Developmental variation in amygdala volumes among children with posttraumatic stress

The Dynamic Interplay Between Puberty and Structural Brain Development as a Predictor of Mental Health Difficulties in Adolescence: A Systematic Review

Puberty is a time of intense reorganization of brain structure and a high-risk period for the onset of mental health problems, with variations in pubertal timing and tempo intensifying this risk. We conducted 2 systematic reviews of articles published up to February 1, 2024, focusing on 1) the role of brain structure in the relationship between puberty and mental health, and 2) precision psychiatry research evaluating the utility of puberty in making individualized predictions of mental health outcomes in young people. The first review provides inconsistent evidence about whether and how pubertal and psychopathological processes may interact in relation to brain development. While most studies found an association between early puberty and mental health difficulties in adolescents, evidence on whether brain structure mediates this relationship is mixed. The pituitary gland was found to be associated with mental health status during this time, possibly through its central role in regulating puberty and its function in the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axes. In the second review, the design of studies that have explored puberty in predictive models did not allow for a quantification of its predictive power. However, when puberty was evaluated through physically observable characteristics rather than hormonal measures, it was more commonly identified as a predictor of depression, anxiety, and suicidality in adolescence. Social processes may be more relevant than biological ones to the link between puberty and mental health problems and represent an important target for educational strategies.

A Functional Magnetic Resonance Imaging Meta-Analysis of Childhood Trauma

BACKGROUND

Traumatic experiences during childhood significantly impact the developing brain and contribute to the development of numerous physical and mental health problems. To date, however, a comprehensive understanding of the functional impairments within the brain associated with childhood trauma histories does not exist. Previous functional magnetic resonance imaging (fMRI) meta-analytical tools required homogeneity of task types and the clinical populations studied, thus preventing the comprehensive pooling of brain-based deficits present in children who have trauma histories. We hypothesized that the use of the novel, data-driven Bayesian author-topic model approach to fMRI meta-analyses would reveal deficits in brain networks that span fMRI task types in children with trauma histories.

METHODS

To our knowledge, this is the first study to use the Bayesian author-topic model approach to fMRI meta-analyses within a clinical population. Using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we present data-driven results obtained by combining activation patterns across heterogeneous tasks from 1428 initially screened studies and combining data from 14 studies that met study criteria (285 children with trauma histories, 297 healthy control children).

RESULTS

Altered brain activity was revealed within 2 clusters in children with trauma histories compared to control children: the default mode/affective network/posterior insula and the central executive network. Our identified clusters were associated with tasks pertaining to cognitive processing, emotional/social stress, self-referential thought, memory, unexpected stimuli, and avoidance behaviors in youths who have experienced childhood trauma.

CONCLUSIONS

Our results reveal disturbances in children with trauma histories within the modulation of the default mode and central executive networks-but not the salience network-regardless of whether children also presented with posttraumatic stress symptoms.

Gray matter differences in adults and children with posttraumatic stress disorder: A systematic review and meta-analysis of 113 studies and 11 meta-analyses

BACKGROUND

In this systematic review and meta-analysis, we aimed to provide a comprehensive overview of gray matter alterations of adult- and underage patients with posttraumatic stress disorder (PTSD) in comparison to healthy trauma-exposed (TC) and non-exposed (HC) individuals.

METHODS

We subdivided our groups into patients with PTSD after trauma exposure in adulthood (aa) or childhood (ac) as well as children with PTSD (cc). We identified 113 studies, including 6.800 participants in our review, which we divided into studies focusing on whole-brain and region-of-interest (ROI) analysis. We performed a coordinate-based meta-analysis on 14 studies in the group of aa-PTSD.

RESULTS

We and found lower gray matter volume in patients with PTSD (aa) in the medial frontal gyrus (PTSD<HC/TC) and Culmen/posterior cingulate cortex (PTSD<TC). Results from ROI-based studies mainly show alterations for patients with PTSD in the prefrontal cortex, hippocampus, anterior cingulate cortex, insula, corpus callosum, and amygdala.

LIMITATIONS

Due to a limited number of studies reporting whole-brain results, the meta-analyses could only be performed in one subgroup and within this subgroup for a limited number of studies.

CONCLUSIONS

Our results are in line with psychobiological models of PTSD that associate the identified regions with brain circuits involved in context processing, threat detection and emotion regulation.

