Developmental psychopathology and neurobiology of aggression

Dopamine transporter blockade during adolescence increases adult dopamine function, impulsivity, and aggression

Sensitive developmental periods shape neural circuits and enable adaptation. However, they also engender vulnerability to factors that can perturb developmental trajectories. An understanding of sensitive period phenomena and mechanisms separate from sensory system development is still lacking, yet critical to understanding disease etiology and risk. The dopamine system is pivotal in controlling and shaping adolescent behaviors, and it undergoes heightened plasticity during that time, such that interference with dopamine signaling can have long-lasting behavioral consequences. Here we sought to gain mechanistic insight into this dopamine-sensitive period and its impact on behavior. In mice, dopamine transporter (DAT) blockade from postnatal (P) day 22 to 41 increases aggression and sensitivity to amphetamine (AMPH) behavioral stimulation in adulthood. Here, we refined this sensitive window to P32-41 and identified increased firing of dopaminergic neurons in vitro and in vivo as a neural correlate to altered adult behavior. Aggression can result from enhanced impulsivity and cognitive dysfunction, and dopamine regulates working memory and motivated behavior. Hence, we assessed these behavioral domains and found that P32-41 DAT blockade increases impulsivity but has no effect on cognition, working memory, or motivation in adulthood. Lastly, using optogenetics to drive dopamine neurons, we find that increased VTA but not SNc dopaminergic activity mimics the increase in impulsive behavior in the Go/NoGo task observed after adolescent DAT blockade. Together our data provide insight into the developmental origins of aggression and impulsivity that may ultimately improve diagnosis, prevention, and treatment strategies for related neuropsychiatric disorders.

Alcohol, Aggression, and Violence: From Public Health to Neuroscience

Alcohol has been associated with violent crimes and domestic violence across many nations. Various etiological factors were linked to chronic alcohol use and violence including psychiatric comorbidities of perpetrators such as personality disorders, mood disorders, and intermittent explosive disorders. Aggression is the precursor of violence and individuals prone to aggressive behaviors are more likely to commit impulsive violent crimes, especially under the influence of alcohol. Findings from brain studies indicate long-term alcohol consumption induced morphological changes in brain regions involved in self-control, decision-making, and emotional processing. In line with this, the inherent dopaminergic and serotonergic anomalies seen in aggressive individuals increase their susceptibility to commit violent crimes when alcohol present in their system. In relation to this, this article intends to investigate the influence of alcohol on aggression with sociopsychological and neuroscientific perspectives by looking into comorbidity of personality or mood disorders, state of the mind during alcohol consumption, types of beverages, environmental trigger, neurochemical changes, and gender differences that influence individual responses to alcohol intake and susceptibility to intoxicated aggression.

Acting with shared intentions: A systematic review on joint action coordination in Autism Spectrum Disorder

BACKGROUND

Joint actions, described as a form of social interaction in which individuals coordinate their actions in space and time to bring about a change in the environment, rely on sensory-motor processes that play a role in the development of social skills. Two brain networks, associated with "mirroring" and "mentalizing", are engaged during these actions: the mirror neuron and the theory of mind systems. People with autism spectrum disorder (ASD) showed impairment in interpersonal coordination during joint actions. Studying joint action coordination in ASD will contribute to clarify the interplay between sensory-motor and social processes throughout development and the interactions between the brain and the behavior.

METHOD

This review focused on empirical studies that reported behavioral and kinematic findings related to joint action coordination in people with ASD.

RESULTS

Literature on mechanisms involved in the joint action coordination impairment in ASD is still limited. Data are controversial. Different key-components of joint action coordination may be impaired, such as cooperative behavior, temporal coordination, and motor planning.

CONCLUSIONS

Interpersonal coordination during joint actions relies on early sensory-motor processes that have a key role in guiding social development. Early intervention targeting the sensory-motor processes involved in the development of joint action coordination could positively support social skills.

