INTRODUCTION
Conduct Disorder (CD) is a common disorder of childhood and adolescence, characterized by persistent aggressive and non-aggressive antisocial behaviors (
1American Psychiatric Association (2013): Diagnostic and Statistical Manual of Mental Disorders, 5th ed. Washington, DC: American Psychiatric Publishing.
). CD is associated with various negative outcomes including low educational achievement, poor mental and physical health, and antisocial personality disorder (
2- Bevilacqua L.
- Hale D.
- Barker E.D.
- Viner R.
Conduct problems trajectories and psychosocial outcomes: a systematic review and meta-analysis.
,
3- Copeland W.E.
- Shanahan L.
- Costello E.J.
- Angold A.
Childhood and adolescent psychiatric disorders as predictors of young adult disorders.
,
4- Erskine H.E.
- Norman R.E.
- Ferrari A.J.
- Chan G.C.K.
- Copeland W.E.
- Whiteford H.A.
- Scott J.G.
Long-term outcomes of attention-deficit/hyperactivity disorder and conduct disorder: a systematic review and meta-analysis.
). The resulting individual, familial, and societal burden (
5- Rivenbark J.G.
- Odgers C.L.
- Caspi A.
- Harrington H.
- Hogan S.
- Houts R.M.
- et al.
The high societal costs of childhood conduct problems: evidence from administrative records up to age 38 in a longitudinal birth cohort.
) highlights the importance of increasing our understanding of the pathophysiological mechanisms associated with CD to improve its prevention, assessment, and treatment.
In line with neurodevelopmental models, studies of CD have identified structural alterations in brain regions implicated in emotion processing, empathy, decision-making, reinforcement learning and social cognition, which are frequently impaired in CD youth (
6- Fairchild G.
- Hawes D.J.
- Frick P.J.
- Copeland W.E.
- Odgers C.L.
- Franke B.
- et al.
Conduct disorder.
). For example, two meta-analyses of voxel-based morphometry (VBM) studies reported lower gray matter volume (GMV) in the amygdala, striatum, insula, precuneus, and frontal and temporal regions in CD youths compared to healthy controls (HCs) (
7- Noordermeer S.D.S.
- Luman M.
- Oosterlaan J.
A systematic review and meta-analysis of neuroimaging in oppositional defiant disorder (ODD) and conduct disorder (CD) taking attention-deficit hyperactivity disorder (ADHD) Into account.
,
8- Rogers J.C.
- De Brito S.A.
Cortical and subcortical gray matter volume in youths with conduct problems: a meta-analysis.
). Overlapping and additional alterations have been reported in surface-based morphometry (SBM) studies. While VBM focuses on GMV as a composite measure, SBM methods assess the components of cortical volume: cortical thickness (CT), surface area (SA) and folding/gyrification. It is important to distinguish between these metrics as they have distinct etiologies and developmental trajectories (
9- Lyall A.E.
- Shi F.
- Geng X.
- Woolson S.
- Li G.
- Wang L.
- et al.
Dynamic development of regional cortical thickness and surface area in early childhood.
,
10- Panizzon M.S.
- Fennema-Notestine C.
- Eyler L.T.
- Jernigan T.L.
- Prom-Wormley E.
- Neale M.
- et al.
Distinct genetic influences on cortical surface area and cortical thickness.
,
11- Raznahan A.
- Shaw P.
- Lalonde F.
- Stockman M.
- Wallace G.L.
- Greenstein D.
- et al.
How does your cortex grow?.
). Amongst the more consistent SBM findings in CD are lower CT in frontal, temporal and parietal regions including the ventromedial prefrontal and orbitofrontal cortex (OFC) (
12- Fairchild G.
- Toschi N.
- Hagan C.C.
- Goodyer I.M.
- Calder A.J.
- Passamonti L.
Cortical thickness, surface area, and folding alterations in male youths with conduct disorder and varying levels of callous–unemotional traits.
,
13- Hyatt C.J.
- Haney-Caron E.
- Stevens M.C.
Cortical thickness and folding deficits in conduct-disordered adolescents.
,
14- Jiang Y.
- Guo X.
- Zhang J.
- Gao J.
- Wang X.
- Situ W.
- et al.
Abnormalities of cortical structures in adolescent-onset conduct disorder.
,
15- Jiang Y.
- Ming Q.
- Gao Y.
- Dong D.
- Sun X.
- Zhang X.
- et al.
Effects of BDNF Val66Met polymorphisms on brain structures and behaviors in adolescents with conduct disorder.
,
16- Smaragdi A.
- Cornwell H.
- Toschi N.
- Riccelli R.
- Gonzalez-Madruga K.
- Wells A.
- et al.
Sex differences in the relationship between conduct disorder and cortical structure in adolescents.
), superior temporal gyrus (STG) (
12- Fairchild G.
- Toschi N.
- Hagan C.C.
- Goodyer I.M.
- Calder A.J.
- Passamonti L.
Cortical thickness, surface area, and folding alterations in male youths with conduct disorder and varying levels of callous–unemotional traits.
,
13- Hyatt C.J.
