Conduct disorder in adolescent females: current state of research and study design of the FemNAT-CD consortium

Moving forward. Use of the START NOW skills training program for female youth with ODD and CD - a commentary on Stadler et al. (2024)

Female youth with oppositional defiant disorder (ODD) and conduct disorder (CD) are an under studied and underserved population at high risk for poor adjustment in later life. Stadler et al. (2024) attempt to redress this situation for adolescent females with CD or ODD with an adapted version of the skills training program START NOW. They describe the results of an ambitious randomized control trial, comparing START NOW with standard care in youth welfare settings in Germany, Switzerland, and The Netherlands. The findings appear promising, but the paper is especially valuable for the spotlight it shines on the needs of this underserved population and those caring for them, together with the importance of undertaking such trials despite their challenges. This commentary seeks to encourage readers to engage with the START NOW trial.

Does the Relationship between Age and Brain Structure Differ in Youth with Conduct Disorder?

Conduct disorder (CD) is characterised by persistent antisocial and aggressive behaviour and typically emerges in childhood or adolescence. Although several authors have proposed that CD is a neurodevelopmental disorder, very little evidence is available about brain development in this condition. Structural brain alterations have been observed in CD, and some indirect evidence for delayed brain maturation has been reported. However, no detailed analysis of age-related changes in brain structure in youth with CD has been conducted. Using cross-sectional MRI data, this study aimed to explore differences in brain maturation in youth with CD versus healthy controls to provide further understanding of the neurodevelopmental processes underlying CD. 291 CD cases (153 males) and 379 healthy controls (160 males) aged 9-18 years (Mage = 14.4) were selected from the European multisite FemNAT-CD study. Structural MRI scans were analysed using surface-based morphometry followed by application of the ENIGMA quality control protocols. An atlas-based approach was used to investigate group differences and test for group-by-age and group-by-age-by-sex interactions in cortical thickness, surface area and subcortical volumes. Relative to healthy controls, the CD group showed lower surface area across frontal, temporal and parietal regions as well as lower total surface area. No significant group-by-age or group-by-age-by-sex interactions were observed on any brain structure measure. These findings suggest that CD is associated with lower surface area across multiple cortical regions, but do not support the idea that CD is associated with delayed brain maturation, at least within the age bracket considered here.

Social isolation and aggression training lead to escalated aggression and hypothalamus-pituitary-gonad axis hyperfunction in mice

Although the participation of sex hormones and sex hormone-responsive neurons in aggressive behavior has been extensively studied, the role of other systems within the hypothalamus-pituitary-gonadal (HPG) axis remains elusive. Here we assessed how the gonadotropin-releasing hormone (GnRH) and kisspeptin systems are impacted by escalated aggression in male mice. We used a combination of social isolation and aggression training (IST) to exacerbate mice's aggressive behavior. Next, low-aggressive (group-housed, GH) and highly aggressive (IST) mice were compared regarding neuronal activity in the target populations and hormonal levels, using immunohistochemistry and ELISA, respectively. Finally, we used pharmacological and viral approaches to manipulate neuropeptide signaling and expression, subsequently evaluating its effects on behavior. IST mice exhibited enhanced aggressive behavior compared to GH controls, which was accompanied by elevated neuronal activity in GnRH neurons and arcuate nucleus kisspeptin neurons. Remarkably, IST mice presented an increased number of kisspeptin neurons in the anteroventral periventricular nucleus (AVPV). In addition, IST mice exhibited elevated levels of luteinizing hormone (LH) in serum. Accordingly, activation and blockade of GnRH receptors (GnRHR) exacerbated and reduced aggression, respectively. Surprisingly, kisspeptin had intricate effects on aggression, i.e., viral ablation of AVPV-kisspeptin neurons impaired the training-induced rise in aggressive behavior whereas kisspeptin itself strongly reduced aggression in IST mice. Our results indicate that IST enhances aggressive behavior in male mice by exacerbating HPG-axis activity. Particularly, increased GnRH neuron activity and GnRHR signaling were found to underlie aggression whereas the relationship with kisspeptin remains puzzling.

Identifying cortical structure markers of resilience to adversity in young people using surface-based morphometry

Previous research on the neurobiological bases of resilience in youth has largely used categorical definitions of resilience and voxel-based morphometry methods that assess gray matter volume. However, it is important to consider brain structure more broadly as different cortical properties have distinct developmental trajectories. To address these limitations, we used surface-based morphometry and data-driven, continuous resilience scores to examine associations between resilience and cortical structure. Structural MRI data from 286 youths (Mage = 13.6 years, 51% female) who took part in the European multi-site FemNAT-CD study were pre-processed and analyzed using surface-based morphometry. Continuous resilience scores were derived for each participant based on adversity exposure and levels of psychopathology using the residual regression method. Vertex-wise analyses assessed for correlations between resilience scores and cortical thickness, surface area, gyrification and volume. Resilience scores were positively associated with right lateral occipital surface area and right superior frontal gyrification and negatively correlated with left inferior temporal surface area. Moreover, sex-by-resilience interactions were observed for gyrification in frontal and temporal regions. Our findings extend previous research by revealing that resilience is related to surface area and gyrification in frontal, occipital and temporal regions that are implicated in emotion regulation and face or object recognition.

Reduced prosocial motivation and effort in adolescents with conduct problems and callous-unemotional traits

BACKGROUND

Prosocial behaviours - acts that benefit others - are of crucial importance for many species including humans. However, adolescents with conduct problems (CP), unlike their typically developing (TD) peers, demonstrate markedly reduced engagement in prosocial behaviours. This pattern is particularly pronounced in adolescents with CP and high levels of callous-unemotional traits (CP/HCU) who are at increased risk of developing psychopathy in adulthood. While a substantial amount of research has investigated the cognitive-affective mechanisms thought to underlie antisocial behaviour, much less is known about the mechanisms that could explain reduced prosocial behaviours in adolescents with CP.

METHODS

Here we examined the willingness to exert effort to benefit oneself (self) and another person (other, prosocial condition) in children with CP/HCU, CP and lower levels of CU traits (CP/LCU) and their TD peers. The task captured both prosocial choices, and actual effort exerted following prosocial choices, in adolescent boys aged 11-16 (27 CP/HCU; 34 CP/LCU; 33 TD). We used computational modelling to reveal the mechanistic processes involved when choosing prosocial acts.

RESULTS

We found that both CP/HCU and CP/LCU groups were more averse to initiating effortful prosocial acts than TD adolescents - both at a cognitive and at a behavioural level. Strikingly, even if they chose to initiate a prosocial act, the CP/HCU group exerted less effort following this prosocial choice than other groups.

CONCLUSIONS

Our findings indicate that reduced exertion of effort to benefit others may be an important factor that differentiates adolescents with CP/HCU from their peers with CP/LCU. They offer new insights into what might drive low prosocial behaviour in adolescents with CP, including vulnerabilities that may particularly characterise those with high levels of CU traits.

