The occurrence and co-occurrence of ACEs and their relationship to mental health in the United States and Ireland

Abstract

Background
Adverse childhood experiences (ACEs) have various deleterious effects on mental health but few studies have been conducted in Ireland.

Objective
The primary objective was to determine if there were significant differences in occurrences of ACEs in U.S. and Irish adults. We also sought to determine if there were unique associations between individual and multiple ACE events and mental health.

Participants and setting
Preexisting nationally representative adult samples from the U.S. (n = 1893) and Ireland (n = 1020) were utilized for analysis.

Method
To determine if there were significant differences in the occurrence of specific ACE events and the mean number of ACEs experienced by U.S. and Irish adults, chi-square difference tests and an independent samples t-test were used, respectively. Binary logistic regression was used to examine the unique associations between ACE events and major depressive disorder (MDD), generalized anxiety disorder (GAD), posttraumatic stress disorder (PTSD), and Complex PTSD (CPTSD). Nationality, sex, age, and educational level were included as covariates and adjusted odds ratios are reported.

Results
Irish respondents had a higher rate of ACEs, were more likely to experience specific ACEs, and to meet diagnostic requirements for MDD, GAD, and CPTSD than U.S. respondents. Emotional neglect was more strongly related to mental health than all other ACEs, and there was an exceptionally strong dose-response association between ACEs and CPTSD.

Conclusions
ACEs seem to be more common in Ireland than the U.S., and efforts to minimize exposure to ACEs through public policies may lead to beneficial mental health effects.

Full text

Child Abuse & Neglect 129 (2022) 105681
Available online 26 May 2022
0145-2134/© 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/).
The occurrence and co-occurrence of ACEs and their relationship
to mental health in the United States and Ireland
Christa McCutchen
a
,
*
, Philip Hyland
a
, Mark Shevlin
b
, Maryl`
ene Cloitre
c
,
d
a
Maynooth University, Department of Psychology, Kildare, Ireland
b
Ulster University, School of Psychology, Derry, Northern Ireland, United Kingdom of Great Britain and Northern Ireland
c
National Center for PTSD Dissemination and Training Division, VA Palo Alto Health Care System, Palo Alto, CA, USA
d
Department of Psychiatry and Behavioural Sciences, Stanford University, Stanford, CA, USA
ARTICLE INFO
Keywords:
ACEs
Mental health
Depression
Anxiety
PTSD
CPTSD
ABSTRACT
Background: Adverse childhood experiences (ACEs) have various deleterious effects on mental
health but few studies have been conducted in Ireland.
Objective: The primary objective was to determine if there were signicant differences in occur-
rences of ACEs in U.S. and Irish adults. We also sought to determine if there were unique asso-
ciations between individual and multiple ACE events and mental health.
Participants and setting: Preexisting nationally representative adult samples from the U.S. (n =
1893) and Ireland (n =1020) were utilized for analysis.
Method: To determine if there were signicant differences in the occurrence of specic ACE events
and the mean number of ACEs experienced by U.S. and Irish adults, chi-square difference tests
and an independent samples t-test were used, respectively. Binary logistic regression was used to
examine the unique associations between ACE events and major depressive disorder (MDD),
generalized anxiety disorder (GAD), posttraumatic stress disorder (PTSD), and Complex PTSD
(CPTSD). Nationality, sex, age, and educational level were included as covariates and adjusted
odds ratios are reported.
Results: Irish respondents had a higher rate of ACEs, were more likely to experience specic ACEs,
and to meet diagnostic requirements for MDD, GAD, and CPTSD than U.S. respondents. Emotional
neglect was more strongly related to mental health than all other ACEs, and there was an
exceptionally strong dose-response association between ACEs and CPTSD.
Conclusions: ACEs seem to be more common in Ireland than the U.S., and efforts to minimize
exposure to ACEs through public policies may lead to benecial mental health effects.
1. Introduction
The topic of childhood adversities and their deleterious effects on adult health and wellbeing has garnered a great deal of interest
over the past two decades. The seminal Adverse Childhood Experiences (ACE) Study, conducted in the United States of America (U.S.)
by the Kaiser Permanente health care organization and the Centers for Disease Control, revealed dose-response relationships between
ACEs and multiple health risk factors including leading causes of death such as heart disease, chronic lung disease and cancer (Felitti
et al., 1998). In general, there is a consensus that ACEs consist of the three categories included in the original study: abuse (verbal,
* Corresponding author at: Department of Psychology, John Hume Building, Maynooth University, Kildare, Ireland.
E-mail address: christa.mccutchen.2022@mumail.ie (C. McCutchen).
Contents lists available at ScienceDirect
Child Abuse & Neglect
journal homepage: www.elsevier.com/locate/chiabuneg
https://doi.org/10.1016/j.chiabu.2022.105681
Received 1 August 2021; Received in revised form 5 May 2022; Accepted 19 May 2022