Longitudinal Trajectories of Hair Cortisol: Hypothalamic-Pituitary-Adrenal Axis Dysfunction in Early Childhood

The objective of this study was to examine if longitudinal trajectories of hair cortisol concentrations (HCC) measured at two or three yearly time points can identify 1-3 year old children at risk for altered hypothalamic-pituitary-adrenal (HPA)-axis function due to early life stress (ELS). HCC was measured (N = 575) in 265 children using a validated enzyme-linked immunosorbent assay. Hair was sampled in Clinic Visits (CV) centered at years 1, 2, and 3 (n = 45); 1 and 2 (n = 98); 1 and 3 (n = 27); 2 and 3 (n = 95). Log-transformed HCC values were partitioned using latent class mixed models (LCMM) to minimize the Bayesian Information Criterion. Multivariable linear mixed effects models for ln-HCC as a function of fixed effects for age in months and random effects for participants (to account for repeated measures) were generated to identify the factors associated with class membership. Children in Class 1 (n = 69; 9% Black) evidenced declining ln-HCC across early childhood, whereas Class 2 members (n = 196; 43% Black) showed mixed trajectories. LCMM with only Class 2 members revealed Class 2A (n = 17, 82% Black) with sustained high ln-HCC and Class 2B (n = 179, 40% Blacks) with mixed ln-HCC profiles. Another LCMM limited to only Class 2B members revealed Class 2B1 (n = 65, 57% Black) with declining ln-HCC values (at higher ranges than Class 1), and Class 2B2 (n = 113, 30% Black) with sustained high ln-HCC values. Class 1 may represent hair cortisol trajectories associated with adaptive HPA-axis profiles, whereas 2A, 2B1, and 2B2 may represent allostatic load with dysregulated profiles of HPA-axis function in response to varying exposures to ELS. Sequential longitudinal hair cortisol measurements revealed the allostatic load associated with ELS and the potential for developing maladaptive or dysregulated HPA-axis function in early childhood.

Associations between cooperation, reactive aggression and social impairments among boys with autism spectrum disorder

Cooperation is a fundamental human ability that seems to be inversely related to aggressive behaviour in typical development. However, there is no knowledge whether similar association holds for children with autism spectrum disorder. A total of 27 boys with autism spectrum disorder and their gender, age and total score intelligence matched controls were studied in order to determine associations between cooperation, reactive aggression and autism spectrum disorder-related social impairments. The participants performed a modified version of the Prisoner's Dilemma task and the Pulkkinen Aggression Machine which measure dimensions of trust, trustworthiness and self-sacrifice in predisposition to cooperate, and inhibition of reactive aggression in the absence and presence of situational cues, respectively. Autism spectrum disorder severity-related Autism Diagnostic Interview-algorithm scores were ascertained by interviewing the parents of the participants with a semi-structured parental interview (Developmental, Dimensional and Diagnostic Interview). The results showed that albeit the boys with autism spectrum disorder were able to engage in reciprocation and cooperation regardless of their social impairments, their cooperativeness was positively associated with lower levels of reactive aggression and older age. Thus, strengthening inhibition mechanisms that regulate reactive aggression might make boys with autism spectrum disorder more likely to prefer mutual gain over self-interest in cooperation.

Development of self-inflicted injury: Comorbidities and continuities with borderline and antisocial personality traits

Self-inflicted injury (SII) is a continuum of intentionally self-destructive behaviors, including nonsuicidal self-injuries, suicide attempts, and death by suicide. These behaviors are among the most pressing yet perplexing clinical problems, affecting males and females of every race, ethnicity, culture, socioeconomic status, and nearly every age. The complexity of these behaviors has spurred an immense literature documenting risk and vulnerability factors ranging from individual to societal levels of analysis. However, there have been relatively few attempts to articulate a life span developmental model that integrates ontogenenic processes across these diverse systems. The objective of this review is to outline such a model with a focus on how observed patterns of comorbidity and continuity can inform developmental theories, early prevention efforts, and intervention across traditional diagnostic boundaries. Specifically, when SII is viewed through the developmental psychopathology lens, it becomes apparent that early temperamental risk factors are associated with risk for SII and a range of highly comorbid conditions, such as borderline and antisocial personality disorders. Prevention efforts focused on early-emerging biological and temperamental contributors to psychopathology have great potential to reduce risk for many presumably distinct clinical problems. Such work requires identification of early biological vulnerabilities, behaviorally conditioned social mechanisms, as well as societal inequities that contribute to self-injury and underlie intergenerational transmission of risk.

