHD. Finally, Biederman et al. (1995) found that children presenting with ADHD at a pediatric clinic disproportionately came from families who had experienced high levels of conflict. The mechanisms underlying the relationship between ACEs and ADHD have yet to be clearly delineated, but may involve at least three pathways: (1) stress resulting from exposure to early adversities may cause changes in brain functioning (Anda et al., 2006) (2) learned experiences of threat and/or deprivation may affect neural development, resulting in alterations in brain structures consistent with ADHD (McLaughlin, Sheridan, Winter, et al., 2014) (3) difficulties inherent to parenting a child with ADHD may increase the probability that physical punishment will be used (Becker & McCloskey, 2002). An assumption following the first pathway is that, because stress is likely to be an outcome of multiple types of ACEs, the types of adversities experienced may be less important than the severity or scope of the experiences over time (McLaughlin, Sheridan, & Lambert, 2014). The second pathway, however, suggests that distinct types of environmental experiences have particular effects on learning and, thus, underlines the importance of distinguishing among varieties of ACEs (McLaughlin, Sheridan, & Lambert, 2014). The third pathway speaks to the increased prevalence of one type of abuse that would most likely result from frustration and inability to cope with a child’s behavioral problems (i.e., physical as opposed to sexual abuse). Because we are uncertain which pathway is most likely, we argue that it is important to consider the independent contribution of multiple types of ACEs. In exploring the relationship between adverse childhood experiences and ADHD there is some justification for analyzing the data separately for women and men. As children, boys are diagnosed with attention deficit/hyperactivity disorder (ADHD) more often than girls (Centers for Disease Control and Prevention, 2008). While research suggests that this trend continues into adulthood (Kessler et al., 2006), a more compelling reason, perhaps, for studying women and men separately, is gender differences in the symptomology, neurobiology, and developmental course of ADHD that have been identified (Nussbaum, 2012). For example, there is research showing that women diagnosed with ADHD in childhood are more likely than their male counterparts to continue to have symptoms in adulthood (Agnew-Blais, Seidman, & Buka, 2013). There is also some evidence that the prevalence of retrospectively reported ACEs varies according to gender, especially a history of sexual abuse, which appears to be more commonly indicated by women (Centers for Disease Control and Prevention, 2010; MacMillan, Tanaka, Duku, Vaillancourt, & Boyle, 2013). Gender-specific pathways linking ACEs to negative health outcomes have also been proposed (Tietjen & Peterlin, 2011), again pointing to the need to consider men and women separately. The goal of our current study is to use a population-based survey of Canadian adults to investigate the gender-specific association between three adverse childhood experiences—physical abuse, sexual abuse, and witnessing domestic violence—and ADHD. Methods The cross-sectional 2012 Canadian Community Health Survey-Mental Health (CCHS-MH) data was used for this study. The survey includes questions related to the health, social, and economic factors that may influence mental health (Statistics Canada, 2013). The CCHS-MH assessed a representative sample of adults aged 15 and older residing in the 10 Canadian provinces. Sample A three-stage design was used to randomly select the CCHS-MH’s sample of respondents. In the first step, geographical locations were selected. Next, households within the geographical locations were selected. Within each household, only one eligible individual was selected to complete the survey (Statistics Canada, 2013). The household-level response rate was 79.8%. Within these 29,088 households, 25,113 individuals provided a completed questionnaire (i.e., person-level response rate = 86.3%). Nationally, this produced an overall combined response rate of 68.9%. For more details on the data set, please see Statistics Canada (2013). The sample for the current study was restricted to respondents over the age of 18 and with complete information on ACEs and/or ADHD as well as the control variables, age and gender. The sub-sample that remained after these exclusions consisted of 10,496 men and 12,877 women. Measures Attention deficit hyperactive disorder (ADHD) Respondents were asked if they had “conditions diagnosed by a health professional that are expected to last or have already lasted 6 months”; attention deficit disorder was one item on the list of health conditions. Because the classification of ADD is no longer used, we assume that those responding positively to this question were either diagnosed with ADD Please cite this article in press as: Fuller-Thomson, E., & Lewis, D.A. The relationship between early adversities and attention-deficit/hyperactivity disorder. Child Abuse & Neglect (2015), http://dx.doi.org/10.1016/j.chiabu.2015.03.005