Is there a gender paradox in the association between conduct problems and cannabis use? A cohort-study among Swedish adolescents

INTRODUCTION

Conduct problems (CP) predict cannabis use prospectively but the research is mixed as to whether this association is stronger among girls. A stronger association among girls would suggest a 'gender paradox' as both CP and cannabis use is less common in this group. This study aimed to assess whether the longitudinal association between CP and cannabis use in Swedish adolescents is stronger among girls.

METHODS

Data from two waves of a nationally representative cohort study of Swedish adolescents born in 2001 were used. Baseline measurements were collected in 9th grade (at age 15-16) and follow-up measures at 11th grade (at age 17-18).

RESULTS

CP at baseline were significantly associated with cannabis use at follow-up adjusted for hyperactivity problems, emotional problems, socio-demographics, parental monitoring, school grades and truancy at baseline (odds ratio [OR] 1.14, 95% confidence interval [CI] 1.06-1.24) but not when also adjusting for substance use at baseline. Boys were more likely to have used cannabis during the past year, even when controlling for prior substance use (OR 2.29, 95% CI 1.76-2.98). The association between CP and cannabis use was significantly weaker for boys (OR 0.83, 95% CI 0.72-0.95 in the fully adjusted model). The predicted probability of cannabis use was stable at 0.13 for boys across levels of CP, but ranged from 0.05 to 0.16 for girls.

DISCUSSION AND CONCLUSION

The longitudinal association between CP and cannabis use was stronger among girls. The findings are indicative of a 'gender paradox' in the association between CP and cannabis use.

Emotion processing in maltreated boys and girls: Evidence for latent vulnerability

Evidence of alterations in emotion processing in maltreated youth has been hypothesized to reflect latent vulnerability for psychopathology. However, previous studies have not systematically examined the influence of psychopathology on the results. Here, we examined emotion recognition and learning in youth who differed in terms of presence vs. absence of maltreatment and psychopathology and tested for potential sex effects. Maltreatment and psychopathology were assessed in 828 youth (514 females) aged 9-18 years using diagnostic interviews and self- and parent-report questionnaires. Emotion recognition was assessed via identification of morphed facial expressions of six universal emotions. For emotion learning, reward and punishment values were assigned to novel stimuli and participants had to learn to correctly respond/withhold response to stimuli to maximize points. A three-way interaction of maltreatment by psychopathology by emotion indicated that when psychopathology was low, maltreated youth were less accurate than non-maltreated youth for happy, fear and disgust. A three-way interaction of sex, maltreatment and emotion indicated that maltreated girls and boys were impaired for fear, but girls showed an impairment for happy, while boys for disgust. There were no effects of maltreatment, psychopathology, or sex on reward learning. However, a two-way interaction between sex and maltreatment showed that maltreated girls were worse at learning from punishment relative to non-maltreated girls, while maltreated boys were better than non-maltreated boys. The study provides the first clear evidence of latent-vulnerability in emotion recognition in maltreated youth and suggests that girls and boys might be characterized by distinct profiles of emotion recognition and learning following maltreatment.

Identifying structural brain markers of resilience to adversity in young people using voxel-based morphometry

There is increasing evidence that resilience in youth may have a neurobiological basis. However, the existing literature lacks a consistent way of operationalizing resilience, often relying on arbitrary judgments or narrow definitions (e.g., not developing PTSD) to classify individuals as resilient. Therefore, this study used data-driven, continuous resilience scores based on adversity and psychopathology to investigate associations between resilience and brain structure in youth. Structural MRI data from 298 youth aged 9-18 years (Mage = 13.51; 51% female) who participated in the European multisite FemNAT-CD study were preprocessed using SPM12 and analyzed using voxel-based morphometry. Resilience scores were derived by regressing data on adversity exposure against current/lifetime psychopathology and quantifying each individual's distance from the regression line. General linear models tested for associations between resilience and gray matter volume (GMV) and examined whether associations between resilience and GMV differed by sex. Resilience was positively correlated with GMV in the right inferior frontal and medial frontal gyri. Sex-by-resilience interactions were observed in the middle temporal and middle frontal gyri. These findings demonstrate that resilience in youth is associated with volume in brain regions implicated in executive functioning, emotion regulation, and attention. Our results also provide evidence for sex differences in the neurobiology of resilience.

An appetite for aggressive behavior? Female rats, too, derive reward from winning aggressive interactions

While aggression is an adaptive behavior mostly triggered by competition for resources, it can also in and of itself be rewarding. Based on the common notion that female rats are not aggressive, much of aggression research has been centered around males, leading to a gap in the understanding of the female aggression neurobiology. Therefore, we asked whether intact virgin female rats experience reward from an aggressive interaction and assessed aggression seeking behavior in rats of both sexes. To validate the involvement of reward signaling, we measured mesolimbic dopamine turnover and determined the necessity of dopamine signaling for expression of aggression-seeking. Together our data indicate that female rats exhibit aggressive behavior outside of maternal context, experience winning aggressive behaviors as rewarding, and do so to a similar extent as male rats and in a dopamine-dependent manner.

Action initiation and punishment learning differ from childhood to adolescence while reward learning remains stable

Theoretical and empirical accounts suggest that adolescence is associated with heightened reward learning and impulsivity. Experimental tasks and computational models that can dissociate reward learning from the tendency to initiate actions impulsively (action initiation bias) are thus critical to characterise the mechanisms that drive developmental differences. However, existing work has rarely quantified both learning ability and action initiation, or it has relied on small samples. Here, using computational modelling of a learning task collected from a large sample (N = 742, 9-18 years, 11 countries), we test differences in reward and punishment learning and action initiation from childhood to adolescence. Computational modelling reveals that whilst punishment learning rates increase with age, reward learning remains stable. In parallel, action initiation biases decrease with age. Results are similar when considering pubertal stage instead of chronological age. We conclude that heightened reward responsivity in adolescence can reflect differences in action initiation rather than enhanced reward learning.

Molecular signature of excessive female aggression: study of stressed mice with genetic inactivation of neuronal serotonin synthesis

Aggression is a complex social behavior, critically involving brain serotonin (5-HT) function. The neurobiology of female aggression remains elusive, while the incidence of its manifestations has been increasing. Yet, animal models of female aggression are scarce. We previously proposed a paradigm of female aggression in the context of gene x environment interaction where mice with partial genetic inactivation of tryptophan hydroxylase-2 (Tph2+/- mice), a key enzyme of neuronal 5-HT synthesis, are subjected to predation stress resulting in pathological aggression. Using deep sequencing and the EBSeq method, we studied the transcriptomic signature of excessive aggression in the prefrontal cortex of female Tph2+/- mice subjected to rat exposure stress and food deprivation. Challenged mutants, but not other groups, displayed marked aggressive behaviors. We found 26 genes with altered expression in the opposite direction between stressed groups of both Tph2 genotypes. We identified several molecular markers, including Dgkh, Arfgef3, Kcnh7, Grin2a, Tenm1 and Epha6, implicated in neurodevelopmental deficits and psychiatric conditions featuring impaired cognition and emotional dysregulation. Moreover, while 17 regulons, including several relevant to neural plasticity and function, were significantly altered in stressed mutants, no alteration in regulons was detected in stressed wildtype mice. An interplay of the uncovered pathways likely mediates partial Tph2 inactivation in interaction with severe stress experience, thus resulting in excessive female aggression.