Epilepsy, Antiepileptic Drugs, and Aggression: An Evidence-Based Review

Antiepileptic drugs (AEDs) have many benefits but also many side effects, including aggression, agitation, and irritability, in some patients with epilepsy. This article offers a comprehensive summary of current understanding of aggressive behaviors in patients with epilepsy, including an evidence-based review of aggression during AED treatment. Aggression is seen in a minority of people with epilepsy. It is rarely seizure related but is interictal, sometimes occurring as part of complex psychiatric and behavioral comorbidities, and it is sometimes associated with AED treatment. We review the common neurotransmitter systems and brain regions implicated in both epilepsy and aggression, including the GABA, glutamate, serotonin, dopamine, and noradrenaline systems and the hippocampus, amygdala, prefrontal cortex, anterior cingulate cortex, and temporal lobes. Few controlled clinical studies have used behavioral measures to specifically examine aggression with AEDs, and most evidence comes from adverse event reporting from clinical and observational studies. A systematic approach was used to identify relevant publications, and we present a comprehensive, evidence-based summary of available data surrounding aggression-related behaviors with each of the currently available AEDs in both adults and in children/adolescents with epilepsy. A psychiatric history and history of a propensity toward aggression/anger should routinely be sought from patients, family members, and carers; its presence does not preclude the use of any specific AEDs, but those most likely to be implicated in these behaviors should be used with caution in such cases.

Social Ecological Determinants of Substance Use Treatment Entry Among Serious Juvenile Offenders From Adolescence Through Emerging Adulthood

PURPOSE

To examine the social-ecological determinants of substance use treatment entry among serious juvenile offenders over a 7 year period. Using the social-ecological framework, relevant predictors of substance use from the literature were used to assess risk (and protective) factors at the individual, parental, peer and neighborhood level.

METHOD

Serious juvenile offenders (N=1354, M_{age baseline}=16.0 years, SD=1.14) were prospectively followed over 7 years (M_{age Conclusion}=23.0 years, SD=1.15). Cox regression with time invariant and time varying predictors was used to predict time to first substance use treatment entry.

RESULTS

Results for each dimension, separately, varied slightly from the full model. In the full model peer delinquency, peer arrests, post-traumatic stress disorder (PTSD), impulse control, temperament, and emotional regulation remained salient risk (and protective) factors for treatment entry.

CONCLUSION

Associating with more deviant peers and having more of your peers arrested over the 7 year study period was associated with substantial increase in time to treatment entry. Furthermore, one of the strongest risk factors for treatment entry was a PTSD diagnosis. Treatment implications are discussed regarding peer affiliation and PTSD symptomology as well as potential neurological and biological contributors to increased risk for treatment entry.

Monoamine-sensitive developmental periods impacting adult emotional and cognitive behaviors

Development passes through sensitive periods, during which plasticity allows for genetic and environmental factors to exert indelible influence on the maturation of the organism. In the context of central nervous system development, such sensitive periods shape the formation of neurocircuits that mediate, regulate, and control behavior. This general mechanism allows for development to be guided by both the genetic blueprint as well as the environmental context. While allowing for adaptation, such sensitive periods are also vulnerability windows during which external and internal factors can confer risk to disorders by derailing otherwise resilient developmental programs. Here we review developmental periods that are sensitive to monoamine signaling and impact adult behaviors of relevance to psychiatry. Specifically, we review (1) a serotonin-sensitive period that impacts sensory system development, (2) a serotonin-sensitive period that impacts cognition, anxiety- and depression-related behaviors, and (3) a dopamine- and serotonin-sensitive period affecting aggression, impulsivity and behavioral response to psychostimulants. We discuss preclinical data to provide mechanistic insight, as well as epidemiological and clinical data to point out translational relevance. The field of translational developmental neuroscience has progressed exponentially providing solid conceptual advances and unprecedented mechanistic insight. With such knowledge at hand and important methodological innovation ongoing, the field is poised for breakthroughs elucidating the developmental origins of neuropsychiatric disorders, and thus understanding pathophysiology. Such knowledge of sensitive periods that determine the developmental trajectory of complex behaviors is a necessary step towards improving prevention and treatment approaches for neuropsychiatric disorders.

An expanded approach to batterer intervention programs incorporating neuroscience research

Batterer Intervention Programs have been critiqued for failing to incorporate treatment strategies that are supported by neurobiology research. This article reviews findings that have informed the treatment of disorders that are strongly represented among perpetrators of intimate violence, such as addiction, posttraumatic stress disorder, mood, anxiety, and personality disorders. The article argues for an expanded perspective that recognizes the relationships among childhood trauma, emotional regulation impairment, and intimate partner violence. Recommendations and ways to draw on emerging knowledge to invigorate existing programs are provided.