Child Abuse & Neglect 129 (2022) 105681
2
physical, and sexual), neglect (emotional and physical), and household dysfunction (witnessed domestic violence, parents separated or
divorced, an alcoholic household member, a mentally ill/attempted suicide household member, and a household member in prison).
Since the original ACE study, there has been an abundance of research regarding ACEs in the U.S., and a growing body internationally
(Bellis et al., 2014; Riedl et al., 2020; Subramaniam et al., 2020). Numerous studies with representative samples have been conducted
in the U.S. to estimate the occurrence of ACEs in the population. A recent large-scale study (N =214,157) found that 62% of the U.S.
adult population had experienced at least one ACE event (Merrick et al., 2018).
There are limited data available regarding the occurrence of ACEs in the general population of the Republic of Ireland. Using data
from the Growing up in Ireland longitudinal cohort study of Irish youths between nine and thirteen years of age, Gardner et al. (2019)
reported that 73% had experienced one or more ACE. However, these data are limited by virtue of the fact that ACEs were measured
using 14 items, and of which, only four were from the original ACE questionnaire. Items regarding abuse and neglect were omitted, and
items related to bereavement, illness, and moving were included. Data from the Irish Longitudinal Study on Ageing (TILDA), a na-
tionally representative longitudinal study of adults aged 50 and older, found that 23.7% had experienced an ACE (Ward et al., 2020).
Consequently, it is currently unknown what proportion of the general adult population of Ireland have experienced one or more ACEs
in their lifetime. There are some cultural events and factors that suggest that ACEs may be relatively high in Ireland. For example,
based on sales data, Ireland was in the top ten countries found to have the highest consumption rates of alcohol (over 11 l per person,
per year; OECD, 2019). There have also been widely documented clerical and institutional abuses that occurred over decades (Carr
et al., 2010). Moreover, evidence suggests that mental disorders in Ireland may be relatively high, as reported in a study spanning 26
European countries (OECD, 2017). Ireland was found to have a 12.1% self-reported depression rate which was the fourth highest of the
countries included in the study, and considerably higher than the European average of 7.9%.
Overexposure to stressful life events such as ACEs will likely have formational impacts on the developing brain leading to mal-
adaptive behaviors and symptoms of trauma related mental illness such as depression, anxiety, and posttraumatic stress (Pelcovitz
et al., 2000). Numerous studies have connected traumatic stress to symptoms of depression and anxiety (Anda et al., 2002; Dube et al.,
2001; Friedman et al., 2002). Anda et al. (2006) found that those who experience four or more ACEs have a 49% increased risk of
developing depressive symptoms and a 19% increased risk of developing symptoms of anxiety. Previous research has also shown that
emotional abuse is most strongly related to depression, and sexual or physical abuse is most strongly related to anxiety (Friedman et al.,
2002; Mandelli et al., 2015). According to Kessler et al. (2010), ACEs account for 29.8% of mental health disorders across the world.
Few studies have compared the occurrence and mental health correlates of ACEs across different nations/cultures. To better un-
derstand the occurrences of ACEs, we set out in this study to compare the rates of ACEs and their associations with common mental
health problems using nationally representative data from the U.S. and Ireland. The U.S. and Ireland are similar in that they share
commonalities such as language, government type (i.e., democratic/republic), and economic relationships (e.g., international trade,
foreign investments, U.S. multinational companies), while also being culturally and geographically distinct from one another (e.g.,
size/population, diversity, and history). Several study objectives were formulated. First, we sought to determine if there were sig-
nicant differences in the occurrence of individual ACE events, and overall levels of ACE exposure, in U.S. and Irish adults. Second, we
examined if there were unique associations between each ACE event and different mental health variables including meeting diag-
nostic criteria for major depressive disorder (MDD), generalized anxiety disorder (GAD), posttraumatic stress disorder (PTSD), and
complex PTSD (CPTSD). Finally, we assessed if there was a dose-response association between the number of ACEs experienced and
each mental health disorder.
2. Method
2.1. Participants and procedures
2.1.1. U.S. sample
The U.S. data were collected as part of a project to assess the construct validity of PTSD and CPTSD for the 11th version of the
International Classication of Diseases (ICD-11) in March 2017 (see Cloitre et al., 2019). This nationally representative sample of non-
institutionalized adults was collected using an existing online research panel through a market research company called Growth from
Knowledge (GfK). The panel was randomly recruited through probability-based sampling and representative of the entire U.S. pop-
ulation. Of the 3953 people contacted, 1893 met the inclusion criteria which included those between 18 and 70 years of age who had
experienced at least one traumatic event in their lifetime. Due to an increased likelihood of experiencing traumatic events and higher
rates of trauma related diagnoses, women and racial minority groups were intentionally oversampled, both at a 2:1 ratio. The data
were then weighted to adjust for oversampling to establish a sample representative of the entire U.S. adult population. Ethical approval
was provided by the Research Ethics Committee at the National College of Ireland. Participants were compensated by GfK for their
participation in the panel. The median completion time was 18 min and informed consent was obtained before survey completion.
2.1.2. Irish sample
A nationally representative sample of non-institutionalized Irish adults aged 18 years and older was collected in February 2019 by a
survey research company called Qualtrics. Quota sampling methods were used to construct a non-probability-based sample that was
representative of the general adult population in terms of sex, age, and geographical distribution (Hyland et al., 2021). These three
sample characteristics match known population parameters as per the 2016 Irish census data (Central Statistics Ofce, 2020). The
number of people contacted was not gathered therefore it was impossible to determine a participation rate; however, the nal sample
included 1020 participants. Those who chose to participate were provided detailed information about the study prior to their
C. McCutchen et al.