Perpetrators and victims of cyberbullying among youth with conduct disorder

Due to modern technological innovations, aggressive behaviors have expanded into the cyberspace, creating a new matter of public concern: cyberbullying. Antisocial and aggressive behaviors, including bullying are characteristic for children and adolescents diagnosed with conduct disorder (CD), raising the question whether these youths are highly involved in cyberbullying experiences, too. 206 participants with CD versus typically developing controls (TDCs) aged 9-19 years (57% girls) were included in the study. Individuals completed several self-report measures investigating cyber- and traditional bullying experiences, and hierarchical multiple regression analyses were conducted to explain the relationship between cyberbullying victimization and perpetration with demographic and clinical variables. Experiences of cyberbullying victimization and perpetration were significantly higher among youth with CD compared to TDCs, and this was accompanied by significantly higher scores on a measure of traditional bullying in CD versus TDCs. CD diagnosis, female sex and higher levels of callous-unemotional (CU) traits were each uniquely associated with increased experiences of cyberbullying victimization, whereas CD diagnosis, higher levels of CU traits and older age were each uniquely associated with increased experiences of cyberbullying perpetration. Individuals with CD, compared to TDCs are at higher risk of becoming cyberbully victims and perpetrators, hence representing an important novel aspect in the assessment and treatment of these youths.

A neurocognitive model of early onset persistent and desistant antisocial behavior in early adulthood

It remains unclear which functional and neurobiological mechanisms are associated with persistent and desistant antisocial behavior in early adulthood. We reviewed the empirical literature and propose a neurocognitive social information processing model for early onset persistent and desistant antisocial behavior in early adulthood, focusing on how young adults evaluate, act upon, monitor, and learn about their goals and self traits. Based on the reviewed literature, we propose that persistent antisocial behavior is characterized by domain-general impairments in self-relevant and goal-related information processing, regulation, and learning, which is accompanied by altered activity in fronto-limbic brain areas. We propose that desistant antisocial development is associated with more effortful information processing, regulation and learning, that possibly balances self-relevant goals and specific situational characteristics. The proposed framework advances insights by considering individual differences such as psychopathic personality traits, and specific emotional characteristics (e.g., valence of social cues), to further illuminate functional and neural mechanisms underlying heterogenous developmental pathways. Finally, we address important open questions and offer suggestions for future research to improve scientific knowledge on general and context-specific expression and development of antisocial behavior in early adulthood.

Testing the Ecophenotype Model: Cortical Structure Alterations in Conduct Disorder With Versus Without Childhood Maltreatment

BACKGROUND

Childhood maltreatment is common in youths with conduct disorder (CD), and both CD and maltreatment have been linked to neuroanatomical alterations. Nonetheless, our understanding of the contribution of maltreatment to the neuroanatomical alterations observed in CD remains limited. We tested the applicability of the ecophenotype model to CD, which holds that maltreatment-related psychopathology is (neurobiologically) distinct from psychopathology without maltreatment.

METHODS

Surface-based morphometry was used to investigate cortical volume, thickness, surface area, and gyrification in a mixed-sex sample of participants with CD (n = 114) and healthy control subjects (HCs) (n = 146), ages 9 to 18 years. Using vertexwise general linear models adjusted for sex, age, total intracranial volume, and site, the control group was compared with the overall CD group and the CD subgroups with (n = 49) versus without (n = 65) maltreatment (assessed by the Children's Bad Experiences interview). These subgroups were also directly compared.

RESULTS

The overall CD group showed lower cortical thickness in the right inferior frontal gyrus. CD youths with a history of maltreatment showed more widespread structural alterations relative to HCs, comprising lower thickness, volume, and gyrification in inferior and middle frontal regions. Conversely, CD youths with no history of maltreatment only showed greater left superior temporal gyrus folding relative to HCs. When contrasting the CD subgroups, those with maltreatment displayed lower right superior temporal gyrus volume, right precentral gyrus surface area, and gyrification in frontal, temporal, and parietal regions.

CONCLUSIONS

Consistent with the ecophenotype model, findings indicated that CD youths with versus without maltreatment differ neurobiologically. This highlights the importance of considering maltreatment history in neuroimaging studies of CD and other disorders.

Synthetic Oxytocin and Vasopressin Act Within the Central Amygdala to Exacerbate Aggression in Female Wistar Rats

Exacerbated aggression is a high-impact, but poorly understood core symptom of several psychiatric disorders, which can also affect women. Animal models have successfully been employed to unravel the neurobiology of aggression. However, despite increasing evidence for sex-specificity, little is known about aggression in females. Here, we studied the role of the oxytocin (OXT) and arginine vasopressin (AVP) systems within the central amygdala (CeA) on aggressive behavior displayed by virgin female Wistar rats using immunohistochemistry, receptor autoradiography, and neuropharmacology. Our data show that CeA GABAergic neurons are activated after an aggressive encounter in the female intruder test. Additionally, neuronal activity (pERK) negatively correlated with the display of aggression in low-aggressive group-housed females. Binding of OXT receptors, but not AVP-V1a receptors, was increased in the CeA of high-aggressive isolated and trained (IST) females. Finally, local infusion of either synthetic OXT or AVP enhanced aggression in IST females, whereas blockade of either of these receptors did not affect aggressive behavior. Altogether, our data support a moderate role of the CeA in female aggression. Regarding neuropeptide signaling, our findings suggest that synthetic, but not endogenous OXT and AVP modulate aggressive behavior in female Wistar rats.

Editorial: The Importance of Considering Multiple Factors Simultaneously to Advance Psychopathology Research

Recent advances in scientific techniques, particularly in psychoneuroendocrinology and functional neuroimaging, have made it clear that clinically significant antisocial behavior, such as that seen in conduct disorder, cannot be understood without reference to multiple biological systems.¹ However, the additional complexity arising from the interaction between the multiple biological systems implicated in conduct disorder has not typically been reflected in the complexity of experimental designs. Most often, studies examine only one system or subsystem at a time. Furthermore, the majority of studies of conduct disorder have not included female participants, have included few female participants, and/or have not explicitly considered biological sex in analytic strategies.² Particularly in the context of endocrinological functioning, biological sex is an important but understudied biological variable.³ Greater complexity in experimental design, incorporating data from different biological systems, and factoring in important variables such as sex will be needed moving forward to adequately model data from all of the relevant levels of analysis. This is true with respect not just to conduct disorder but to all psychopathology. The paper by Bernhard et al⁴ published in this issue is an excellent example of the types of studies that are required to grapple with the complexity of any psychiatric illness. Their study is notable for its examination of multiple endocrine systems simultaneously and for adequately incorporating biological sex as a variable into the study.