Altered functional protein networks in the prefrontal cortex and amygdala of victims of suicide

Probing molecular brain mechanisms related to increased suicide risk is an important issue in biological psychiatry research. Gene expression studies on post mortem brains indicate extensive changes prior to a successful suicide attempt; however, proteomic studies are scarce. Thus, we performed a DIGE proteomic analysis of post mortem tissue samples from the prefrontal cortex and amygdala of suicide victims to identify protein changes and biomarker candidates of suicide. Among our matched spots we found 46 and 16 significant differences in the prefrontal cortex and amygdala, respectively; by using the industry standard t test and 1.3 fold change as cut off for significance. Because of the risk of false discoveries (FDR) in these data, we also made FDR adjustment by calculating the q-values for all the t tests performed and by using 0.06 and 0.4 as alpha thresholds we reduced the number of significant spots to 27 and 9 respectively. From these we identified 59 proteins in the cortex and 11 proteins in the amygdala. These proteins are related to biological functions and structures such as metabolism, the redox system, the cytoskeleton, synaptic function, and proteolysis. Thirteen of these proteins (CBR1, DPYSL2, EFHD2, FKBP4, GFAP, GLUL, HSPA8, NEFL, NEFM, PGAM1, PRDX6, SELENBP1 and VIM,) have already been suggested to be biomarkers of psychiatric disorders at protein or genome level. We also pointed out 9 proteins that changed in both the amygdala and the cortex, and from these, GFAP, INA, NEFL, NEFM and TUBA1 are interacting cytoskeletal proteins that have a functional connection to glutamate, GABA, and serotonin receptors. Moreover, ACTB, CTSD and GFAP displayed opposite changes in the two examined brain structures that might be a suitable characteristic for brain imaging studies. The opposite changes of ACTB, CTSD and GFAP in the two brain structures were validated by western blot analysis.

Aggression in borderline personality disorder: evidence for increased risk and clinical predictors

This article aimed to systematically review the current literature regarding elevated risk of aggression in borderline personality disorder (BPD) and to review factors that differentiate aggressive from nonaggressive individuals with BPD. It has done so via a systematic review of the literature using Ovid MEDLINE and PsycINFO from 1980 to June 2010. Results indicate that BPD does not appear to be independently associated with increased risk of violence in the general population. History of childhood maltreatment, history of violence or criminality, and comorbid psychopathy or antisocial personality disorder appear to be predictors of violence in patients with BPD. This review concludes that the current evidence suggests that patients with BPD are not more violent than individuals in the general population. More studies are needed on factors that predict risk of aggression at an individual level.

The psychopharmacology of aggressive behavior: a translational approach: part 1: neurobiology

Patients with mental disorders are at an elevated risk for developing aggressive behavior. In the last 19 years, the psychopharmacological treatment of aggression has changed dramatically because of the introduction of atypical antipsychotics into the market and the increased use of anticonvulsants and lithium in the treatment of aggressive patients.Using a translational medicine approach, this review (part 1 of 2) examines the neurobiology of aggression, discussing the major neurotransmitter systems implicated in its pathogenesis, namely, serotonin, glutamate, norepinephrine, dopamine, and γ-aminobutyric acid, and also their respective receptors. The preclinical and clinical pharmacological studies concerning the role of these neurotransmitters have been reviewed, as well as research using transgenic animal models. The complex interaction among these neurotransmitters occurs at the level of brain areas and neural circuits such as the orbitoprefrontal cortex, anterior cortex, amygdala, hippocampus, periaqueductal gray, and septal nuclei, where the receptors of these neurotransmitters are expressed. The neurobiological mechanism of aggression is important to understand the rationale for using atypical antipsychotics, anticonvulsants, and lithium in treating aggressive behavior. Further research is necessary to establish how these neurotransmitter systems interact with brain circuits to control aggressive behavior at the intracellular level.