Child Abuse & Neglect 129 (2022) 105681
3
participation and ethical approval was provided by the Social Research Ethics Committee at Maynooth University, Ireland. Partici-
pants were remunerated for their time by Qualtrics. The median completion time was 22 min. Sociodemographic details for the U.S.
and Irish samples are presented in Table 1. Sociodemographic details that were included in the samples but were not used for analysis
can be found in Supplementary Table 1.
2.1.3. Measures
2.1.3.1. ACEs. The U.S. and Irish samples completed the Adverse Childhood Experiences questionnaire (ACE-Q; Felitti et al., 1998)
which measures exposure to ten events occurring before the age of 18 (see Fig. 1 for a description of each event). All items were
answered on a ‘Yes’ (1) or ‘No’ (0) basis. The measure is widely used and multiple studies with adult samples have demonstrated that
the ACE-Q produces reliable and valid scale scores (Dube et al., 2004; Ford et al., 2014; Murphy et al., 2014; Wingenfeld et al., 2011).
2.1.3.2. MDD. The Patient Health Questionnaire-9 (PHQ-9; Kroenke et al., 2001) was used to measure MDD in the Irish sample, while
the eight-item version of the PHQ (Kroenke et al., 2009) was used in the U.S. sample. The PHQ-9 differs from the PHQ-8 in that it
includes one item measuring suicidality/self-harm. To ensure consistency across the two samples, we removed item 9 from the Irish
sample for all analyses. Respondents indicated how often they have been bothered by each symptom over the last two weeks using a
four-point Likert scale ranging from 0 (‘Not at all’) to 3 (‘Nearly every day’). Scores range from 0 to 24, and a score of 10 or above is
indicative of a probable MDD diagnosis (Kroenke et al., 2001, 2009). The PHQ-8 has demonstrated excellent psychometric properties
(Manea et al., 2015; Wu et al., 2020), and the internal reliability (Cronbach's alpha) of the scale scores were excellent in the Irish (
α
=
0.90) and U.S. (
α
=0.93) samples.
2.1.3.3. GAD. The Generalized Anxiety Disorder 7-item Scale (GAD-7; Spitzer et al., 2006) was used to measure GAD symptoms in
both samples. Respondents indicated how often they have been bothered by each symptom over the last two weeks using a four-point
Likert scale ranging from 0 (‘Not at all’) to 3 (‘Nearly every day’). Scores range from 0 to 21 with higher scores reecting higher
symptomology. A score of 10 or above is indicative of a probable GAD diagnosis (Spitzer et al., 2006). The psychometric properties of
the GAD-7 have been shown to be excellent in prior adult samples (Kertz et al., 2013), and the internal reliability of the scale scores
were excellent in the Irish (
α
=0.91) and U.S. (
α
=0.94) samples.
2.1.3.4. PTSD and CPTSD. The International Trauma Questionnaire (ITQ: Cloitre et al., 2018) was used to measure symptoms of PTSD
and CPTSD in the U.S. and Irish samples. The ITQ includes six items measuring PTSD symptoms across the three symptom clusters of
Re-experiencing in the here and now, Avoidance, and Sense of Current Threat, and six items measuring Disturbances in Self-
Organization (DSO) symptoms across the three clusters of Affective Dysregulation, Negative Self-Concept, and Disturbed Relation-
ships. All items are answered in relation to the participant's most distressing traumatic life event. Respondents indicate how much they
have been bothered by each PTSD symptom during the past month and how they typically feel, think about oneself, and relate to others
for each DSO symptom. In addition, there are three items measuring functional impairment for both sets of symptoms. Functional
impairments are in the areas of social, occupational/educational, and other important areas of life. A ve-point Likert scale ranging
from 0 (Not at all) to 4 (Extremely) is used for each item and when a response is ≥2 (Moderately) on the Likert scale, the symptom is