Neuroendocrine Stress Response in Female and Male Youths With Conduct Disorder and Associations With Early Adversity

OBJECTIVE

Conduct disorder (CD) involves aggressive and antisocial behavior and is associated with blunted cortisol stress response in male youths. Far less is known about cortisol stress responsivity in female youths with CD or other neuroendocrine responses in both sexes. Although CD is linked to early adversity, the possibility that neuroendocrine alterations may mediate the relationship between early adversity and CD has not been systematically investigated.

METHOD

Within the European FemNAT-CD multi-site study, salivary cortisol, testosterone, the testosterone/cortisol ratio, oxytocin, and psychological stress response to a standardized psychosocial stress test (the Trier Social Stress Test [TSST]), together with common pre- and postnatal environmental risk factors, were investigated in 130 pubertal youths with CD (63% female, 9-18 years of age) and 160 sex-, age-, and puberty-matched healthy controls (HCs).

RESULTS

The TSST induced psychological stress in both CD and HCs. In contrast, female and male youths with CD showed blunted cortisol, testosterone, oxytocin, and testosterone/cortisol stress responses compared to HCs. These blunted stress responses partly mediated the relationship between environmental risk factors and CD.

CONCLUSION

Findings from this unique sample, including many female youths with CD, provide evidence for a widespread attenuated stress responsivity of not only stress hormones, but also sex hormones and neuropeptides in CD and its subgroups (eg, with limited prosocial emotions). Results are the first to demonstrate blunted neuroendocrine stress responses in both female and male youths with CD. Early adversity may alter neuroendocrine stress responsivity. Biological mechanisms should be investigated further to pave the way for personalized intervention, thereby improving treatments for CD.

Predation Stress Causes Excessive Aggression in Female Mice with Partial Genetic Inactivation of Tryptophan Hydroxylase-2: Evidence for Altered Myelination-Related Processes

The interaction between brain serotonin (5-HT) deficiency and environmental adversity may predispose females to excessive aggression. Specifically, complete inactivation of the gene encoding tryptophan hydroxylase-2 (Tph2) results in the absence of neuronal 5-HT synthesis and excessive aggressiveness in both male and female null mutant (Tph2−/−) mice. In heterozygous male mice (Tph2+/−), there is a moderate reduction in brain 5-HT levels, and when they are exposed to stress, they exhibit increased aggression. Here, we exposed female Tph2+/− mice to a five-day rat predation stress paradigm and assessed their emotionality and social interaction/aggression-like behaviors. Tph2+/− females exhibited excessive aggression and increased dominant behavior. Stressed mutants displayed altered gene expression of the 5-HT receptors Htr1a and Htr2a, glycogen synthase kinase-3 β (GSK-3β), and c-fos as well as myelination-related transcripts in the prefrontal cortex: myelin basic protein (Mbp), proteolipid protein 1 (Plp1), myelin-associated glycoprotein (Mag), and myelin oligodendrocyte glycoprotein (Mog). The expression of the plasticity markers synaptophysin (Syp) and cAMP response element binding protein (Creb), but not AMPA receptor subunit A2 (GluA2), were affected by genotype. Moreover, in a separate experiment, naïve female Tph2+/− mice showed signs of enhanced stress resilience in the modified swim test with repeated swimming sessions. Taken together, the combination of a moderate reduction in brain 5-HT with environmental challenges results in behavioral changes in female mice that resemble the aggression-related behavior and resilience seen in stressed male mutants; additionally, the combination is comparable to the phenotype of null mutants lacking neuronal 5-HT. Changes in myelination-associated processes are suspected to underpin the molecular mechanisms leading to aggressive behavior.

Sex differences in psychiatric comorbidity and clinical presentation in youths with conduct disorder

BACKGROUND

Conduct disorder (CD) rarely occurs alone but is typically accompanied by comorbid psychiatric disorders, which complicates the clinical presentation and treatment of affected youths. The aim of this study was to investigate sex differences in comorbidity pattern in CD and to systematically explore the 'gender paradox' and 'delayed-onset pathway' hypotheses of female CD.

METHODS

As part of the FemNAT-CD multisite study, semistructured clinical interviews and rating scales were used to perform a comprehensive phenotypic characterization of 454 girls and 295 boys with CD (9-18 years), compared to 864 sex- and age-matched typically developing controls.

RESULTS

Girls with CD exhibited higher rates of current major depression, anxiety disorders, post-traumatic stress disorder and borderline personality disorder, whereas boys with CD had higher rates of current attention-deficit/hyperactivity disorder. In line with the 'gender paradox' hypothesis, relative to boys, girls with CD showed significantly more lifetime psychiatric comorbidities (incl. Alcohol Use Disorder), which were accompanied by more severe CD symptoms. Female and male youths with CD also differed significantly in their CD symptom profiles and distribution of age-of-onset subtypes of CD (i.e. fewer girls with childhood-onset CD). In line with the 'delayed-onset pathway' hypothesis, girls with adolescent-onset CD showed similar levels of dimensional psychopathology like boys with childhood-onset CD, while boys with adolescent-onset CD had the lowest levels of internalizing psychopathology.

CONCLUSIONS

Within the largest study of CD in girls performed to date, we found compelling evidence for sex differences in comorbidity patterns and clinical presentation of CD. Our findings further support aspects of the 'gender paradox' and 'delayed-onset pathway' hypotheses by showing that girls with CD had higher rates of comorbid lifetime mental disorders and functional impairments, and they usually developed CD during adolescence. These novel data on sex-specific clinical profiles of CD will be critical in informing intervention and prevention programmes.

Neuroendocrine regulation of female aggression

Classically the neurobiology of aggression has been studied exclusively in males. Thus, females have been considered mildly aggressive except during lactation. Interestingly, recent studies in rodents and humans have revealed that non-lactating females can show exacerbated and pathological aggression similarly to males. This review provides an overview of recent findings on the neuroendocrine mechanisms regulating aggressive behavior in females. In particular, the focus will be on novel rodent models of exaggerated aggression established in non-lactating females. Among the neuromodulatory systems influencing female aggression, special attention has been given to sex-steroids and sex-steroid-sensitive neuronal populations (i.e., the core nuclei of the neural pathway of aggression) as well as to the neuropeptides oxytocin and vasopressin which are major players in the regulation of social behaviors.