- Haney-Caron E.
- Stevens M.C.
Cortical thickness and folding deficits in conduct-disordered adolescents.
,
14- Jiang Y.
- Guo X.
- Zhang J.
- Gao J.
- Wang X.
- Situ W.
- et al.
Abnormalities of cortical structures in adolescent-onset conduct disorder.
,
17- Wallace G.L.
- White S.F.
- Robustelli B.
- Sinclair S.
- Hwang S.
- Martin A.
- Blair R.J.R.
Cortical and subcortical abnormalities in youths with conduct disorder and elevated callous-unemotional traits.
) and precuneus (
13- Hyatt C.J.
- Haney-Caron E.
- Stevens M.C.
Cortical thickness and folding deficits in conduct-disordered adolescents.
,
14- Jiang Y.
- Guo X.
- Zhang J.
- Gao J.
- Wang X.
- Situ W.
- et al.
Abnormalities of cortical structures in adolescent-onset conduct disorder.
). While findings for SA and gyrification are more varied, frontal alterations in these metrics have also been reported in CD (
12- Fairchild G.
- Toschi N.
- Hagan C.C.
- Goodyer I.M.
- Calder A.J.
- Passamonti L.
Cortical thickness, surface area, and folding alterations in male youths with conduct disorder and varying levels of callous–unemotional traits.
,
13- Hyatt C.J.
- Haney-Caron E.
- Stevens M.C.
Cortical thickness and folding deficits in conduct-disordered adolescents.
,
14- Jiang Y.
- Guo X.
- Zhang J.
- Gao J.
- Wang X.
- Situ W.
- et al.
Abnormalities of cortical structures in adolescent-onset conduct disorder.
,
16- Smaragdi A.
- Cornwell H.
- Toschi N.
- Riccelli R.
- Gonzalez-Madruga K.
- Wells A.
- et al.
Sex differences in the relationship between conduct disorder and cortical structure in adolescents.
,
17- Wallace G.L.
- White S.F.
- Robustelli B.
- Sinclair S.
- Hwang S.
- Martin A.
- Blair R.J.R.
Cortical and subcortical abnormalities in youths with conduct disorder and elevated callous-unemotional traits.
,
18- Sarkar S.
- Daly E.
- Feng Y.
- Ecker C.
- Craig M.C.
- Harding D.
- et al.
Reduced cortical surface area in adolescents with conduct disorder.
).
However, the heterogeneity in findings limits their contribution to our understanding of CD’s pathophysiology. Beyond methodological issues such as small sample sizes (
19- Button K.S.
- Ioannidis J.P.A.
- Mokrysz C.
- Nosek B.A.
- Flint J.
- Robinson E.S.J.
- Munafò M.R.
Power failure: why small sample size undermines the reliability of neuroscience.
), heterogeneity within the CD phenotype likely contributes to these mixed findings (
6- Fairchild G.
- Hawes D.J.
- Frick P.J.
- Copeland W.E.
- Odgers C.L.
- Franke B.
- et al.
Conduct disorder.
). In addition to factors such as age-of-onset, callous-unemotional traits and sex (
8- Rogers J.C.
- De Brito S.A.
Cortical and subcortical gray matter volume in youths with conduct problems: a meta-analysis.
,
16- Smaragdi A.
- Cornwell H.
- Toschi N.
- Riccelli R.
- Gonzalez-Madruga K.
- Wells A.
- et al.
Sex differences in the relationship between conduct disorder and cortical structure in adolescents.
,
20- Jiang Y.
- Gao Y.
- Dong D.
- Sun X.
- Situ W.
- Yao S.
Structural abnormalities in adolescents with conduct disorder and high versus low callous unemotional traits.
), childhood maltreatment might constitute a further source of heterogeneity in CD. Childhood maltreatment comprises emotional, physical, and sexual abuse, and neglect (
21A developmental psychopathology perspective on child maltreatment.
), and is an important risk factor for various disorders including CD (
22- Bernhard A.
- Martinelli A.
- Ackermann K.
- Saure D.
- Freitag C.M.
Association of trauma, Posttraumatic Stress Disorder and Conduct Disorder: A systematic review and meta-analysis.
,
23- Braga T.
- Gonçalves L.C.
- Basto-Pereira M.
- Maia Â.
Unraveling the link between maltreatment and juvenile antisocial behavior: A meta-analysis of prospective longitudinal studies.
). Multiple (non-exclusive) explanations exist for how maltreatment increases risk for CD. These include social learning processes (
24- Dodge K.A.
- Bates J.E.
- Pettit G.S.
Mechanisms in the cycle of violence.
) and gene-environment correlations (
25- Jaffee S.R.
- Caspi A.
- Moffitt T.E.
- Taylor A.
Physical maltreatment victim to antisocial child: evidence of an environmentally mediated process.
,
26- Schulz-Heik R.J.
- Rhee S.H.
- Silvern L.E.
- Haberstick B.C.
- Hopfer C.
- Lessem J.M.
- Hewitt J.K.
The association between conduct problems and maltreatment: testing genetic and environmental mediation.