Effects of social rank and pubertal delay on brain structure in female rhesus macaques

Adverse social experience during childhood and adolescence leads to developmental alterations in emotional and stress regulation and underlying neurocircuits. We examined the consequences of social subordination (low social rank) in juvenile female rhesus monkeys, as an ethologically valid model of chronic social stressor exposure, on brain structural and behavioral development through the pubertal transition. Adolescence is a developmental period of extensive brain remodeling and increased emotional and stress reactivity. Puberty-induced increases in gonadal hormones, particularly estradiol (E2), are likely involved due to its organizational effects on the brain and behavior. Thus, we also examined how experimentally delaying pubertal onset with Lupron (gonadotropin releasing hormone -GnRH- agonist used clinically to delay early puberty) interacted with social rank (dominant vs. subordinate) to affect brain and behavioral outcomes. Using a longitudinal experimental design, structural MRI (sMRI) scans were collected on socially housed juvenile female rhesus monkeys living in indoor-outdoor enclosures prior to the onset of puberty (18-25 months), defined as menarche or the initial occurrence of perineal swelling and coloration, and again at 29-36 months, when all control animals had reached puberty but none of the Lupron-treated had. We examined the effects of both social rank and pubertal delay on overall structural brain volume (i.e. intracranial, grey matter (GM) and white matter (WM) volumes), as well as on cortico-limbic regions involved in emotion and stress regulation: amygdala (AMYG), hippocampus (HC), and prefrontal cortex (PFC). Measures of stress physiology, social behavior, and emotional reactivity were collected to examine functional correlates of the brain structural effects. Apart from expected developmental effects, subordinates had bigger AMYG volumes than dominant animals, most notably in the right hemisphere, but pubertal delay with Lupron-treatment abolished those differences, suggesting a role of gonadal hormones potentiating the brain structural impact of social stress. Subordinates also had elevated baseline cortisol, indicating activation of stress systems. In general, Lupron-treated subjects had smaller AMYG and HC volume than controls, but larger total PFC (driven by bigger GM volumes), and different, region-specific, developmental patterns dependent on age and social rank. These findings highlight a region-specific effect of E2 on structural development during female adolescence, independent of those due to chronological age. Pubertal delay and AMYG volume, in turn, predicted differences in emotional reactivity and social behavior. These findings suggest that exposure to developmental increases in E2 modifies the consequences of adverse social experience on the volume of cortico-limbic regions involved in emotional and stress regulation during maturation. But, even more importantly, they indicate different brain structural effects of chronological age and pubertal developmental stage in females, which are very difficult to disentangle in human studies. These findings have additional relevance for young girls who experience prolonged pubertal delays or for those whose puberty is clinically arrested by pharmacological administration of Lupron.

Anxiety in children and youth with autism spectrum disorder and the association with amygdala subnuclei structure

Autism spectrum disorder (ASD) is clinically characterized by social and communication difficulties as well as repetitive behaviors. Many children with ASD also suffer from anxiety, which has been associated with alterations in amygdala structure. In this work, the association between amygdala subnuclei volumes and anxiety was assessed in a cohort of 234 participants (mean age = 11.0 years, SD = 3.9, 95 children with ASD, 139 children were non-autistic). Children underwent magnetic resonance imaging. Amygdala subnuclei volumes were extracted automatically. Anxiety was assessed using the Screen for Child Anxiety Related Disorders, the Child Behavior Checklist, and the Strength and Difficulties Questionnaire. Children with ASD had higher anxiety scores relative to non-autistic children on all anxiety measures (all, p < 0.05). Anxiety levels were significantly predicted in children with ASD by right basal (right: B = 0.235, p = 0.002) and paralaminar (PL) (B = −0.99, p = 0.009) volumes. Basal nuclei receive multisensory information from cortical and subcortical areas and have extensive projections within the limbic system while the PL nuclei are involved in emotional processing. Alterations in basal and PL nuclei in children with ASD and the association with anxiety may reflect morphological changes related to in the neurocircuitry of anxiety in ASD.