considered to be present (Cloitre et al., 2018). The psychometric properties of the ITQ scores have been supported in general popu-
lation samples and the internal reliability scale scores in the U.S. sample for PTSD (
α
=0.89), DSO (
α
=0.89), and total (
α
=0.92) were
Table 1
Sociodemographic included in analysis.
Ireland U.S.
n =1020 n =1839
% (n) % (n)
Sex
Male 49.0 (500) 48.0 (883)
Female 51.0 (520) 52.0 (956)
Age in years
18–24 12.3 (125) 10.0 (184)
25–34 20.2 (206) 20.7 (382)
35–44 23.5 (240) 19.0 (350)
45–54 19.1 (195) 18.5 (339)
55–64 14.1 (144) 21.6 (398)
65+10.8 (110) 10.2 (187)
Age M =43.10, SD =15.12 M =44.55, SD =14.89
Highest educational attainment
Did not complete secondary school 7.1 (72) 9.1 (168)
Completed secondary school 39.2 (400) 48.4 (891)
Completed an undergraduate university degree 36.9 (376) 30.3 (558)
Completed a postgraduate university degree 16.9 (172) 12.1 (223)
C. McCutchen et al.

Child Abuse & Neglect 129 (2022) 105681
4
excellent as were the scale scores for the Irish sample for PTSD (
α
=0.91), DSO (
α
=0.93), and total (
α
=0.95). Exposure to a traumatic
event, the presence of at least one symptom from each PTSD cluster, and at least one indicator of functional impairment associated
with these symptoms are required for a PTSD diagnosis. At least one symptom from each DSO cluster, at least one indicator of
functional impairment associated with these symptoms, and all of the PTSD criteria must be present for a CPTSD diagnosis. According
to the ICD-11 diagnostic rules, an individual cannot receive a diagnosis of both PTSD and CPTSD therefore if a person satises the
criteria for CPTSD they receive that diagnosis over a PTSD diagnosis.
2.2. Data analysis procedures
Chi-square (
χ
2
) difference tests were used to determine if there were signicant differences in the occurrence of any ACE exposure
and individual ACE events in U.S. and Irish adults. An independent samples t-test was used to determine if there was a signicant
difference in the mean number of ACEs experienced by U.S. and Irish adults. The magnitude of the mean differences was assessed using
Cohen's d, with values <0.5 indicating a small effect, values between 0.5 and 0.8 indicating a medium effect, and values >0.8
indicating a large effect.
To examine the unique associations between each ACE event and each mental health diagnosis (viz., MDD, GAD, PTSD, CPTSD),
and to examine if there was a dose-response relationship between number of ACEs (i.e., one, two, three, and four or more) and meeting
criteria for each mental health disorder, we used binary logistic regression (BLR) analyses. The U.S. and Irish samples were combined
for these analyses, and nationality (0 =U.S., 1 =Irish), sex (0 =males, 1 =females), age, and educational level (0 =did not nish
high/secondary school, 1 =nished high/secondary school, 2 =completed an undergraduate university degree, and 3 =completed a
postgraduate university degree) were included as covariates. To evaluate the dose-response relationships, ACE scores were recoded
into a categorical variable (0 =no ACE event, 1 =one ACE, 2 =two ACEs, 3 =three ACEs, 4 =four or more ACEs). Missing data ranged
from 2.6% to 5.2% and handled by the default listwise deletion option in SPSS for BLR. Adjusted odds ratios (AOR) are reported.
3. Results
3.1. Comparing occurrences
Frequencies of ACEs based on nationality are presented in Fig. 1. Several signicant differences between Irish and U.S. respondents
were found. More than half of the Irish (65.2%) and U.S. (61.1%) adults had experienced at least one ACE event, and Irish respondents
were signicantly more likely to have experienced at least one ACE than U.S. respondents (
χ
2
(1) =4.56, p =.033, OR =1.19 [95% CI
=1.01, 1.40]). Irish respondents were also signicantly more likely than U.S. respondents to have experienced verbal abuse (35.5% vs
Fig. 1. Frequencies of ACEs based on nationality.
Note. *p <.001.
C. McCutchen et al.