). However, a more direct pathway has also been proposed, whereby experiences of severe stressors in childhood become ‘biologically embedded’, thereby conferring latent vulnerability for subsequent psychopathology (
27The theory of latent vulnerability: Reconceptualizing the link between childhood maltreatment and psychiatric disorder.
).
Correspondingly, primary and meta-analytical studies have reported associations between maltreatment and cortical structure in children, adolescents, and adults (
28Neuroimaging of child abuse: a critical review.
,
29Gray matter abnormalities in childhood maltreatment: a voxel-wise meta-analysis.
,
30- Paquola C.
- Bennett M.R.
- Lagopoulos J.
Understanding heterogeneity in grey matter research of adults with childhood maltreatment—A meta-analysis and review.
,
31- Pollok T.M.
- Kaiser A.
- Kraaijenvanger E.J.
- Monninger M.
- Brandeis D.
- Banaschewski T.
- et al.
Neurostructural traces of early life adversities: A meta-analysis exploring age- and adversity-specific effects.
,
32Annual Research Review: Enduring neurobiological effects of childhood abuse and neglect.
). Critically, many of these alterations overlap with those observed in CD, including lower GMV and/or CT in frontal, temporal and parietal regions such as OFC and precuneus (
29Gray matter abnormalities in childhood maltreatment: a voxel-wise meta-analysis.
,
31- Pollok T.M.
- Kaiser A.
- Kraaijenvanger E.J.
- Monninger M.
- Brandeis D.
- Banaschewski T.
- et al.
Neurostructural traces of early life adversities: A meta-analysis exploring age- and adversity-specific effects.
,
33- Kelly P.A.
- Viding E.
- Puetz V.B.
- Palmer A.L.
- Mechelli A.
- Pingault J.-B.
- et al.
Sex differences in socioemotional functioning, attentional bias, and gray matter volume in maltreated children: A multilevel investigation.
,
34- Kelly P.A.
- Viding E.
- Puetz V.B.
- Palmer A.L.
- Samuel S.
- McCrory E.J.
The sexually dimorphic impact of maltreatment on cortical thickness, surface area and gyrification.
,
35- Price M.
- Albaugh M.
- Hahn S.
- Juliano A.C.
- Fani N.
- Brier Z.M.F.
- et al.
Examination of the association between exposure to childhood maltreatment and brain structure in young adults: a machine learning analysis.
,
36- Begemann M.J.H.
- Schutte M.J.L.
- Dellen E van
- Abramovic L.
- Boks M.P.
- Haren NEM van
- et al.
Childhood trauma is associated with reduced frontal gray matter volume: a large transdiagnostic structural MRI study.
). As maltreatment is prevalent in CD youth (
37- Afifi T.O.
- McMillan K.A.
- Asmundson G.J.G.
- Pietrzak R.H.
- Sareen J.
An examination of the relation between conduct disorder, childhood and adulthood traumatic events, and posttraumatic stress disorder in a nationally representative sample.
), this suggests that it may contribute to structural alterations observed in this population. Accordingly, studies into other disorders frequently associated with maltreatment (e.g., depression (
38- Opel N.
- Redlich R.
- Zwanzger P.
- Grotegerd D.
- Arolt V.
- Heindel W.
- et al.
Hippocampal atrophy in major depression: a function of childhood maltreatment rather than diagnosis?.
)) found that at least some of the disorder-related neuroanatomical alterations were specific to patients with maltreatment histories. Based on this and clinical differences between maltreated and non-maltreated patients, Teicher and Samson (
39Childhood maltreatment and psychopathology: a case for ecophenotypic variants as clinically and neurobiologically distinct subtypes.
) proposed that maltreatment-related psychopathology might represent a distinct ‘ecophenotype’ of the same disorder.
As maltreatment is a major risk factor for CD and maltreated and CD youths show overlapping structural alterations, testing the applicability of the ‘ecophenotype’ model to CD is important. Clarifying whether CD youths with versus without maltreatment show distinct alterations from controls and differ from each other may help us understand previous inconsistent findings and would strengthen the case for considering maltreatment in future research. Although much remains to be learned regarding
how maltreatment increases risk for psychopathology, evidence suggests that the relationship might be mediated by maltreatment-related neurobiological adaptations (
27The theory of latent vulnerability: Reconceptualizing the link between childhood maltreatment and psychiatric disorder.
,
40- Bremner J.D.
- Vermetten E.
Stress and development: Behavioral and biological consequences.
). If CD youths with and without maltreatment history differ in brain structure, this might indicate that maltreatment exposure constitutes a distinct pathway to antisocial behavior (
41- van Goozen S.H.M.
- Fairchild G.
- Snoek H.
- Harold G.T.
The evidence for a neurobiological model of childhood antisocial behavior.
) and designates a subgroup of CD youths with distinct neurobiology with implications for theory, assessment, and research.
Despite this, our knowledge of the impact of maltreatment on brain alterations in CD remains limited. In a sample of young women with a history of CD, most group differences in CT and SA (
42- Budhiraja M.
- Pereira J.B.
- Lindner P.