Borderline personality traits and adult attention-deficit hyperactivity disorder symptoms: a genetic analysis of comorbidity

Previous research has established the comorbidity of adult Attention-Deficit Hyperactivity Disorder (ADHD) with different personality disorders including Borderline Personality Disorder (BPD). The association between adult ADHD and BPD has primarily been investigated at the phenotypic level and not yet at the genetic level. The present study investigates the genetic and environmental contributions to the association between borderline personality traits (BPT) and ADHD symptoms in a sample of 7,233 twins and siblings (aged 18-90 years) registered with the Netherlands Twin Register and the East Flanders Prospective Twin Survey (EFPTS) . Participants completed the Conners' Adult ADHD Rating Scales (CAARS-S:SV) and the Personality Assessment Inventory-Borderline Features Scale (PAI-BOR). A bivariate genetic analysis was performed to determine the extent to which genetic and environmental factors influence variation in BPT and ADHD symptoms and the covariance between them. The heritability of BPT and ADHD symptoms was estimated at 45 and 36%, respectively. The remaining variance in BPT and ADHD symptoms was explained by unique environmental influences. The phenotypic correlation between BPT and ADHD symptoms was estimated at r = 0.59, and could be explained for 49% by genetic factors and 51% by environmental factors. The genetic and environmental correlations between BPT and ADHD symptoms were 0.72 and 0.51, respectively. The shared etiology between BPT and ADHD symptoms is thus a likely cause for the comorbidity of the two disorders.

Neurobiological and psychopathological variables related to emotional instability: a study of their capability to discriminate patients with bulimia nervosa from healthy controls

OBJECTIVE

To analyze the capability of a set of neurobiological and psychopathological variables to discriminate bulimia nervosa (BN) patients from healthy controls.

METHOD

Seventy-five female patients with purging BN and 30 healthy controls were compared for psychopathology (impulsivity, borderline personality traits, depressive symptoms and self-defeating personality traits) and neurobiological parameters reflecting hypothalamic-pituitary-adrenal axis activity (morning serum cortisol before and after dexamethasone) and monoamine activity (24-hour urinary excretion of norepinephrine, serotonin, dopamine, and their main metabolites: 3-methoxy-4-hydroxyphenylglycol, 5-hydroxyindoleacetic acid, and homovanillic acid). Furthermore, the relationships between the 2 sets of variables were compared in the 2 samples.

RESULTS

BN patients displayed higher impulsivity, more severe depressive features, and more borderline and self-defeating personality traits than controls. The 4 psychopathological variables were strongly interrelated in patients, whereas only depressive features correlated with self-defeating personality traits in controls. Patients had lower 24-hour excretion of serotonin and dopamine than controls, as well as lower ability to suppress cortisol. The relations between the biochemical and the psychopathological variables were only significant in the BN patients, but not in the control group. When discriminant analysis methods were applied, patients and controls differed for psychopathology (impulsive behaviors and borderline personality traits) and biological parameters (baseline cortisol and dopamine excretion), but when the variables were analyzed together, the differences in neurobiological parameters appeared as mediated by the psychopathological status.

DISCUSSION

Our results suggest that hypothalamic-pituitary-adrenal axis activity, dopamine activity and other biological parameters are worthy of further study as potential dimensional markers of BN, although they seem to depend on the psychopathological status of the patients, in such a way that the psychopathological items associated with emotional instability (impulsivity and borderline personality traits) seem to be more reliable as clinical markers at the time being.

Developmental predictors of an impulsive-aggressive phenotype

In hamsters, individual differences in offensive aggression are associated with impulsive choice, leading to the characterization of a distinct impulsive-aggressive phenotype. This study had two goals: to determine the developmental trajectory of the maturation of this phenotype and to address its parental lineage. Interestingly, individuals most aggressive as adults were less likely to attack in early puberty. However, looking at the transition of agonistic behavior from play fighting to adult aggression, impulsive-aggressive individuals were less likely to engage in play fighting attacks and more likely to engage in more mature agonistic behavior. Additionally, parental lineages were compared for the aggressive responses expressed by their adult offspring. Most impulsive-aggressive individuals were offspring of few select males, which were more likely to produce this phenotype, without an association with females or specific litters. These findings identify an abnormal and accelerated development of agonistic behavior in impulsive-aggressive individuals and a likelihood of heritability.