Female Forensic Patients May Be an Atypical Sub-type of Females Presenting Aggressive and Antisocial Behavior

The percentage of forensic psychiatric patients who are female varies from 5 to 13% in Europe, rises to 18% in England and Wales, and sits at 15% in Canada. Similarly, many fewer women than men are incarcerated in correctional facilities. While these statistics supposedly reflect less antisocial and aggressive behavior (AAB) among females than males, not all findings support this supposition. Data from prospective longitudinal studies show that aggressive and antisocial behavior onsets in childhood, and in a small group of females it remains stable across the life-span. Unlike similar males, few of these females are convicted of crimes. This article begins with a review of descriptive studies of females sentenced by criminal courts to treatment in forensic psychiatric hospitals and moves on to present evidence showing that most female AAB does not lead to criminal prosecution. Next, studies of female AAB are reviewed, noting that it onsets in early childhood and, that in a small group remains stable across the life-span. Subsequent sections of the article focus on the two most common mental disorders presented by female forensic patients, schizophrenia and borderline personality disorder, highlighting what is known about the sub-groups of women with these disorders who present AAB. The article concludes with recommendations for earlier identification by psychiatric services of women presenting mental disorders and AAB, treatments to reduce both the symptoms of their mental disorders and their life-long AAB, and the research that is needed in order to improve the effectiveness of these treatments. The real possibilities of prevention of the development of AAB, and even perhaps aspects of the mental disorders that plague female forensic patients, are described.

Subgrouping children and adolescents with disruptive behaviors: symptom profiles and the role of callous-unemotional traits

Disruptive behavior during childhood and adolescence is heterogeneous and associated with several psychiatric disorders. The identification of more homogeneous subgroups might help identify different underlying pathways and tailor treatment strategies. Children and adolescents (aged 8-18) with disruptive behaviors (N = 121) and healthy controls (N = 100) were included in a European multi-center cognition and brain imaging study. They were assessed via a battery of standardized semi-structured interviews and questionnaires. K-means cluster-model analysis was carried out to identify subgroups within the group with disruptive behaviors, based on clinical symptom profiles, callous-unemotional (CU) traits, and proactive and reactive aggression. The resulting subgroups were then compared to healthy controls with regard to these clinical variables. Three distinct subgroups were found within the group with disruptive behaviors. The High CU Traits subgroup presented elevated scores for CU traits, proactive aggression and conduct disorder (CD) symptoms, as well as a higher proportion of comorbidities (CD + oppositional defiant disorder + attention deficit hyperactivity disorder (ADHD). The ADHD and Affective Dysregulation subgroup showed elevated scores for internalizing and ADHD symptoms, as well as a higher proportion of females. The Low Severity subgroup had relatively low levels of psychopathology and aggressive behavior compared to the other two subgroups. The High CU Traits subgroup displayed more antisocial behaviors than the Low Severity subgroup, but did not differ when compared to the ADHD and Affective Dysregulation subgroup. All three subgroups differed significantly from the healthy controls in all the variables analyzed. The present study extends previous findings on subgrouping children and adolescents with disruptive behaviors using a multidimensional approach and describes levels of anxiety, affective problems, ADHD, proactive aggression and CU traits as key factors that differentiate conclusively between subgroups.

Psychopathy in women: insights from neuroscience and ways forward for research

Psychopathy is a severe form of personality disturbance, resulting in a detrimental impact on individuals, healthcare systems, and society as a whole. Until relatively recently, most research in psychopathy has focused on male samples, not least because of its link with criminal behavior and the large proportion of violent crime committed by men. However, psychopathy in women also leads to considerable problems at an individual and societal level, including substance misuse, poor treatment outcomes, and contribution to ever-increasing numbers of female prisoners. Despite this, due to relative neglect, most research into adult female psychopathy is underpowered and outdated. We argue that the field needs revitalizing, with a focus on the developmental nature of the condition and neurocognitive research. Recent work international consortia into conduct disorder in female youth-a precursor of psychopathy in female adults-gives cause for optimism. Here, we outline key strategies for enriching research in this important field with contemporary approaches to other psychiatric conditions.

Machine learning classification of conduct disorder with high versus low levels of callous-unemotional traits based on facial emotion recognition abilities

Conduct disorder (CD) with high levels of callous-unemotional traits (CD/HCU) has been theoretically linked to specific difficulties with fear and sadness recognition, in contrast to CD with low levels of callous-unemotional traits (CD/LCU). However, experimental evidence for this distinction is mixed, and it is unclear whether these difficulties are a reliable marker of CD/HCU compared to CD/LCU. In a large sample (N = 1263, 9-18 years), we combined univariate analyses and machine learning classifiers to investigate whether CD/HCU is associated with disproportionate difficulties with fear and sadness recognition over other emotions, and whether such difficulties are a reliable individual-level marker of CD/HCU. We observed similar emotion recognition abilities in CD/HCU and CD/LCU. The CD/HCU group underperformed relative to typically developing (TD) youths, but difficulties were not specific to fear or sadness. Classifiers did not distinguish between youths with CD/HCU versus CD/LCU (52% accuracy), although youths with CD/HCU and CD/LCU were reliably distinguished from TD youths (64% and 60%, respectively). In the subset of classifiers that performed well for youths with CD/HCU, fear and sadness were the most relevant emotions for distinguishing them from youths with CD/LCU and TD youths, respectively. We conclude that non-specific emotion recognition difficulties are common in CD/HCU, but are not reliable individual-level markers of CD/HCU versus CD/LCU. These findings highlight that a reduced ability to recognise facial expressions of distress should not be assumed to be a core feature of CD/HCU.

SLC25A24 gene methylation and gray matter volume in females with and without conduct disorder: an exploratory epigenetic neuroimaging study

Conduct disorder (CD), a psychiatric disorder characterized by a repetitive pattern of antisocial behaviors, results from a complex interplay between genetic and environmental factors. The clinical presentation of CD varies both according to the individual's sex and level of callous-unemotional (CU) traits, but it remains unclear how genetic and environmental factors interact at the molecular level to produce these differences. Emerging evidence in males implicates methylation of genes associated with socio-affective processes. Here, we combined an epigenome-wide association study with structural neuroimaging in 51 females with CD and 59 typically developing (TD) females to examine DNA methylation in relation to CD, CU traits, and gray matter volume (GMV). We demonstrate an inverse pattern of correlation between CU traits and methylation of a chromosome 1 region in CD females (positive) as compared to TD females (negative). The identified region spans exon 1 of the SLC25A24 gene, central to energy metabolism due to its role in mitochondrial function. Increased SLC25A24 methylation was also related to lower GMV in multiple brain regions in the overall cohort. These included the superior frontal gyrus, prefrontal cortex, and supramarginal gyrus, secondary visual cortex and ventral posterior cingulate cortex, which are regions that have previously been implicated in CD and CU traits. While our findings are preliminary and need to be replicated in larger samples, they provide novel evidence that CU traits in females are associated with methylation levels in a fundamentally different way in CD and TD, which in turn may relate to observable variations in GMV across the brain.