- Westman E.
- Jokinen J.
- Savic I.
- et al.
Cortical structure abnormalities in females with conduct disorder prior to age 15.
) but not GMV (
43- Budhiraja M.
- Savic I.
- Lindner P.
- Jokinen J.
- Tiihonen J.
- Hodgins S.
Brain structure abnormalities in young women who presented conduct disorder in childhood/adolescence.
) remained significant when controlling for abuse. In the first study to explicitly compare CD individuals with and without maltreatment history, Gao and colleagues (
44- Gao Y.
- Jiang Y.
- Ming Q.
- Zhang J.
- Ma R.
- Wu Q.
- et al.
Neuroanatomical changes associated with conduct disorder in boys: influence of childhood maltreatment.
) demonstrated that in addition to main effects of diagnosis on STG (CD<HC) and dorsomedial prefrontal cortex (PFC) volume (CD>HC), CD boys
with maltreatment showed lower dorsolateral PFC volume, but increased posterior cingulate and putamen volume relative to CD boys
without maltreatment. These findings suggest the ‘ecophenotype’ model may be applicable to CD. However, as this study was the first of its kind and recruited a male-only sample, it requires replication and extension to test the robustness and generalizability of findings.
Therefore, we aimed to extend previous research by investigating the structural correlates of CD with versus without maltreatment in a large mixed-sex European sample. Using SBM, we compared controls and CD youths regardless of maltreatment history in terms of cortical structure (assessing cortical volume, CT, SA, and gyrification). We then subdivided the CD group into those with and without maltreatment history and compared each subgroup to controls and each other.
We expected to observe main effects of CD diagnosis in frontal, temporal, and parietal regions, including lower CT in the OFC/ventromedial PFC, STG and precuneus (CD-all<HC). Based on overlapping alterations in CD and maltreated samples, we predicted that some case-control alterations would be specific to the maltreated CD subgroup (e.g., OFC, STG, precuneus (
29Gray matter abnormalities in childhood maltreatment: a voxel-wise meta-analysis.
)) and that differences in overlapping regions would be observed between maltreated and non-maltreated CD youths. Gao and colleagues’ (
44- Gao Y.
- Jiang Y.
- Ming Q.
- Zhang J.
- Ma R.
- Wu Q.
- et al.
Neuroanatomical changes associated with conduct disorder in boys: influence of childhood maltreatment.
) study was published after these predictions were formulated but provided evidence for differences between the CD subgroups in the dorsolateral PFC and posterior cingulate.
DISCUSSION
Using a large mixed-sex sample, this study aimed to investigate cortical structure alterations in CD youths with and without maltreatment and test the ‘ecophenotype’ hypothesis that maltreatment-related CD (CD/+) may be distinct from CD without maltreatment (CD/-) (
39Childhood maltreatment and psychopathology: a case for ecophenotypic variants as clinically and neurobiologically distinct subtypes.
).
In line with our hypotheses and the ‘ecophenotype’ model, maltreated and non-maltreated CD youths demonstrated distinct alterations relative to HCs. Overall, the CD/+ group demonstrated more extensive differences compared with the control group, across multiple measures of cortical structure, including lower CT, volume and gyrification in inferior and middle frontal regions and pre- and postcentral gyri. Conversely, differences between CD/- and HC groups were limited to greater left STG folding. The CD subgroups also differed from each other, with CD/+ youths showing lower right STG volume, right precentral SA and gyrification in frontal, temporal, and parietal regions relative to their CD/- counterparts.
The regions identified when comparing the CD subgroups and controls were largely consistent with previous research. For example, OFC alterations as observed in the CD/+ group were reported in previous studies of CD youths (
12- Fairchild G.
- Toschi N.
- Hagan C.C.
- Goodyer I.M.
- Calder A.J.
- Passamonti L.
Cortical thickness, surface area, and folding alterations in male youths with conduct disorder and varying levels of callous–unemotional traits.
,
14- Jiang Y.
- Guo X.
- Zhang J.
- Gao J.
- Wang X.
- Situ W.
- et al.
Abnormalities of cortical structures in adolescent-onset conduct disorder.
,
16- Smaragdi A.
- Cornwell H.
- Toschi N.
- Riccelli R.
- Gonzalez-Madruga K.
- Wells A.
- et al.
Sex differences in the relationship between conduct disorder and cortical structure in adolescents.
) and maltreated samples (
29Gray matter abnormalities in childhood maltreatment: a voxel-wise meta-analysis.
). The OFC is implicated in emotion regulation, decision-making, and reward/punishment processing (
). Alterations in this region have thus been suggested to underlie neurocognitive impairments in these domains in CD youths (
62- Kohls G.
- Baumann S.
- Gundlach M.
- Scharke W.
- Bernhard A.
- Martinelli A.
- et al.
Investigating sex differences in emotion recognition, learning, and regulation among youths with conduct disorder.
,
63- Fairchild G.
- van Goozen S.H.M.
- Stollery S.J.
- Aitken M.R.F.
- Savage J.
- Moore S.C.
- Goodyer I.M.