Lay abstract

Autism spectrum disorder (ASD) is clinically characterized by social communication difficulties as well as restricted and repetitive patterns of behavior. In addition, children with ASD are more likely to experience anxiety compared with their peers who do not have ASD. Recent studies suggest that atypical amygdala structure, a brain region involved in emotions, may be related to anxiety in children with ASD. However, the amygdala is a complex structure composed of heterogeneous subnuclei, and few studies to date have focused on how amygdala subnuclei relate to in anxiety in this population. The current sample consisted of 95 children with ASD and 139 non-autistic children, who underwent magnetic resonance imaging (MRI) and assessments for anxiety. The amygdala volumes were automatically segmented. Results indicated that children with ASD had elevated anxiety scores relative to peers without ASD. Larger basal volumes predicted greater anxiety in children with ASD, and this association was not seen in non-autistic children. Findings converge with previous literature suggesting ASD children suffer from higher levels of anxiety than non-autistic children, which may have important implications in treatment and interventions. Our results suggest that volumetric estimation of amygdala’s subregions in MRI may reveal specific anxiety-related associations in children with ASD.

Neural contributors to trauma resilience: a review of longitudinal neuroimaging studies

Resilience in the face of major life stressors is changeable over time and with experience. Accordingly, differing sets of neurobiological factors may contribute to an adaptive stress response before, during, and after the stressor. Longitudinal studies are therefore particularly effective in answering questions about the determinants of resilience. Here we provide an overview of the rapidly-growing body of longitudinal neuroimaging research on stress resilience. Despite lingering gaps and limitations, these studies are beginning to reveal individual differences in neural circuit structure and function that appear protective against the emergence of future psychopathology following a major life stressor. Here we outline a neural circuit model of resilience to trauma. Specifically, pre-trauma biomarkers of resilience show that an ability to modulate activity within threat and salience networks predicts fewer stress-related symptoms. In contrast, early post-trauma biomarkers of subsequent resilience or recovery show a more complex pattern, spanning a number of major circuits including attention and cognitive control networks as well as primary sensory cortices. This novel synthesis suggests stress resilience may be scaffolded by stable individual differences in the processing of threat cues, and further buttressed by post-trauma adaptations to the stressor that encompass multiple mechanisms and circuits. More attention and resources supporting this work will inform the targets and timing of mechanistic resilience-boosting interventions.

Developmental Variation in Amygdala Volumes: Modeling Differences Across Time, Age, and Puberty

BACKGROUND

There is evidence that the amygdala undergoes extensive development. The exact nature of this change remains less clear, with evidence suggesting linear, curvilinear, and null effects. The aim of this study was the identification of a normative reference of left and right amygdala development by parceling variance into separate effects of age and longitudinal growth.

METHODS

Data came from the National Institutes of Health MRI Study of Normal Brain Development. Participants in this sample were 54% female and ranged in age from 5 to 18 years (mean = 11.37 years) at study entry.

RESULTS

As predicted, the age at initial scan moderated the slope of both left and right amygdala volumes, demonstrating that the nature of longitudinal growth varies across age (i.e., steeper slopes observed among those first scanned at an early age). Follow-up analysis showed that the positive longitudinal growth slope becomes nonsignificant at 13.1 years of age for the left amygdala and at 14.5 years for the right amygdala, suggesting that growth of the left amygdala peaks earlier than growth of the right amygdala.

CONCLUSIONS

Findings suggest that rapid increases in volumes at early ages decline as youths enter adolescence and may turn to minor declines in volume during late adolescence or early adulthood.

Meta-analysis of Structural Magnetic Resonance Imaging Studies in Pediatric Posttraumatic Stress Disorder and Comparison With Related Conditions

BACKGROUND

Findings on structural brain volume associated with pediatric posttraumatic stress disorder (PTSD) have been variable, and it is unclear whether any structural differences are specific to pediatric PTSD in comparison with adult PTSD or other co-occurring pediatric psychiatric conditions.

METHODS

We tested volumetric brain differences between pediatric groups with and without PTSD in a region-of-interest meta-analysis. We conducted meta-regressions to test the effects of age and sex on heterogeneous study findings. To assess specificity, we compared pediatric PTSD with the following: adult PTSD, pediatric trauma exposure without PTSD, pediatric depression, and pediatric anxiety.

RESULTS

In 15 studies examined, pediatric PTSD was associated with smaller total gray matter and cerebral, temporal lobe (total, right, and left), total cerebellar vermis, and hippocampal (total, right, and left) volumes, compared to peers without PTSD. In the pediatric PTSD group, but not the comparison group, we found a trend toward smaller total, right, and left amygdalar volumes. In an external comparison, smaller hippocampal volume was not significantly different between adult and pediatric PTSD groups. Qualitative comparisons with a pediatric trauma exposure without PTSD group, a pediatric depression group, and a pediatric anxiety group revealed differences that may be unique to pediatric PTSD, and others that may be convergent with these related clinical conditions in youth.