Positive and negative parenting in conduct disorder with high versus low levels of callous-unemotional traits

Less is known about the relationship between conduct disorder (CD), callous-unemotional (CU) traits, and positive and negative parenting in youth compared to early childhood. We combined traditional univariate analyses with a novel machine learning classifier (Angle-based Generalized Matrix Learning Vector Quantization) to classify youth (N = 756; 9-18 years) into typically developing (TD) or CD groups with or without elevated CU traits (CD/HCU, CD/LCU, respectively) using youth- and parent-reports of parenting behavior. At the group level, both CD/HCU and CD/LCU were associated with high negative and low positive parenting relative to TD. However, only positive parenting differed between the CD/HCU and CD/LCU groups. In classification analyses, performance was best when distinguishing CD/HCU from TD groups and poorest when distinguishing CD/HCU from CD/LCU groups. Positive and negative parenting were both relevant when distinguishing CD/HCU from TD, negative parenting was most relevant when distinguishing between CD/LCU and TD, and positive parenting was most relevant when distinguishing CD/HCU from CD/LCU groups. These findings suggest that while positive parenting distinguishes between CD/HCU and CD/LCU, negative parenting is associated with both CD subtypes. These results highlight the importance of considering multiple parenting behaviors in CD with varying levels of CU traits in late childhood/adolescence.

Sex-specific associations of basal steroid hormones and neuropeptides with Conduct Disorder and neuroendocrine mediation of environmental risk

Conduct Disorder (CD) is characterized by severe aggressive and antisocial behavior. The stress hormone system has frequently been investigated as a neurobiological correlate of CD, while other interacting neuroendocrine biomarkers of sex hormone or neuropeptide systems have rarely been studied, especially in females. We examined multiple basal neuroendocrine biomarkers in female and male adolescents with CD compared to healthy controls (HCs), and explored whether they mediate effects of environmental risk factors on CD. Within the FemNAT-CD study, salivary cortisol, alpha-amylase, testosterone, dehydroepiandrosterone-sulfate (DHEA-S), estradiol, progesterone, oxytocin, and arginine-vasopressin were measured under basal conditions in 166 pubertal adolescents with CD, and 194 sex-, age-, and puberty-matched HCs (60% females, 9-18 years). Further, environmental risk factors were assessed. Single hormone analyses showed higher DHEA-S, and lower estradiol and progesterone levels in both females and males with CD relative to HCs. When accounting for interactions between neuroendocrine systems, a male-specific sex hormone factor (testosterone/DHEA-S) predicted male CD, while estradiol and a stress-system factor (cortisol/alpha-amylase) interacting with oxytocin predicted female CD. Estradiol, progesterone, and oxytocin partly explained associations between early environmental risk and CD. Findings provide evidence for sex-specific associations between basal neuroendocrine measures and CD. Especially altered sex hormones (androgen increases in males, estrogen reductions in females) robustly related to CD, while basal stress-system measures did not. Early environmental risk factors for CD may act partly through their effects on the neuroendocrine system, especially in females. Limitations (e.g., basal neuroendocrine assessment, different sample sizes per sex, pubertal participants, exploratory mediation analyses) are discussed.

Cortisol response to acute psychosocial stress in ADHD compared to conduct disorder and major depressive disorder: A systematic review

BERNHARD, A., J. S. Mayer, N. Fann, and C. M. Freitag. Cortisol response to acute psychosocial stress in ADHD compared to Conduct Disorder and Major Depressive Disorder: A systematic review. NEUROSCI BIOBEHAV REV XX(X) XXX-XXX, 2020. - Heterogeneous alterations of the cortisol stress response in Attention-deficit/hyperactivity Disorder (ADHD) were recently reported by a systematic literature review. To investigate the moderating effect of frequent psychiatric comorbidities, we systematically searched for studies on cortisol stress response to psychosocial stress in ADHD compared to Conduct Disorder (CD) and Major Depressive Disorder (MDD) following PRISMA guidelines. EBSCOhost and PubMed databases were searched in July 2020, employing relevant keywords. Nineteen studies met inclusion criteria. While blunted cortisol stress response was consistently reported in individuals with CD and/or Oppositional Defiant Disorder (ODD), alterations of cortisol stress response were less pronounced in ADHD. Consistently blunted cortisol stress response in ADHD was only found in children with comorbid CD/ODD. Results on cortisol stress response in children and adolescents with MDD were mixed, and no indication for influence of comorbid MDD on cortisol stress response in ADHD was found. Taken together, altered cortisol stress response in ADHD is driven by comorbidity with disruptive behavior disorders. Limitations of previous research and suggestions for future studies are discussed.

DNA methylation signatures of aggression and closely related constructs: A meta-analysis of epigenome-wide studies across the lifespan

DNA methylation profiles of aggressive behavior may capture lifetime cumulative effects of genetic, stochastic, and environmental influences associated with aggression. Here, we report the first large meta-analysis of epigenome-wide association studies (EWAS) of aggressive behavior (N = 15,324 participants). In peripheral blood samples of 14,434 participants from 18 cohorts with mean ages ranging from 7 to 68 years, 13 methylation sites were significantly associated with aggression (alpha = 1.2 × 10-7; Bonferroni correction). In cord blood samples of 2425 children from five cohorts with aggression assessed at mean ages ranging from 4 to 7 years, 83% of these sites showed the same direction of association with childhood aggression (r = 0.74, p = 0.006) but no epigenome-wide significant sites were found. Top-sites (48 at a false discovery rate of 5% in the peripheral blood meta-analysis or in a combined meta-analysis of peripheral blood and cord blood) have been associated with chemical exposures, smoking, cognition, metabolic traits, and genetic variation (mQTLs). Three genes whose expression levels were associated with top-sites were previously linked to schizophrenia and general risk tolerance. At six CpGs, DNA methylation variation in blood mirrors variation in the brain. On average 44% (range = 3-82%) of the aggression-methylation association was explained by current and former smoking and BMI. These findings point at loci that are sensitive to chemical exposures with potential implications for neuronal functions. We hope these results to be a starting point for studies leading to applications as peripheral biomarkers and to reveal causal relationships with aggression and related traits.

Maturation of the Cardiac Autonomic Nervous System Activity in Children and Adolescents

Background

Despite the increasing interest in cardiac autonomic nervous activity, the normal development is not fully understood. The main aim was to determine the maturation of different cardiac sympathetic‐(SNS) and parasympathetic nervous system (PNS) activity parameters in healthy patients aged 0.5 to 20 years. A second aim was to determine potential sex differences.

Methods and Results

Five studies covering the 0.5‐ to 20‐year age range provided impedance‐ and electrocardiography recordings from which heart rate, different PNS‐parameters (eg, respiratory sinus arrhythmia) and an SNS‐parameter (pre‐ejection period) were collected. Age trends were computed in the mean values across 12 age‐bins and in the age‐specific variances. Age was associated with changes in mean and variance of all parameters. PNS‐activity followed a cubic trend, with an exponential increase from infancy, a plateau phase during middle childhood, followed by a decrease to adolescence. SNS‐activity showed a more linear trend, with a gradual decrease from infancy to adolescence. Boys had higher SNS‐activity at ages 11 to 15 years, while PNS‐activity was higher at 5 and 11 to 12 years with the plateau level reached earlier in girls. Interindividual variation was high at all ages. Variance was reasonably stable for SNS‐ and the log‐transformed PNS‐parameters.