Decision making and executive function in male adolescents with early-onset or adolescence-onset conduct disorder and control subjects.
) and emotion dysregulation in maltreated individuals (
64- Weissman D.G.
- Bitran D.
- Miller A.B.
- Schaefer J.D.
- Sheridan M.A.
- McLaughlin K.A.
Difficulties with emotion regulation as a transdiagnostic mechanism linking child maltreatment with the emergence of psychopathology.
). Our findings suggest that OFC alterations may be specific to maltreated CD youths. Likewise, the only difference observed between the CD-all and control groups, lower IFG CT, was only detected in the CD/+ but not the CD/- subgroup. Correspondingly, while alterations in IFG structure have only been reported in a few studies of CD youths and adults with antisocial personality disorder (
13- Hyatt C.J.
- Haney-Caron E.
- Stevens M.C.
Cortical thickness and folding deficits in conduct-disordered adolescents.
,
16- Smaragdi A.
- Cornwell H.
- Toschi N.
- Riccelli R.
- Gonzalez-Madruga K.
- Wells A.
- et al.
Sex differences in the relationship between conduct disorder and cortical structure in adolescents.
,
65- Jiang W.
- Li G.
- Liu H.
- Shi F.
- Wang T.
- Shen C.
- et al.
Reduced cortical thickness and increased surface area in antisocial personality disorder.
), two meta-analyses demonstrated associations between adversity and lower IFG volume (
29Gray matter abnormalities in childhood maltreatment: a voxel-wise meta-analysis.
,
31- Pollok T.M.
- Kaiser A.
- Kraaijenvanger E.J.
- Monninger M.
- Brandeis D.
- Banaschewski T.
- et al.
Neurostructural traces of early life adversities: A meta-analysis exploring age- and adversity-specific effects.
), albeit in the opposite (i.e., left) hemisphere. Together with the current findings, this may suggest that structural alterations in the IFG are specific to CD youths with maltreatment history. These alterations may underlie some of the cognitive and social deficits observed in CD youth, such as reduced inhibitory control (
66- Swick D.
- Ashley V.
- Turken A.U.
Left inferior frontal gyrus is critical for response inhibition.
,
67- Garavan H.
- Ross T.J.
- Stein E.A.
Right hemispheric dominance of inhibitory control: An event-related functional MRI study.
), emotion regulation (
68- Pozzi E.
- Vijayakumar N.
- Rakesh D.
- Whittle S.
Neural correlates of emotion regulation in adolescents and emerging adults: a meta-analytic study.
) and (affective) empathy (
69- Liakakis G.
- Nickel J.
- Seitz R.J.
Diversity of the inferior frontal gyrus—A meta-analysis of neuroimaging studies.
,
70- Shamay-Tsoory S.G.
- Aharon-Peretz J.
- Perry D.
Two systems for empathy: a double dissociation between emotional and cognitive empathy in inferior frontal gyrus versus ventromedial prefrontal lesions.
).
Conversely, greater left STG folding was only observed in the CD/- subgroup. STG alterations have frequently been reported in CD youths. Whilst most studies demonstrated decreased STG CT (
12- Fairchild G.
- Toschi N.
- Hagan C.C.
- Goodyer I.M.
- Calder A.J.
- Passamonti L.
Cortical thickness, surface area, and folding alterations in male youths with conduct disorder and varying levels of callous–unemotional traits.
,
14- Jiang Y.
- Guo X.
- Zhang J.
- Gao J.
- Wang X.
- Situ W.
- et al.
Abnormalities of cortical structures in adolescent-onset conduct disorder.
), higher gyrification and SA have been reported in a partly overlapping sample (
16- Smaragdi A.
- Cornwell H.
- Toschi N.
- Riccelli R.
- Gonzalez-Madruga K.
- Wells A.
- et al.
Sex differences in the relationship between conduct disorder and cortical structure in adolescents.
) and women with past CD diagnoses even when adjusting for prior abuse (
42- Budhiraja M.
- Pereira J.B.
- Lindner P.
- Westman E.
- Jokinen J.
- Savic I.
- et al.
Cortical structure abnormalities in females with conduct disorder prior to age 15.
). As the STG is involved in a host of (social) cognitive processes [e.g., speech processing, (emotional) face processing (
71Superior temporal sulcus—it’s my area: or is it?.
)], STG alterations may underlie CD-associated deficits in facial and vocal emotion recognition (
62- Kohls G.
- Baumann S.
- Gundlach M.
- Scharke W.
- Bernhard A.
- Martinelli A.
- et al.
Investigating sex differences in emotion recognition, learning, and regulation among youths with conduct disorder.
). Our findings suggest that greater
left STG folding may be specific to non-maltreated CD youths. However, the CD/+ subgroup demonstrated lower
right STG volume compared to CD/- (but not HC) youths, consistent with reports of STG alterations in maltreated samples (
29Gray matter abnormalities in childhood maltreatment: a voxel-wise meta-analysis.
). This suggests that STG structure might also be influenced by maltreatment but that the measure, direction and/or laterality of effects might differ between maltreated and CD groups.