Support for religio-political aggression among teenaged boys in Gaza: Part I: psychological findings

Politically aggressive militant groups usually rely on support from a larger community, although evidence suggests that only some members of that larger community support that aggression. A major subtype of political aggression is that associated with religious differences--or Religio-Political Aggression (RPA). Little previous research has explored demographic or psychological factors that might distinguish supporters from non-supporters of RPA. In an exploratory study, we investigated whether factors previously associated with aggression might correlate with support for RPA in the case of the Israeli/Palestinian conflict. During the second intifada, fifty-two 14-year-old Palestinian boys in Gaza completed self-report measures of life events, emotional status, and political attitudes. Teenaged boys who reported family members having been wounded or killed by the Israeli Defense Forces (IDF) expressed greater support for RPA (t(50) = -2.30, P = .026). In addition, boys who felt their group was treated unjustly reported greater support for RPA compared with those who did not (t(50) = -2.273, P = .027). Implications of these preliminary data are discussed.

Efficacy and tolerability of duloxetine in the treatment of patients with borderline personality disorder: a pilot study

Guidelines of the American Psychiatric Association for borderline personality disorder (BPD) indicate selective serotonin reuptake inhibitors and the serotonin and noradrenaline reuptake inhibitor (SNRI) venlafaxine for treating affective dysregulation and impulsive behavioural dyscontrol symptoms. The SNRI duloxetine has been studied in patients with major depression, generalized anxiety disorder and fibromyalgia, showing particular efficacy on somatic complaints. This study investigates duloxetine in the treatment of patients with BPD. Eighteen outpatients with a DSM-IV-TR diagnosis of BPD were treated with open-label duloxetine, 60 mg/day, for 12 weeks. Patients were assessed at baseline, week 4 and 12 with the CGI Severity item, the BPRS, the HAM-D, the HAM-A, the SOFAS, the BPD Severity Index (BPDSI) and the HSCL-90-Somatization Subscale (HSCL-90 SOM). Adverse effects were evaluated using the Dosage Record Treatment Emergent Symptom Scale. Statistics were performed with the analysis of variance. Significant P values were <or=0.05. Fourteen patients completed the study. Four patients (22.2%) discontinued treatment in the first 4 weeks because of non-compliance. A significant change was found for: BPRS, HAM-D, SOFAS, BPDSI total score and items 'impulsivity', 'outbursts of anger' and 'affective instability' and HSCL-90 SOM. Adverse effects were mild headache and nausea. Initial results suggest that duloxetine is an effective and well-tolerated treatment for BPD, with positive effects on somatic symptoms.

[Neurobiological aspects of reactive and proactive violence in antisocial personality disorder and "psychopathy"]

Impulsive-reactive violent offenders show increased autonomic activity in response to negative emotional and threatening stimuli. A volume reduction and/or activity decrease of frontal brain structures associated with impulse control and the regulation of fear and anger are likewise found in combination with a fear-related hyperactivity of the amygdala. In addition, impulsive aggression is facilitated by variants of gene polymorphisms influencing the serotonergic system. Conversely, proactive-instrumental violent offender with psychopathy, who are characterized by a lack of empathy and remorse, demonstrate an autonomic hypo-responsivity as well as dysfunctions of the amygdala and of cortical regions related to empathic and social behavior. Developmentally, aggressive children exhibit temperamental differences from early childhood on that are characteristic of a developmental pathway towards either reactive or proactive violence later in life. Exposure to negative environmental factors like ineffective parenting or childhood maltreatment has been related to a heightened risk for developing reactive violence. A developmental trajectory of proactive violence, however, has been related to a mostly genetically determined callous unemotional temperament of the child that disrupts the parental socialization efforts during childhood.

Multifinality in the development of personality disorders: a Biology x Sex x Environment interaction model of antisocial and borderline traits

Although antisocial personality disorder (ASPD) is more common among males and borderline PD (BPD) is more common among females, some authors have suggested that the two disorders reflect multifinal outcomes of a single etiology. This assertion is based on several overlapping symptoms and features, including trait impulsivity, emotional lability, high rates of depression and suicide, and a high likelihood of childhood abuse and/or neglect. Furthermore, rates of ASPD are elevated in the first degree relatives of those with BPD, and concurrent comorbidity rates for the two disorders are high. In this article, we present a common model of antisocial and borderline personality development. We begin by reviewing issues and problems with diagnosing and studying PDs in children and adolescents. Next, we discuss dopaminergic and serotonergic mechanisms of trait impulsivity as predisposing vulnerabilities to ASPD and BPD. Finally, we extend shared risk models for ASPD and BPD by specifying genetic loci that may confer differential vulnerability to impulsive aggression and mood dysregulation among males and impulsive self-injury and mood dysregulation among females. Although the precise mechanisms of these sex-moderated genetic vulnerabilities remain poorly understood, they appear to interact with environmental risk factors including adverse rearing environments to potentiate the development of ASPD and BPD.