Child Abuse & Neglect 129 (2022) 105681
5
21.3%,
χ
2
(1) =68.11, p <.001, OR =2.04 [95% CI =1.71, 2.41]), physical abuse (27.1% vs 15.7%,
χ
2
(1) =62.93, p <.001, OR =
2.10 [95% CI =1.74, 2.53]), emotional neglect (30.2% vs 17.0%,
χ
2
(1) =66.63, p <.001, OR =2.1 [95% CI =1.76, 2.52]), physical
neglect (10.2% vs 5.4%,
χ
2
(1) =23.35, p <.001, OR =2.01 [95% CI =1.51, 2.68]), and mentally ill/suicidal household member
(22.5% vs 15.5%,
χ
2
(1) =21.57, p <.001, OR =1.58 [95% CI =1.30, 1.92]). U.S. respondents were signicantly more likely than
Irish respondents to have separated/divorced parents (33.5% vs 19.5%,
χ
2
(1) =62.62, p <.001, OR =0.48 [95% CI =0.40, 0.58]).
Additionally, a statistically signicant difference was found between the mean number of ACEs in the Irish (M =2.08, SD =2.32)
and U.S. (M =1.70, SD =2.10) samples, however, the effect size was small (t (2804) = − 4.36, p <.001, d =0.17).
3.2. Associations between ACEs and mental health diagnoses
The AORs for the associations between individual ACEs, along with sociodemographic factors, and meeting diagnostic re-
quirements for MDD, GAD, PTSD, and CPTSD are reported in full in Table 2.
The BLR models for MDD (
χ
2
(16, 2711) =562.94, p <.001), GAD (
χ
2
(16, 2716) =464.02, p <.001), PTSD (
χ
2
(16, 2784) =
115.78, p <.001), and CPTSD (
χ
2
(16, 2784) =231.60, p <.001) were all statistically signicant. Regarding associations between
individual ACEs and meeting diagnostic requirements, irrespective of sociodemographic factors, four events were signicantly
associated with MDD: verbal abuse (AOR =1.90, p <.001), sexual abuse (AOR =2.10, p <.001), emotional neglect (AOR =2.49, p <
.001), and a mentally ill/attempted suicide household member (AOR =2.14, p <.001). The same ACE events were found to be
signicantly associated with GAD: verbal abuse (AOR =1.87, p <.001), sexual abuse (AOR =1.98, p <.001), emotional neglect (AOR
=2.24, p <.001), and a mentally ill/attempted suicide household member (AOR =1.90, p <.001), with the addition of witnessed
domestic violence (AOR =1.49, p =.028). Signicant associations were found between PTSD and three ACE events: emotional neglect
(AOR =2.03, p =.007), problem drinker in household (AOR =1.71, p =.028), and household member in prison (AOR =1.94, p =
.022). Finally, ve ACE events were signicantly associated with CPTSD: sexual abuse (AOR =3.06, p <.001), emotional neglect
(AOR =1.69, p =.021), witnessed domestic violence (AOR =1.69, p =.030), problem drinker in household (AOR =1.91, p =.002),
and a mentally ill/attempted suicide household member (AOR =1.71, p =.010). A graphical representation of these results can be
found in Fig. 2.
Other notable results from these analyses were that Irish respondents were signicantly more likely than U.S. respondents to meet
diagnostic requirements for MDD, GAD, and CPTSD, irrespective of all other factors in the model. Females were signicantly more
likely to meet diagnostic criteria MDD, GAD, and PTSD than males. Younger age was signicantly associated with meeting re-
quirements for all four diagnoses. And nally, higher educational attainment was associated with a reduced risk of meeting diagnostic
requirements for MDD and GAD (see Table 2 for full details).
Table 2
Binary logistic regression results for each mental health disorder.
MDD GAD PTSD CPTSD
AOR 95% CI AOR 95% CI AOR 95% CI AOR 95% CI
Nationality
U.S. 0
a
Ireland 1.98*** 1.58–2.49 2.09*** 1.63–2.68 1.09 0.72–1.67 1.61* 1.10–2.36
Sex
Male 0
a
Female 1.47*** 1.18–1.84 1.81*** 1.41–2.33 1.76* 1.14–2.71 1.02 0.69–1.50
Age 0.97*** 0.97–0.98 0.98*** 0.96–0.98 0.96*** 0.95–0.98 0.98*** 0.96–0.99
Education
Not secondary 0
a
Secondary school 0.66* 0.46–0.96 0.56** 0.38–0.82 1.41 0.65–3.07 1.03 0.54–1.97
Undergraduate 0.50*** 0.34–0.74 0.43*** 0.28–0.64 1.06 0.47–2.39 0.94 0.48–1.83
Postgraduate 0.38*** 0.24–0.60 0.30*** 0.18–0.50 2.17 0.093–5.07 0.94 0.44–2.03
ACE events
Verbal abuse 1.88*** 1.14–2.56 1.87*** 1.35–2.59 1.24 0.70–2.17 1.54 0.93–2.55
Physical abuse 0.89 0.65–1.21 0.74 0.53–1.03 1.04 0.60–1.78 1.46 0.92–2.33
Sexual abuse 1.97*** 1.51–2.58 1.98*** 1.45–2.63 1.40 0.87–2.23 3.06*** 2.06–4.54
Emotional neglect 2.48*** 1.91–3.23 2.24*** 1.68–2.99 2.03** 1.22–3.37 1.69* 1.08–2.64
Physical neglect 1.19 0.82–1.74 0.97 0.65–1.45 1.73 0.96–3.10 1.13 0.69–1.87
Separation/divorce 0.90 0.70–1.16 1.01 0.77–1.33 0.98 0.62–1.53 0.68 0.45–1.04
Witness DV 0.98 0.69–1.37 1.49* 1.05–2.13 0.96 0.54–1.73 1.69* 1.05–2.72
Problem drinker 1.29 1.00–1.67 1.10 0.83–1.47 1.71* 1.06–2.75 1.91** 1.26–2.89
Mentally ill/AS 2.11*** 1.64–2.73 1.90*** 1.44–2.51 0.73 0.44–1.21 1.71* 1.14–2.56
Prison 1.17 0.80–1.71 1.10 0.74–1.63 1.94* 1.10–3.43 0.94 0.54–1.63
*
p <.05.
**
p <.01.
***
p <.001.
a
This parameter is set to zero because it is redundant.
C. McCutchen et al.