Further differences between the CD subgroups included lower rostral middle frontal, supramarginal, fusiform and inferior temporal gyrification in the CD/+ group. Although few maltreatment studies have investigated folding, alterations in overlapping regions have been reported, such as lower supramarginal gyrus volume in psychopathology-free children with documented maltreatment exposure (
33- Kelly P.A.
- Viding E.
- Puetz V.B.
- Palmer A.L.
- Mechelli A.
- Pingault J.-B.
- et al.
Sex differences in socioemotional functioning, attentional bias, and gray matter volume in maltreated children: A multilevel investigation.
) and lower fusiform gyrus volume in women who experienced childhood sexual abuse (
72- Tomoda A.
- Navalta C.P.
- Polcari A.
- Sadato N.
- Teicher M.H.
Childhood sexual abuse is associated with reduced gray matter volume in visual cortex of young women.
). Critically, while our findings demonstrate extensive neurobiological differences between CD/+ and CD/- youths, only one region was also identified when comparing each of the subgroups with controls: CD/+ youths showed lower rostral MFG folding compared to both the CD/- and HC groups. This provides strong evidence that lower rostral MFG gyrification is specific to the CD/+ group. This region is implicated in cognitive flexibility, response selection, working memory and decision-making (
73- Seminowicz D.A.
- Moayedi M.
The dorsolateral prefrontal cortex in acute and chronic pain.
), with meta-analytical evidence supporting maltreatment-related differences in this region (
28Neuroimaging of child abuse: a critical review.
,
30- Paquola C.
- Bennett M.R.
- Lagopoulos J.
Understanding heterogeneity in grey matter research of adults with childhood maltreatment—A meta-analysis and review.
). Correspondingly, the only other study that investigated the influence of maltreatment on brain structure in CD (
44- Gao Y.
- Jiang Y.
- Ming Q.
- Zhang J.
- Ma R.
- Wu Q.
- et al.
Neuroanatomical changes associated with conduct disorder in boys: influence of childhood maltreatment.
) identified lower right rostral/caudal MFG volume in CD/+ relative to CD/- youth. Overlap between the two studies’ findings was otherwise limited, potentially owing to differences in assessment of maltreatment and sample characteristics (males-only versus a mixed-sex sample).
We note that adjusting for IQ, SES, and particularly attention problems affected our findings (e.g., in the CD/+ versus HC comparisons, only volumetric differences in the postcentral gyrus and rostral MFG survived correction for attention problems). Attenuation of brain differences when controlling for ADHD(-like) symptoms and/or IQ is common in the CD literature (
12- Fairchild G.
- Toschi N.
- Hagan C.C.
- Goodyer I.M.
- Calder A.J.
- Passamonti L.
Cortical thickness, surface area, and folding alterations in male youths with conduct disorder and varying levels of callous–unemotional traits.
,
16- Smaragdi A.
- Cornwell H.
- Toschi N.
- Riccelli R.
- Gonzalez-Madruga K.
- Wells A.
- et al.
Sex differences in the relationship between conduct disorder and cortical structure in adolescents.
). While it is important to assess which effects are CD-specific, as ADHD and CD are highly comorbid (
59- Angold A.
- Costello E.J.
- Erkanli A.
Comorbidity.
), uncorrected findings might be more representative of clinical reality (
12- Fairchild G.
- Toschi N.
- Hagan C.C.
- Goodyer I.M.
- Calder A.J.
- Passamonti L.
Cortical thickness, surface area, and folding alterations in male youths with conduct disorder and varying levels of callous–unemotional traits.
) and adjusting for ADHD may also remove CD-related effects. Similarly, increased rates of ADHD have been reported in individuals who experienced early deprivation (
74- Kennedy M.
- Kreppner J.
- Knights N.
- Kumsta R.
- Maughan B.
- Golm D.
- et al.
Early severe institutional deprivation is associated with a persistent variant of adult attention-deficit/hyperactivity disorder: clinical presentation, developmental continuities and life circumstances in the English and Romanian Adoptees study.
). This suggests that maltreatment may constitute one causal pathway to attention problems and that adjusting for the latter could also remove maltreatment-related effects.
Overall, our results indicate that maltreated CD youths showed more extensive alterations in multiple measures of cortical structure than non-maltreated CD youths, despite having similar clinical and demographic profiles. Differences in the CD/+ subgroup might be partly explained by the effects of maltreatment on neurobiological systems, most prominently the hypothalamic-pituitary-adrenal axis (
75- Bunea I.M.
- Szentágotai-Tătar A.
- Miu A.C.
Early-life adversity and cortisol response to social stress: a meta-analysis.
,
76- Lupien S.J.
- McEwen B.S.
- Gunnar M.R.
- Heim C.
Effects of stress throughout the lifespan on the brain, behaviour and cognition.
). Adaptations in the body’s (neuro)hormonal stress system could affect neurodevelopmental processes including neurogenesis, synaptic pruning and myelination, with downstream effects on brain structure and function (
32Annual Research Review: Enduring neurobiological effects of childhood abuse and neglect.
,
77Stress signalling pathways that impair prefrontal cortex structure and function.