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between 1980 and 1987 or ADHD from 1987 onward, and still have symptoms of inattention with or without hyperactivity. In other words, we are using a global measure which we refer to, for the sake of ease, as ADHD. Adverse childhood experiences (ACES) Two questions were asked about sexual abuse before the age of 16: (a) “How many times did an adult touch you against your will in any sexual way? By this, I mean anything from unwanted touching or grabbing, to kissing or fondling.” (b) “How many times did an adult force you or attempt to force you into any unwanted sexual activity, by threatening you, holding you down or hurting you in some way?” If respondents responded that either form of abuse had ever occurred, they were defined as having experienced childhood sexual abuse. Respondents were classified as having been exposed to parental domestic violence if they reported that before the age of 16, they had witnessed in their home on at least three occasions “parents, step-parents or guardians hit(ting) each other or another adult”. Individuals were defined as being physically abused before the age of 16 if they reported that an adult had slapped them on the face, head or ears or hit or spanked them with something hard to hurt them at least three times and/or pushed, grabbed, shoved or threw something at them to hurt them at least three times and/or an adult had at least once kicked, bit, punch, choked, burned, or physically attacked them. Control variables All analyses controlled for age by decade, race (self-reported White and non-White), and gender. Statistical analysis Logistic regression analysis was used to investigate the link between the three ACEs (i.e., childhood physical abuse, childhood sexual abuse, and witnessing domestic violence as a child) and ADHD. First, an age–race adjusted odds ratio was generated for each gender to identify the odds of adult ADHD among individuals who had been exposed to parental domestic violence in comparison to those who had not been. Two additional logistic regressions were conducted for each gender to identify the age–race adjusted odds associated with childhood physical abuse and with childhood sexual abuse. To determine the independent association of each of the three ACEs when adjustments were made for the comorbidity of these ACEs, a fourth logistic regression was conducted for each gender in which all three ACEs were included in the same logistic regression as well as age, gender, and race. Due to the complex sampling design of the CCHS, all prevalence data, odds ratios, p-values, and confidence intervals reported were weighted to adjust for the probability of selection and nonresponse. Sample sizes were reported in their unweighted form. Results The prevalence of respondents who reported they had been diagnosed with ADHD (hereafter denoted as those with ADHD) was significantly higher among men than among women (3.1% versus 1.7%, p < .001). As shown in Table 1, both men and women with ADHD had a significantly higher prevalence of childhood physical and sexual abuse and were younger than those without ADHD. Women, but not men, with ADHD reported a significantly higher prevalence of parental domestic violence than those without this disorder. A larger share of men with ADHD identified as White than those without ADHD. As shown in Table 2a, the age–race adjusted odds of reporting a diagnosis of ADHD was nearly two times higher (OR = 1.82) for men with a history of childhood physical abuse, which lowered slightly (OR = 1.66) after adjustment for concurrent ACEs.

Table 1 Gender-specific analyses of adverse childhood experiences, age and race of those with and without attention deficit/hyperactivity disorder (10,496 males and 12,877 female adult respondents). Males without ADD Parental domestic violence No parental domestic violence Childhood physical abuse No childhood physical abuse Childhood sexual abuse No sexual abuse White Aboriginal and/or non-White Age – mean (SD)

6.7% 93.3% 30.5% 69.5% 5.6% 94.4% 77.3% 22.7% 46.7 (17.3)

Males with ADD 8.5% 91.5% 40.9% 59.1% 11.1% 88.9% 84.4% 15.6% 35.6 (14.2)

p-Value .18

hyperactivity disorder.

This study examined whether retrospectively reported childhood physical abuse, childhood sexual abuse and/or exposure to parental domestic violence we...
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