Child Abuse & Neglect 129 (2022) 105681
6
3.3. Dose-response associations
The BLR models evaluating the dose-response associations between number of ACEs (one event, two events, three events, and four
or more events) and meeting diagnostic criteria, were statistically signicant across the four diagnoses: MDD (
χ
2
(10, 2711) =485.62,
p <.001), GAD (
χ
2
(10, 2302) =400.70, p <.001), PTSD (
χ
2
(10, 2784) =103.12, p <.001), and CPTSD (
χ
2
(10, 2784) =174.08, p <
.001). There was evidence of a dose-response association for all four diagnoses with the strength of the association increasing at each
level of ACE exposure. Statistically signicant associations were found between: MDD and one (AOR =2.35, p <.001), two (AOR =
3.50, p <.001), three (AOR =5.87, p <.001), and ≥four (AOR =9.25, p <.001) ACE events; GAD and one (AOR =2.11, p <.001), two
Fig. 2. Associations between each ACE event and mental health outcomes when controlling for nationality, age, sex, and highest level of education.
Fig. 3. Dose response associations between number of ACEs and mental health outcomes.
C. McCutchen et al.

Child Abuse & Neglect 129 (2022) 105681
7
(AOR =3.41, p <.001), three (AOR =3.93, p <.001), and ≥four (AOR =7.80 p <.001) ACE events; CPTSD and one (AOR =2.70, p =
.011), two (AOR =3.11, p =.007), three (AOR =7.97, p <.001), and ≥four (AOR =15.70 p <.001) ACE events. The dose-response
associations between ACE levels and PTSD were signicant with the exception of one ACE event (AOR =1.95, p =.064). Statistically
signicant dose-response associations were found between PTSD and two (AOR =2.78, p =.005), three (AOR =3.08, p <.004), and
≥four (AOR =6.47 p <.001) ACE events. Graphical representation of these results can be found in Fig. 3.
4. Discussion
The primary aim of this study was to better understand the occurrence of ACEs and their association with common mental health
problems in the U.S. and Ireland. We found that Irish adults were signicantly more likely than U.S. adults to experience an ACE and
had a higher mean number of ACEs. We also found statistically signicant associations between meeting criteria for each diagnosis and
various individual ACEs. Emotional neglect was the only ACE event signicantly associated with all four diagnoses and those who
experienced emotional neglect were approximately two- to two-and-a-half times more likely to meet requirements for each disorder.
Additionally, living with someone with a mental illness or attempted suicide, and sexual abuse, were signicantly associated with
MDD, GAD, and CPTSD. The ACEs that were signicantly associated with PTSD were emotional neglect (shared among all four di-
agnoses), having a problem drinker in the household (shared only with CPTSD), and having a household member in prison. Finally, we
found a statistically signicant dose-response relationship for all four diagnoses however CPTSD had a much greater likelihood of
occurrence as the number of ACE events increased.
To our knowledge, this study was not only the rst to directly compare ACEs in the U.S. and Ireland but it is also the rst study to
examine ACEs from a nationally representative adult sample from Ireland. We found that 61% of U.S. adults had experienced at least
one ACE event which is in line with another large-scale study conducted in the U.S. that reported that 62% of the U.S. adult population
had experienced at least one ACE event (Merrick et al., 2018). Additionally, we found that 65% of Irish adults had experienced at least
one ACE. This evidence suggests that the rate of ACEs in Ireland is likely to be much higher than the 24% of respondents who had
experiences at least one ACE reported from the TILDA study which used a sample of participants aged 50 and older (Ward et al., 2020).
This evidence also suggests that the rate of ACEs is much lower than the 73% reported using the Growing up in Ireland study which had
a sample of youths between nine and thirteen years of age and measured ACEs using a questionnaire that contained 14 items, four of
which were from the original ACE questionnaire (Gardner et al., 2019). Additionally, Irish respondents were just over two times more
likely than U.S. respondents to have experienced four of the ve abuse and neglect items (viz., verbal abuse, physical abuse, emotional
neglect, and physical neglect) and having a household member who had a mental illness or attempted suicide. Respondents from the U.
S. were signicantly more likely to have experienced parental separation or divorce. This latter nding may be due to a cultural
difference between Ireland and the U.S. which is that divorce was only legalised in Ireland in 1996 while it has been legal in the U.S.
since as far back as the 19th century.
Another unique aspect of this study is that we isolated the predictor variables to evaluate outcomes regardless of sociodemographic
factors as well as other ACEs. In doing so, we found additional information regarding differences between adults in the U.S. and
Ireland. We found that Irish respondents were approximately two times more likely than U.S. respondents to meet diagnostic re-
quirements for MDD, GAD, and CPTSD, irrespective of all other factors. This is somewhat consistent with the Organization for Eco-
nomic Co-operation and Development (OECD, 2017) report which reported that Ireland was found to have a 12.1% depression rate
while Cao et al. (2020), found that the rate in the U.S. was 8%. However, the central purpose of isolating predictor variables was to
analyse the associations between the individual ACE events and diagnostic outcomes when removing the possible inuence of other
factors.
Our analysis of ACEs and diagnostic outcomes revealed some particularly notable ndings. The signicant associations between
emotional neglect and all four diagnoses highlight the toxic nature of emotional neglect. Verbal abuse and emotional neglect were the
most prevalent ACEs in the Irish sample which is similar to the ndings from a sample of Irish university students (Corcoran &
McNulty, 2018). However, verbal abuse was not signicantly associated with PTSD or CPTSD. Pietrek et al. (2013) found that
emotional neglect had greater associations with MDD as well as schizophrenia, and borderline personality disorder than physical
punishment, sexual abuse, and general trauma. Additionally, Green et al. (2010) found that those who experiences emotional neglect
were nearly two times more likely to abuse substances which was second only to those whose parents suffered from substance abuse.
Emotional neglect has been found to cause low oxytocin levels and is associated with insecure attachment which, among other issues,
impacts one's ability to form relationships (Müller et al., 2019). Survival insecurity due to a lack of caregiver attachment, resulting in
social dysfunction, may explain the associations between emotional neglect and all four diagnoses. It is important to raise awareness of
these associations in adults that are in positions to observe signs of emotional neglect in a child (e.g., teachers, neighbours) which may
promote the reporting of cases to the proper authorities.
Other notable ndings relate to PTSD and CPTSD. In the recent revision of the ICD-11, the PTSD diagnosis was updated and CPTSD
was introduced. This study is the rst to evaluate dose-response relationships between ACEs and the ICD-11 versions of PTSD and
CPTSD. The substantially increased likelihood of meeting criteria for CPTSD (nearly 16 times) when experiencing four or more ACE
events is particularly noteworthy. Additionally, we found that the strongest unique association for all predictors and all outcomes was
between CPTSD and sexual abuse in which respondents were just over three times more likely to meet diagnostic requirements for
CPTSD. This association is consistent with other empirical ndings (e.g., Hyland et al., 2017).
Several limitations should be considered regarding these ndings. First, the survey was conducted using self-report measures which
may limit the precision of the responses and therefore replication with clinician-administered interviews would be benecial. Second,
the surveys were collected at separate times and were not designed for the specic purpose of cross-country comparisons meaning that
C. McCutchen et al.