). Importantly, maltreatment-induced alterations may initially reflect adaptive changes, which later become maladaptive in a normative environment, increasing vulnerability to psychopathology (
27The theory of latent vulnerability: Reconceptualizing the link between childhood maltreatment and psychiatric disorder.
,
32Annual Research Review: Enduring neurobiological effects of childhood abuse and neglect.
).
As gyrification peaks in infancy and volume, CT, and SA peak in late childhood/early adolescence with subsequent declines (
11- Raznahan A.
- Shaw P.
- Lalonde F.
- Stockman M.
- Wallace G.L.
- Greenstein D.
- et al.
How does your cortex grow?.
), our findings of maltreatment-related regional decreases in the CD/+ subgroup (relative to the other groups) may reflect accelerated cortical development. This fits with the stress acceleration model of maltreatment, which postulates that stress-induced neurobiological changes result in accelerated brain maturation, especially in regions involved in emotion processing (e.g., OFC (
78- Callaghan B.L.
- Tottenham N.
The Stress Acceleration Hypothesis: effects of early-life adversity on emotion circuits and behavior.
)). In line with this and our observation of lower rostral MFG gyrification in the CD/+ group, a recent study found advanced rostral MFG maturation in abused girls, albeit only in those without psychopathology (
79- Keding T.J.
- Heyn S.A.
- Russell J.D.
- Zhu X.
- Cisler J.
- McLaughlin K.A.
- Herringa R.J.
Differential patterns of delayed emotion circuit maturation in abused girls with and without internalizing psychopathology.
). Interestingly, while the CD/+ subgroup differed from controls and CD/- youths on multiple cortical structure metrics, most differences between the CD subgroups were found for gyrification. This is surprising as evidence suggests that sulcal and gyral patterns develop mostly in utero and are under strong genetic influence (
80- White T.
- Su S.
- Schmidt M.
- Kao C.-Y.
- Sapiro G.
The development of gyrification in childhood and adolescence.
,
81- Schmitt J.E.
- Raznahan A.
- Liu S.
- Neale M.C.
The heritability of cortical folding: evidence from the Human Connectome Project.
). Further research is needed to understand the (potential) impact of adversity on gyrification.
Our findings have important implications for theory, research, and practice. First, corresponding to the ‘ecophenotype’ model (
39Childhood maltreatment and psychopathology: a case for ecophenotypic variants as clinically and neurobiologically distinct subtypes.
), they suggest that despite having the same diagnosis, CD youths with and without maltreatment differ from each other and show different alterations compared to controls (
39Childhood maltreatment and psychopathology: a case for ecophenotypic variants as clinically and neurobiologically distinct subtypes.
). This supports the hypothesis that maltreatment, a major risk factor for CD (
22- Bernhard A.
- Martinelli A.
- Ackermann K.
- Saure D.
- Freitag C.M.
Association of trauma, Posttraumatic Stress Disorder and Conduct Disorder: A systematic review and meta-analysis.
,
37- Afifi T.O.
- McMillan K.A.
- Asmundson G.J.G.
- Pietrzak R.H.
- Sareen J.
An examination of the relation between conduct disorder, childhood and adulthood traumatic events, and posttraumatic stress disorder in a nationally representative sample.
), designates a potentially meaningful ‘ecophenotypic’ (i.e., environmentally-mediated) variant of CD, which differs neurobiologically from non-maltreated CD. This highlights the importance of investigating the utility of subtyping CD youths by maltreatment history and suggests that through its effects on neurobiological systems, maltreatment might constitute a distinct developmental pathway to CD (
41- van Goozen S.H.M.
- Fairchild G.
- Snoek H.
- Harold G.T.
The evidence for a neurobiological model of childhood antisocial behavior.
). However, further research is needed to substantiate these claims and rule out alternative explanations. For example, given our cross-sectional design and limited information about maltreatment timing, we cannot rule out whether CD/+ youths would have developed CD regardless of maltreatment exposure and/or whether the CD preceded and increased the child's risk of experiencing maltreatment (
22- Bernhard A.
- Martinelli A.
- Ackermann K.
- Saure D.
- Freitag C.M.
Association of trauma, Posttraumatic Stress Disorder and Conduct Disorder: A systematic review and meta-analysis.
). We also note that many regions that differed when comparing the CD subgroups with controls were not identified when directly contrasting the CD subgroups. Hence, alterations that emerged when contrasting CD/+ youth and controls, but not in the other comparison, could reflect
quantitative differences between the CD subgroups (i.e., one group shows a stronger effect but it is still present in the same location/direction in the other) rather than
qualitative differences (i.e., CD subgroups display alterations in different regions/opposite directions). Further studies including maltreated HCs could help to address these issues by further disentangling maltreatment- and disorder-related effects and establishing specificity through interaction analyses (
82- Nieuwenhuis S.
- Forstmann B.U.
- Wagenmakers E.-J.
Erroneous analyses of interactions in neuroscience: a problem of significance.