Conclusions

Cardiac PNS‐ and SNS‐activity in childhood follows different maturational trajectories. Whereas PNS‐activity shows a cubic trend with a plateau phase during middle childhood, SNS‐activity shows a linear decrease from 0.5 to 20 years. Despite the large samples used, clinical use of the sex‐specific centile and percentile normative values is modest in view of the large individual differences, even within narrow age bands.

High Correspondence Between Child Behavior Checklist Rule Breaking Behavior Scale with Conduct Disorder in Males and Females

This study investigated the diagnostic utility of the Child Behavior Checklist (CBCL) Rule-Breaking Behavior scale to identify children of both sexes with conduct disorder (CD). Participants were derived from four independent datasets of children with and without attention deficit hyperactivity disorder and bipolar-I disorder of both sexes. Participants had structured diagnostic interviews with raters blinded to subject ascertainment status. Receiver operating characteristic (ROC) curves were used to examine the scale's ability to identify children with and without CD. The sample consisted of 674 participants (mean age of 11.7 ± 3.3 years, 57% male, 94% Caucasian). The interaction to test if CBCL Rule-Breaking Behavior scores identified males and females with CD differently was not significant, thus we performed ROC analysis in the combined group. The ROC analysis of the scale yielded an area under the curve of 0.9. A score of ≥ 60 on the scale correctly classified 82% of participants with CD with 85% sensitivity, 81% specificity, 48% positive predictive value, 96% negative predictive value. The CBCL Rule-Breaking Behavior scale was an efficient tool to identify children with CD.

Relational Aggression in Adolescents with Conduct Disorder: Sex Differences and Behavioral Correlates

As most research on conduct disorder (CD) has been conducted on male participants, it has been suggested that female-specific symptoms may be underestimated based on current DSM-5 criteria. In particular, relational aggression, i.e. the hurtful, often indirect, manipulation of relationships with the intention of damaging the other's social position, has been proposed as a characteristic of CD that is more common in females. In addition, sex-specific studies on correlates of relational aggressive behavior are lacking. Relational aggression may be strongly related to the correlates of proactive aggression, namely low affective empathy, and high levels of callous-unemotional (CU) traits and relational victimization. Thus, the present study investigated sex differences in relational aggression, and associations between relational aggression and correlates of proactive aggression in 662 adolescents with CD (403 females) and 849 typically-developing controls (568 females) aged 9-18 years (M = 14.74, SD = 2.34) from the European multi-site FemNAT-CD study. Females with CD showed significantly higher levels of relational aggression compared to males with CD, whereas no sex differences were seen in controls. Relational aggression was only partly related to correlates of proactive aggression in CD: Independent of sex, CU traits showed a positive association with relational aggression. In females only, cognitive, but not affective empathy, was negatively associated with relational aggression. Relational victimization was more strongly associated with relational aggression in males compared to females. Despite interesting sex specific correlates of relational aggression, effects are small and the potential clinical implications should be investigated in future studies.

Cortical thickness of the insula and prefrontal cortex relates to externalizing behavior: Cross-sectional and prospective findings

Externalizing behaviors (EBs) pertain to a diverse set of aggressive, antisocial, and potentially destructive behaviors directed toward the external environment. They range from nonclinical to clinical in severity, associated with opposition, aggression, hyperactivity, or impulsivity, and are considered a risk factor for the emergence of psychopathology later in adulthood. Focusing on community adolescents (N = 102; 49 female and 53 male adolescents; age range 12-19 years), this study aimed to explore the relations between EBs and the cortical thickness of regions of interest as well as to identify possible risk markers that could improve understanding of the EB construct. Using a mixed cross-sectional and prospective design (1-year follow-up), we report specific associations with cortical thickness of the left insular, right orbitofrontal, and left anterior cingulate cortex. Specifically, thinner left insular and right orbitofrontal cortex was associated with higher EBs, and thinner left anterior cingulate cortex predicted less reduction in EBs 1 year later. In addition, further examination of the aggression and rule-breaking subscales of the Youth/Adult Self-Report, used to assess EBs, revealed specific associations with insular subregions. Findings suggest that cortical structure morphology may significantly relate to the expression and maintenance of EBs within the general population of adolescents.

Neuropsychological Subgroups of Emotion Processing in Youths With Conduct Disorder

Background: At the group level, youths with conduct disorder (CD) show deficient emotion processing across various tasks compared to typically developing controls (TDC). But little is known about neuropsychological subgroups within the CD population, the clinical correlates of emotion processing deficits [for instance, with regard to the presence or absence of the DSM-5 Limited Prosocial Emotions (LPE) specifier], and associated risk factors. Methods: 542 children and adolescents with CD (317 girls) and 710 TDCs (479 girls), aged 9-18 years, were included from the FemNAT-CD multisite study. All participants completed three neuropsychological tasks assessing emotion recognition, emotion learning, and emotion regulation. We used a self-report measure of callous-unemotional traits to create a proxy for the LPE specifier. Results: Relative to TDCs, youths with CD as a group performed worse in all three emotion domains. But using clinically based cut-off scores, we found poor emotion recognition skills in only 23% of the participants with CD, followed by emotion regulation deficits in 18%, and emotion learning deficits in 13% of the CD group. Critically, the majority of youths with CD (~56%) did not demonstrate any meaningful neuropsychological deficit, and only a very small proportion showed pervasive deficits across all three domains (~1%). Further analyses indicate that established DSM-5 subtypes of CD are not tightly linked to neurocognitive deficits in one particular emotion domain over another (i.e., emotion recognition deficits in CD+LPE vs. emotion regulation deficits in CD-LPE). Conclusions: Findings from this large-scale data set suggest substantial neuropsychological diversity in emotion processing in the CD population and, consequently, only a subgroup of youths with CD are likely to benefit from additional behavioral interventions specifically targeting emotion processing mechanisms.

Neural correlates of theory of mind in typically-developing youth: Influence of sex, age and callous-unemotional traits

Theory of mind (ToM), or the ability to infer and predict the intentions, thoughts and beliefs of others, involves cognitive perspective taking (cognitive ToM/cToM) and understanding emotions (affective ToM/aToM). While behavioral evidence indicates that ToM is influenced by sex and age, no study has examined the influence of these variables on the neural correlates of cToM and aToM in late childhood/adolescence. Using fMRI with 35 typically-developing youths (aged 9-18 years, 12 males), we investigated the influence of sex and age on the neural correlates of cToM and aToM. We also examined how callous-unemotional traits, indexing a lack of empathy, were related to brain responses during aToM. Across both conditions, we found convergent activity in ToM network regions, such as superior temporal sulcus/temporoparietal junction (TPJ) and precuneus across males and females, but males recruited the left TPJ significantly more than females during cToM. During aToM, age was negatively correlated with brain responses in frontal, temporal and posterior midline regions, while callous-unemotional traits were positively correlated with right anterior insula responses. These results provide the first evidence in youth that sex influences the neural correlates of cToM, while age and callous-unemotional traits are specifically related to brain responses during aToM.