Child Abuse & Neglect 129 (2022) 105681
8
only a small number of covariates could be included as they were common across both surveys. Third, additional potentially traumatic
events that may have occurred outside of the home such as bullying or community violence were not included in this study and may
have played a role in the mental health variables. Future research should include additional adversities that may occur during
childhood.
In summation, the main ndings from this study were: (1) Irish respondents had a slightly higher rate of ACEs than U.S. re-
spondents, and were more likely to experience numerous detrimental ACEs, and were more likely to meet diagnostic requirements for
MDD, GAD, and CPTSD; (2) CPTSD had strong associations with ve ACEs and had an exceptionally strong dose-response relationship
when experiencing four or more ACE events; (3) while it may be assumed to be a less acute ACE than abuse items, emotional neglect
had a stronger association with mental health than all other ACEs. While the complete eradication of ACE events may not be feasible,
efforts to minimize exposure to ACEs through public policies will likely have a positive effect on population mental health.
Supplementary data to this article can be found online at https://doi.org/10.1016/j.chiabu.2022.105681.
Ethical standards
The authors assert that all procedures contributing to this work comply with the ethical standards of the relevant national and
institutional committee on human experimentation with the Helsinki Declaration of 1975, as revised in 2008. Informed consent was
obtained, and ethical approval was provided by an ethics committee.
Financial support
This research did not receive any specic grant from funding agencies in the public, commercial, or not-for-prot sectors.
Data availability statement
The data are available upon request to the corresponding author.
Declaration of competing interest
Maryl`
ene Cloitre participated as a member of the World Health Organization Working Group on the Classication of Disorders
Specically Associated with Stress, reporting to the International Advisory Group for the Revision of ICD-10 Mental and Behavioural
Disorders. However, the views expressed reect the opinions of the authors and not necessarily the Working Group or Advisory Group
and the content of this article does not represent WHO policy.
References
Anda, R. F., Felitti, V. J., Bremner, J. D., Walker, J. D., Whiteld, C. H., Perry, B. D., Dube, S. R., & Giles, W. H. (2006). The enduring effects of abuse and related
adverse experiences in childhood. European Archives of Psychiatry and Clinical Neuroscience, 256(3), 174–186.
Anda, R. F., Whiteld, C. L., Felitti, V. J., Chapman, D., Edwards, V. J., Dube, S. R., & Williamson, D. F. (2002). Adverse childhood experiences, alcoholic parents, and
later risk of alcoholism and depression. Psychiatric Services (Washington, D.C.), 53(8), 1001–1009. https://doi.org/10.1176/appi.ps.53.8.1001
Bellis, M. A., Hughes, K., Leckenby, N., Jones, L., Baban, A., Kachaeva, M., Povilatis, R., Pudule, I., Qirjako, G., Ulukol, B., Raleva, M., & Terzic, N. (2014). Adverse
childhood experiences and associations with health-harming behaviours in young adults: Surveys in eight eastern European countries. Bulletin of the World Health
Organization, 92, 641–655.
Cao, C., Hu, L., Xu, T., Liu, Q., Koyanagi, A., Yang, L., Carvalho, A. F., Cavazos-Rehg, P. A., & Smith, L. (2020). Prevalence, correlates and misperception of depression
symptoms in the United States, NHANES 2015–2018. Journal of Affective Disorders, 269, 51–57.
Carr, A., Dooley, B., Fitzpatrick, M., Flanagan, E., Flanagan-Howard, R., Tierney, K., White, M., Margaret, D., & Egan, J. (2010). Adult adjustment of survivors of
institutional child abuse in Ireland. Child Abuse & Neglect, 34(7), 477–489.
Central Statistics Ofce. (2020). Census 2016 reports. Retrieved from https://www.cso.ie/en/census/census2016reports/.
Cloitre, M., Hyland, P., Bisson, J. I., Brewin, C. R., Roberts, N. P., Karatzias, T., & Shevlin, M. (2019). ICD-11 posttraumatic stress disorder and complex posttraumatic
stress disorder in the United States: A population-based study. Journal of Traumatic Stress, 32(6), 833–842. https://doi.org/10.1002/jts.22454
Cloitre, M., Shevlin, M., Brewin, C. R., Bisson, J. I., Roberts, N. P., Maercker, A., Karatzias, T., & Hyland, P. (2018). The international trauma questionnaire:
Development of a self-report measure of ICD-11 PTSD and complex PTSD. Acta Psychiatrica Scandinavica, 138, 536–546. https://doi.org/10.1111/acps.12956
Corcoran, M., & McNulty, M. (2018). Examining the role of attachment in the relationship between childhood adversity, psychological distress and subjective well-
being. Child Abuse & Neglect, 76, 297–309. https://doi.org/10.1016/j.chiabu.2017.11.012
Dube, S. R., Anda, R. F., Felitti, V. J., Chapman, D. P., Williamson, D. F., & Giles, W. H. (2001). Childhood abuse, household dysfunction, and the risk of attempted
suicide throughout the life span: Findings from the adverse childhood experiences study. JAMA, 286(24), 3089–3096.
Dube, S. R., Williamson, D. F., Thompson, T., Felitti, V. J., & Anda, R. F. (2004). Assessing the reliability of retrospective reports of adverse childhood experiences
among adult HMO members attending a primary care clinic. Child Abuse & Neglect, 28(7), 729–737. https://doi.org/10.1016/j.chiabu.2003.08.009
Felitti, V. J., Anda, R. F., Nordenberg, D., Williamson, D. F., Spitz, A. M., Edwards, V., Koss, M. P., & Marks, J. S. (1998). Relationship of childhood abuse and
household dysfunction to many of the leading causes of death in adults: The adverse childhood experiences (ACE) study. American Journal of Preventive Medicine,
14(4), 245–258. https://doi.org/10.1016/S0749-3797(98)00017-8
Ford, D. C., Merrick, M. T., Parks, S. E., Breiding, M. J., Gilbert, L. K., Edwards, V. J., Dhingra, S. S., Barile, J. P., & Thompson, W. W. (2014). Examination of the
factorial structure of adverse childhood experiences and recommendations for three subscale scores. Psychology of Violence, 4(4), 432–444. https://doi.org/
10.1037/a0037723
Friedman, S., Smith, L., Fogel, D., Paradis, C., Viswanathan, R., Ackerman, R., & Trappler, B. (2002). The incidence and inuence of early traumatic life events in
patients with panic disorder: A comparison with other psychiatric outpatients. Journal of Anxiety Disorders, 16(3), 259–272.
Gardner, R., Feely, A., Layte, R., Williams, J., & McGavock, J. (2019). Adverse childhood experiences are associated with an increased risk of obesity in early
adolescence: A population-based prospective cohort study. Pediatric Research, 86(4), 522–528.
C. McCutchen et al.