Modulation of stress by imidazoline binding sites: implications for psychiatric disorders

In this review, we present evidence for the involvement of imidazoline binding sites (IBS) in modulating responses to stress, through central control of monoaminergic and hypothalamo-pituitary-adrenal (HPA) axis activity. Pharmacological and physiological evidence is presented for differential effects of different IBS subtypes on serotoninergic and catecholaminergic pathways involved in control of basal and stress-stimulated HPA axis activity. IBS ligands can modulate behavioural and neuroendocrine responses in animal models of stress, depression and anxiety, and a body of evidence exists for alterations in central IBS expression in psychiatric patients, which can be normalised partially or fully by treatment with antidepressants. Dysfunction in monoaminergic systems and the HPA axis under basal and stress-induced activation has been extensively reported in psychiatric illnesses. On the basis of the literature, we suggest a potential therapeutic role for selective IBS ligands in the treatment of depression and anxiety disorders.

Atypical empathic responses in adolescents with aggressive conduct disorder: a functional MRI investigation

Because youth with aggressive conduct disorder (CD) often inflict pain on others, it is important to determine if they exhibit atypical empathic responses to viewing others in pain. In this initial functional magnetic resonance imaging (fMRI) study, eight adolescents with aggressive CD and eight matched controls with no CD symptoms were scanned while watching animated visual stimuli depicting other people experiencing pain or not experiencing pain. Furthermore, these situations involved either an individual whose pain was caused by accident or an individual whose pain was inflicted on purpose by another person. After scanning, participants rated how painful the situations were. In both groups the perception of others in pain was associated with activation of the pain matrix, including the ACC, insula, somatosensory cortex, supplementary motor area and periaqueductal gray. The pain matrix was activated to a specific extent in participants with CD, who also showed significantly greater amygdala, striatal, and temporal pole activation. When watching situations in which pain was intentionally inflicted, control youth exhibited signal increase in the medial prefrontal cortex, lateral orbitofrontal cortex, and right temporo-parietal junction, whereas youth with CD only exhibited activation in the insula and precentral gyrus. Furthermore, connectivity analyses demonstrated that youth with CD exhibited less amygdala/prefrontal coupling when watching pain inflicted by another than did control youth. These preliminary findings suggest that youth with aggressive CD exhibit an atypical pattern of neural response to viewing others in pain that should be explored in further studies.

Infusing neuroscience into the study and prevention of drug misuse and co-occurring aggressive behavior

The etiology of behavioral precursors to substance misuse and aggression is viewed from the perspective of a developmental, multifactorial model of complex disorders. Beginning at conception, genetic and environmental interactions have potential to produce a sequence of behavioral phenotypes during development that bias the trajectory toward high-risk outcomes. One pathway is theorized to emanate from a deviation in neurological development that predisposes children to affective and cognitive delays or impairments that, in turn, generate dysregulatory behaviors. The plasticity of these neurobiological systems is highly relevant to the prevention sciences; their functions are reliant upon environmental inputs and can be altered, for better or for worse, contingent upon the nature of the inputs. Thus, social contextual factors confer significant influence on the development of this neural network and behavioral outcomes by increasing risk for, or protecting (1) against, dysregulatory outcomes. A well-designed intervention can exploit the brain's plasticity by targeting biological and social factors at sensitive time points to positively influence emergent neurobiological functions and related behaviors. Accordingly, prevention research is beginning to focus on perturbations in developmental neural plasticity during childhood that increase the likelihood of risky behaviors and may also moderate intervention effects on behavior. Given that the more complex features of neurobiological functions underlying drug misuse and aggression (e.g., executive cognitive function, coping skills, affect regulation) do not coalesce until early adulthood when prefrontal-limbic brain networks consolidate, it is critical that mechanisms underlying developmental risk factors are identified. An empirically driven prevention approach, thus, may benefit from consideration of (i) the type, effect, and developmental timing of the environmental impact on the brain, and (ii) the type and effect on brain function, and developmental timing of the intervention. This translational approach promises to eventually offer some direction for the design of effective interventions to prevent drug misuse and concomitant aggression.