). Second, our findings indicate that maltreatment contributes to heterogeneity within CD, at least at a structural level, and may have been an important confound in earlier neuroimaging studies (
32Annual Research Review: Enduring neurobiological effects of childhood abuse and neglect.
). When considering the overall CD group in the current sample (‘enriched’ for maltreatment), we were unable to replicate many of the alterations previously reported in CD (e.g., lower OFC/ventromedial PFC thickness). This highlights the importance of assessing for maltreatment in future studies.
This study had several limitations. First, we used a dichotomous measure of maltreatment, and were unable to explore effects of heterogeneity in maltreatment exposure such as type, timing, or severity (
83- McLaughlin K.A.
- Sheridan M.A.
Beyond cumulative risk: a dimensional approach to childhood adversity.
,
84Rethinking concepts and categories for understanding the neurodevelopmental effects of childhood adversity.
). Relatedly, our maltreatment measure primarily reflected experiences of physical and sexual abuse and did not capture neglect or other adversities which may also impact the brain and psychopathology (
31- Pollok T.M.
- Kaiser A.
- Kraaijenvanger E.J.
- Monninger M.
- Brandeis D.
- Banaschewski T.
- et al.
Neurostructural traces of early life adversities: A meta-analysis exploring age- and adversity-specific effects.
,
85Examining the common and specific grey matter abnormalities in childhood maltreatment and peer victimisation.
). Second, we relied on retrospective reports from parents or caregivers who may be unaware that their child has been maltreated or purposefully untruthful. However, the CBE interview aims to increase honesty by focusing on whether maltreatment occurred, rather than the perpetrator’s identity (
24- Dodge K.A.
- Bates J.E.
- Pettit G.S.
Mechanisms in the cycle of violence.
,
86- Arseneault L.
- Cannon M.
- Fisher H.L.
- Polanczyk G.
- Moffitt T.E.
- Caspi A.
Childhood trauma and children’s emerging psychotic symptoms: a genetically sensitive longitudinal cohort study.
). Third, collapsing across sex and a wide age range could have impacted our findings. However, we controlled for both factors in our analyses and re-ran the analyses in a male-only subsample. Lastly, while our sample size was larger than most previous neuroimaging studies of CD, recent evidence (
87- Marek S.
- Tervo-Clemmens B.
- Calabro F.J.
- Montez D.F.
- Kay B.P.
- Hatoum A.S.
- et al.
Reproducible brain-wide association studies require thousands of individuals.
) suggests that our analyses might not have been adequately powered to detect small effects, highlighting the need for replications in larger samples (see Supplement for further discussion of this issue).
In summary, using a large, mixed-sex sample and sensitive SBM methods to assess multiple cortical properties based on carefully quality controlled and edited data, we found that maltreated and non-maltreated CD subgroups showed distinct neurobiological differences compared to age-matched controls and also differed from each other. Despite similar clinical profiles, maltreated CD youths showed more widespread structural alterations relative to controls, and lower volume, SA and gyrification in frontal, temporal, and parietal regions than non-maltreated CD youths. This supports the ‘ecophenotype’ model, indicating that higher rates of maltreatment in CD youth likely contributed to some of the structural alterations reported in this population and that maltreatment-related and non-maltreatment-related forms of CD might be partly distinct neurobiologically. Findings highlight the need to consider maltreatment in future studies of CD (and other psychiatric disorders) and provide a platform for further research investigating the impact of maltreatment type, timing, and severity/chronicity, and differences in brain activation and neurocognitive functioning between maltreated and non-maltreated CD youths.
Article info
Publication history
Accepted:
December 19,
2022
Received in revised form:
November 16,
2022
Received:
October 3,
2022
Publication stage
In Press Journal Pre-ProofFootnotes
ACKNOWLEDGMENTS AND DISCLOSURES
This study was supported in part by grant ES/P000630/1 for the SWDTP awarded to the Universities of Bath, Bristol, Exeter, Plymouth and West of England (UWE) from the Economic and Social Research Council (ESRC)/UKRI and grant MR/N0137941/1 for the GW4 BIOMED MRC DTP awarded to the Universities of Bath, Bristol, Cardiff and Exeter from the Medical Research Council (MRC)/UKRI.
The FemNAT-CD study was funded by the European Commission’s Seventh Framework Programme (FP7/2007-2013, grant number 602407, coordinator Christine M. Freitag).
We thank Sarah Koerner for her help pre-processing the data and the young people and their families for taking part in the FemNAT-CD study.
Christina Stadler receives royalties for a book on aggression. Christine M. Freitag receives royalties for books on Attention-Deficit/Hyperactivity Disorder, Autism Spectrum Disorder, and Depression. Stephane A. De Brito has received speaker fees from the Child Mental Health Centre and the Centre for Integrated Molecular Brain Imaging. All other authors report no biomedical financial interests or potential conflicts of interest.
Preliminary results from this study were presented as a poster at the Annual Meetings of the Society of Biological Psychiatry, April 29 – May 01, 2021, and the Organization for Human Brain Mapping, June 21 – June 25, 2021.
Copyright
© 2022 Published by Elsevier Inc on behalf of Society of Biological Psychiatry.