Child Abuse & Neglect 129 (2022) 105681
9
Green, J. G., McLaughlin, K. A., Berglund, P. A., Gruber, M. J., Sampson, N. A., Zaslavsky, A. M., & Kessler, R. C. (2010). Childhood adversities and adult psychiatric
disorders in the national comorbidity survey replication I: Associations with rst onset of DSM-IV disorders. Archives of General Psychiatry, 67(2), 113–123.
https://doi.org/10.1001/archgenpsychiatry.2009.186
Hyland, P., Murphy, J., Shevlin, M., Valli`
eres, F., McElroy, E., Elklit, A., Christoffersen, M., & Cloitre, M. (2017). Variation in post-traumatic response: The role of
trauma type in predicting ICD-11 PTSD and CPTSD symptoms. Social Psychiatry and Psychiatric Epidemiology, 52, 727–736. https://doi.org/10.1007/s00127-017-
1350-8
Hyland, P., Valli`
eres, F., Cloitre, M., Ben-Ezra, M., Karatzias, T., Olff, M., Murphy, J., & Shevlin, M. (2021). Trauma, PTSD, and complex PTSD in the Republic of
Ireland: Prevalence, service use, comorbidity, and risk factors. Social Psychiatry and Psychiatric Epidemiology, 56(4), 649–658.
Kertz, S., Bigda-Peyton, J., & Bjorgvinsson, T. (2013). Validity of the generalized anxiety disorder-7 scale in an acute psychiatric sample. Clinical Psychology &
Psychotherapy, 20, 456–464. https://doi.org/10.1002/cpp.1802
Kessler, R. C., McLaughlin, K. A., Green, J. G., Gruber, M. J., Sampson, N. A., Zaslavsky, A. M., Aguilar-Gaxiola, S., Alhamzami, A. O., Alonso, J., Angermeyer, M.,
Beniet, C., Bromet, E., Charrerji, S., de Girolamo, G., Demyttenaere, K., Fayyad, J., Florescu, S., Gal, G., Gureje, O., & Williams, D. R. (2010). Childhood adversities
and adult psychopathology in the WHO world mental health surveys. The British Journal of Psychiatry, 197(5), 378–385.
Kroenke, K., Spitzer, R. L., & Williams, J. B. (2001). The PHQ-9: Validity of a brief depression severity measure. Journal of General Internal Medicine, 16, 606–613.
https://doi.org/10.1046/j.15251497.2001.016009606.x
Kroenke, K., Strine, T. W., Spitzer, R. L., Williams, J. B., Berry, J. T., & Mokdad, A. H. (2009). The PHQ-8 as a measure of current depression in the general population.
Journal of Affective Disorders, 114, 163–173. https://doi.org/10.1016/j.jad.2008.06.026
Mandelli, L., Petrelli, C., & Serretti, A. (2015). The role of specic early trauma in adult depression: a meta-analysis of published literature. Childhood trauma and
adult depression. European Psychiatry, 30(6), 665–680. Spitzer, R. L., First, M. B., & Wakeeld, J. C. (2007). Saving PTSD from itself in DSM-V. Journal of Anxiety
Disorders, 21(2), 233–241. doi:10.1016/j.janxdis.2006.09.006.
Manea, L., Gilbody, S., & McMillan, D. (2015). A diagnostic metaanalysis of the patient health Questionnaire-9 (PHQ-9) algorithm scoring method as a screen for
depression. General Hospital Psychiatry, 37, 67–75. https://doi.org/10.1016/j.genhosppsych.2014.09.009
Merrick, M. T., Ford, D. C., Ports, K. A., & Guinn, A. S. (2018). Prevalence of adverse childhood experiences from the 2011–2014 behavioral risk factor surveillance
system in 23 states. JAMA Pediatrics, 172(11), 1038–1044.
Müller, L. E., Bertsch, K., Bülau, K., Herpertz, S. C., & Buchheim, A. (2019). Emotional neglect in childhood shapes social dysfunctioning in adults by inuencing the
oxytocin and the attachment system: Results from a population-based study. International Journal of Psychophysiology, 136, 73–80.
Murphy, A., Steele, M., Dube, S. R., Bate, J., Bonuck, K., Meissner, P., Goldman, H., & Steele, H. (2014). Adverse childhood experiences (ACEs) questionnaire and adult
attachment interview (AAI): Implications for parent child relationships. Child Abuse & Neglect, 38(2), 224–233.
OECD: Organisation for Economic Co-operation and Development. (2019). Health at a glance 2019: OECD indicators. Retrieved from https://www.oecd-ilibrary.org/
sites/961753cf-en/index.html?itemId=/content/component/961753cf-en.
OECD: Organisation for Economic Co-operation and Development. (2017). Health at a glance 2017: OECD indicators. Retrieved from https://www.oecd-ilibrary.org/
social-issues-migration-health/health-at-a-glance-2017_health_glance-2017-en.
Pelcovitz, D., Kaplan, S. J., DeRosa, R. R., Mandel, F. S., & Salzinger, S. (2000). Psychiatric disorders in adolescents exposed to domestic violence and physical abuse.
American Journal of Orthopsychiatry, 70(3), 360–369.
Pietrek, C., Elbert, T., Weierstall, R., Müller, O., & Rockstroh, B. (2013). Childhood adversities in relation to psychiatric disorders. Psychiatry Research, 206(1),
103–110. https://doi.org/10.1016/j.psychres.2012.11.003
Riedl, D., Lampe, A., Exenberger, S., Nolte, T., Traw¨
oger, I., & Beck, T. (2020). Prevalence of adverse childhood experiences (ACEs) and associated physical and
mental health problems amongst hospital patients: Results from a cross-sectional study. General Hospital Psychiatry, 64, 80–86.
Spitzer, R. L., Kroenke, K., Williams, J. B., & Lowe, B. (2006). A brief measure for assessing generalized anxiety disorder: The GAD-7. Archives of Internal Medicine, 166,
1092–1097. https://doi.org/10.1001/archinte.166.10.1092
Subramaniam, M., Abdin, E., Seow, E., Vaingankar, J. A., Shae, S., Shahwan, S., Lim, M., Fung, D., James, L., Verma, S., & Chong, S. A. (2020). Prevalence, socio-
demographic correlates and associations of adverse childhood experiences with mental illnesses: Results from the Singapore mental health study. Child Abuse &
Neglect, 103, Article 104447.
Ward, M., Turner, N., Briggs, R., O'Halloran, A. M., & Kenny, R. A. (2020). Resilience does not mediate the association between adverse childhood experiences and
later life depression. Findings from the irish longitudinal study on ageing (TILDA). Journal of Affective Disorders, 277, 901–907.
Wingenfeld, K., Sch¨
afer, I., Terfehr, K., Grabski, H., Driessen, M., Grabe, H., L¨
owe, B., & Spitzer, C. (2011). Reliable, valid and economic recording of early trauma:
First psychometric characterization of the german version of the adverse childhood experiences questionnaire (ACE). PPmP psychotherapy Psychosomatics Medical
psychology, 61(01), e10–e14.
Wu, Y., Levis, B., Riehm, K. E., Saadat, N., Levis, A. W., Azar, M., Rice, D. B., Boruff, J., Cuijpers, P., Gilbody, S., Ioannidis, J. P. A., Kloda, L. A., McMillan, D.,
Patten, S. B., Shrier, I., Ziegelstein, R. C., Akena, D. H., Arroll, B., Ayalon, L., & Thombs, B. D. (2020). Equivalency of the diagnostic accuracy of the PHQ-8 and
PHQ-9: a systematic review and individual participant data meta-analysis. Psychological Medicine, 50(8), 1368–1380.
C. McCutchen et al.