Sex, aggression and impulse control: an integrative account

There is evidence that the male sex and a personality style characterized by low self-control/high impulsivity and a propensity for negative emotionality increase the risk for impulsive aggressive, antisocial and criminal behavior. This article aims at identifying neurobiological factors underlying this association. It is concluded that the neurobiological correlates of impulsive aggression act through their effects on the ability to modulate impulsive expression more generally, and that sex-related differences in the neurobiological correlates of impulse control and emotion regulation mediate sex differences in direct aggression. A model is proposed that relates impulse control and its neurobiological correlates to sex differences in direct aggression.

Opposite effects of maternal separation on intermale and maternal aggression in C57BL/6 mice: link to hypothalamic vasopressin and oxytocin immunoreactivity

Early life stress, in particular child abuse and neglect, is an acknowledged risk factor for the development of pathological anxiety and aggression. In rodents, 3-h daily maternal separation (MS) during the first 2 weeks of life is an established animal model of early life stress and has repeatedly been shown to increase anxiety and stress responsiveness in adulthood. However, preclinical studies on the effects of postnatal stress on adult aggression are limited. The present study investigated whether MS affects intermale aggression and/or maternal aggression in C57BL/6 mice. In both adult male and virgin female mice, MS elevated anxiety-related behavior as tested on the elevated plus-maze, in the open field and during novel object exploration. The latency to attack an unknown male intruder, as assessed with the resident-intruder test, was significantly longer in MS male mice compared with control male mice. In contrast, the latency to attack a novel male intruder was significantly shorter in MS females compared with control females on days 3 and 5 of lactation. These opposite effects of MS can be explained by the fact that intermale and maternal aggression are two different forms of aggression, and hence, might be modulated by different neurobiological pathways. Indeed, in the paraventricular nucleus of the hypothalamus, MS was found to selectively increase vasopressin immunoreactivity in males, whereas MS selectively decreased oxytocin immunoreactivity in lactating females. In conclusion, MS has long-lasting and differential effects on adult intermale and maternal aggression in C57BL/6 mice. Alterations in hypothalamic vasopressin and oxytocin immunoreactivity may, in part, underlie the opposite effects of MS on intermale and maternal aggression. The MS paradigm represents a promising animal model to reveal underlying mechanisms of aggressive behavioral dysfunctions associated with early life stress.

Social conflict models: can they inform us about human psychopathology?

Social conflict models have been proposed as a powerful way to investigate basic questions of how brain and behavior are altered by social experience. Social defeat, in particular, appears to be a major stressor for most species, and in humans, this stressor is thought to play an important role in the onset of a variety of psychiatric disorders including depression and post-traumatic stress disorder. Aggressive experience, on the other hand, may promote disorders involving inappropriate aggression and violence. Current research using animal models of social conflict involves multiple levels of analysis from genetic and molecular to systems and overt behavior. This review briefly examines a variety of these animal models of social conflict in order to assess whether they are useful for advancing our understanding of how experience can shape brain and behavior and for translating this information so that we have the potential to improve the quality of life of individuals with mental illness and behavioral disorders.

The effect of childhood malnutrition on externalizing behavior

PURPOSE OF REVIEW

Childhood externalizing behavior (aggression, hyperactivity, and conduct disorder) has been increasingly viewed as a public health problem because of its etiology and outcome. The association between malnutrition and externalizing behavior has begun to receive attention. This review summarizes recent empirical findings on malnutrition as a risk factor for the development of externalizing behavior, with an emphasis on micronutrient deficiency, and explores brain dysfunction as a possible mechanism.

RECENT FINDINGS

Externalizing behavior is associated with both macromalnutrition (e.g. protein) and micromalnutrition (e.g. iron and zinc). Both prenatal and postnatal malnutrition is implicated. The long-term effects of malnutrition on behavior could be reversible. The effects of docosahexaenoic acid/omega-3 long-chain essential fatty acid on externalizing behavior are more mixed. From animal and human findings, it is hypothesized that malnutrition impairs neurocognitive functioning by reducing neurons, alternating neurotransmitter functioning, and increasing neurotoxicity, and that such neurocognitive impairments predispose to externalizing behavior.

SUMMARY

Different lines of evidence support the view that poor nutrition contributes to the development of child behavior problems. More randomized, controlled trials that manipulate nutritional intake and evaluate behavior in children are needed to evaluate the etiological role of nutrition in externalizing behavior in order to inform intervention and prevention efforts.