Friendship Quality in Youth With and Without Disruptive Behavior Disorders: The Role of Empathy, Aggression, and Callousness

Youth with disruptive behavior disorders (DBD; Oppositional defiant disorder and/or conduct disorder) are known to show impaired social relationships. Little is known about positive (PFQ) and negative best friendship quality (NFQ) in youth with DBD, and their relations with DBD specific symptoms such as aggression subtypes, empathic abilities, and callous unemotional (CU)-traits. The current study includes N = 115 youth with and N = 146 without DBD (M_age = 13.98, SD = 2.2). A diagnostic interview and self-rating questionnaires assessed ODD/CD diagnosis, friendship quality, aggression, empathy, and CU-traits. When examined on a categorical level, youth with and without DBD did not differ in friendship quality. On a dimensional level across groups, perspective taking was positively associated with PFQ. Proactive aggression was positively associated with NFQ. CU-traits in females were positively, while CU-traits in males were negatively, associated with NFQ. Results highlight that behavioral and cognitive symptoms, rather than clinical categories, are important to consider when discussing friendship qualities.

Conduct disorder

Conduct disorder (CD) is a common and highly impairing psychiatric disorder that usually emerges in childhood or adolescence and is characterized by severe antisocial and aggressive behaviour. It frequently co-occurs with attention-deficit/hyperactivity disorder (ADHD) and often leads to antisocial personality disorder in adulthood. CD affects ~3% of school-aged children and is twice as prevalent in males than in females. This disorder can be subtyped according to age at onset (childhood-onset versus adolescent-onset) and the presence or absence of callous-unemotional traits (deficits in empathy and guilt). The aetiology of CD is complex, with contributions of both genetic and environmental risk factors and different forms of interplay among the two (gene-environment interaction and correlation). In addition, CD is associated with neurocognitive impairments; smaller grey matter volume in limbic regions such as the amygdala, insula and orbitofrontal cortex, and functional abnormalities in overlapping brain circuits responsible for emotion processing, emotion regulation and reinforcement-based decision-making have been reported. Lower hypothalamic-pituitary-adrenal axis and autonomic reactivity to stress has also been reported. Management of CD primarily involves parent-based or family-based psychosocial interventions, although stimulants and atypical antipsychotics are sometimes used, especially in individuals with comorbid ADHD.

Post-weaning social isolation exacerbates aggression in both sexes and affects the vasopressin and oxytocin system in a sex-specific manner

Post-weaning social isolation (PWSI) is known to induce exaggerated and abnormal aggression in male rats. Here we aimed to assess the effects of PWSI on aggressiveness and social behavior in both male and female rats. Furthermore, we evaluated how PWSI affects the central oxytocin (OXT) and vasopressin (AVP) systems in both sexes. Wistar rats were isolated (IS) or group housed (GH) in same-sex groups immediately after weaning. After seven weeks, rats underwent an intruder test to assess aggression. In one group, brains were immediately dissected afterwards for in situ hybridization and receptor autoradiography. The other group underwent additional anxiety-like and social behavior tests. PWSI induced increased (abnormal) aggression and impaired social memory in both sexes. Especially IS females exhibited abnormal aggression towards juveniles. Furthermore, PWSI increased OXT mRNA expression in the paraventricular nucleus of the hypothalamus (PVN) and decreased OXTR binding in the anterior portion of the nucleus accumbens (NAcc), independent of the sex. V1a receptor binding was decreased in the lateral hypothalamus (LH) and dentate gyrus (DG) in IS rats, regardless of sex. However, V1a receptor binding in the anterior portion of the bed nucleus of stria terminalis (BNSTa) was decreased in IS females but increased in IS males. Taken together, our data support PWSI as a reliable model to exacerbate aggression not only in male but also in female rats. In addition, OXT receptors in the NAcca and V1a receptors in the LH, DG, and BNSTa may play a role in the link between PWSI and aggression. This article is part of the Special Issue entitled 'Current status of the neurobiology of aggression and impulsivity'.

Towards a neurobiology of female aggression

Although many people think of aggression as a negative or undesirable emotion, it is a normal part of many species' repertoire of social behaviors. Purposeful and controlled aggression can be adaptive in that it warns other individuals of perceived breaches in social contracts with the goal of dispersing conflict before it escalates into violence. Aggression becomes maladaptive, however, when it escalates inappropriately or impulsively into violence. Despite ample data demonstrating that impulsive aggression and violence occurs in both men and women, aggression has historically been considered a uniquely masculine trait. As a result, the vast majority of studies attempting to model social aggression in animals, particularly those aimed at understanding the neural underpinnings of aggression, have been conducted in male rodents. In this review, we summarize the state of the literature on the neurobiology of social aggression in female rodents, including social context, hormonal regulation and neural sites of aggression regulation. Our goal is to put historical research in the context of new research, emphasizing studies using ecologically valid methods and modern sophisticated techniques. This article is part of the Special Issue entitled 'Current status of the neurobiology of aggression and impulsivity'.

Altered Neuronal Responses During an Affective Stroop Task in Adolescents With Conduct Disorder

Conduct disorder (CD) is a psychiatric disorder of childhood and adolescence which has been linked to deficient emotion processing and regulation. The behavioral and neuronal correlates targeting the interaction of emotion processing and response inhibition are still under investigation. Whole-brain event-related fMRI was applied during an affective Stroop task in 39 adolescents with CD and 39 typically developing adolescents (TD). Participants were presented with an emotional stimulus (negative/neutral) followed by a Stroop task with varying cognitive load (congruent/incongruent/blank trials). fMRI analysis included standard preprocessing, region of interest analyses (amygdala, insula, ventromedial prefrontal cortex) and whole-brain analyses based on a 2(group) × 2(emotion) × 3(task) full-factorial ANOVA. Adolescents with CD made significantly more errors, while reaction times did not significantly differ compared to TD. Additionally, we observed a lack of downregulation of left amygdala activity in response to incongruent trials and increased anterior insula activity for CD relative to TD during affective Stroop task processing [cluster-level family-wise error-corrected (p < 0.05)]. Even though no three-way interaction (group × emotion × task) interaction was detected, the findings presented still provide evidence for altered neuronal underpinnings of the interaction of emotion processing and response inhibition in CD. Moreover, our results may corroborate previous evidence of emotion dysregulation as a core dysfunction in CD. Future studies shall focus on investigating the interaction of emotion processing and response inhibition in CD subgroups (e.g., variations in callous-unemotional traits, impulsivity, or anxiety).