CONCLUSIONS

Pediatric PTSD is associated with structural differences that parallel those associated with adult PTSD. Furthermore, pediatric PTSD appears to be distinct from other related pediatric conditions at the structural level. Future studies employing longitudinal, dimensional, and multimodal neuroimaging approaches will further elucidate the nature of neurobiological differences in pediatric PTSD.

Increased right amygdala metabolite concentrations in the absence of atrophy in children and adolescents with PTSD

Previous studies have shown that posttraumatic stress disorder (PTSD) is associated with dysfunction of the limbic system, in which the amygdala plays an important role. The purpose of this study was to evaluate whether the neurochemical concentrations assessed by proton magnetic resonance spectroscopy (¹H-MRS) in the amygdala are abnormal in children and adolescents with PTSD. Twenty-eight pediatric PTSD patients (11 boys, 17 girls) and 24 matched trauma-exposed control subjects (9 boys, 15 girls) underwent magnetic resonance brain imaging and ¹H-MRS of the bilateral amygdalae. The concentrations of N-acetylaspartate (NAA), myo-inositol (mI), total creatine (tCr) and total choline (tCho) in the right amygdala were significantly increased in PTSD patients compared with trauma-exposed control subjects. There were significant group-by-age interactions in the left amygdala NAA and right amygdala mI concentrations: older pediatric patients with PTSD had higher left amygdala NAA concentration and younger patients had higher right amygdala mI concentration than trauma-exposed control subjects. There was also a significant correlation between right mI concentration and time since trauma in PTSD patients. Finally, there was significant group-by-age interaction in the left amygdala volume; intragroup analysis revealed that the right amygdala volume was significantly lower than the left in the PTSD group, but not in the control group. These neurochemical abnormalities of the amygdala may indicate that dysfunctions of both neurons and glial cells are involved in the pathology of pediatric PTSD.

Annual Research Review: Pediatric posttraumatic stress disorder from a neurodevelopmental network perspective

BACKGROUND

Experiencing traumatic stress is common and may lead to posttraumatic stress disorder (PTSD) in a number of children and adolescents. Research using advanced imaging techniques is beginning to elucidate some of the neurobiological correlates of the traumatic stress response in youth.

METHODS

This paper summarizes the emerging network perspective of PTSD symptoms and reviews brain imaging research emphasizing structural and functional connectivity studies that employ magnetic resonance imaging techniques in pediatric samples.

RESULTS

Differences in structural connections and distributed functional networks such as the salience, default mode, and central executive networks are associated with traumatic and severe early life stress. The role of development has been relatively underappreciated in extant studies though there is evidence that critical brain regions as well as the structural and functional networks implicated undergo significant change in childhood and these typical developmental differences may be affected by traumatic stress.

CONCLUSIONS

Future research will benefit from adopting a truly developmental approach that considers children's growth as a meaningful effect (rather than simply a covariate) interacting with traumatic stress to predict disruptions in the anatomical, functional, and connective aspects of brain systems thought to underlie the network of PTSD symptoms. Linking symptom networks with neurodevelopmental network models may be a promising avenue for future work.

Ethical Issues in Conducting Research With Children and Families Affected by Disasters

PURPOSE OF REVIEW

We review topical evidence on ethical issues in conducting disaster research with children and families affected by natural disasters, with an emphasis on analyzing specific vulnerabilities associated with children and families affected by disasters, identifying significant findings and trends of ethical guidelines and approaches, and discussing key observations into ethical research in a disaster setting.

RECENT FINDINGS

Current evidence indicates that there is a wide range of research methods for child disaster studies. Vulnerability as a concept in child disaster studies is more prevalent with several scholars underscoring the need for an ethical approach to disaster research. Current disaster research evidence suggests that there is specifically an interest in conducting disaster research with children and families. With the increase in investigations, it is strongly recommended that investigators adhere to ethical standards in research practice when conducting research with vulnerable populations (e.g., children) within a postdisaster context.

Associations Between Trauma Type, Timing, and Accumulation on Current Coping Behaviors in Adolescents: Results from a Large, Population-based Sample

The development of adolescents' coping in response to stress is critical for adaptive functioning; these coping strategies may be shaped by numerous environmental factors during childhood, including experiences such as exposure to trauma. Childhood trauma has been shown to undermine contemporaneous coping, but how does a history of exposure to trauma and the characteristics of that trauma (type, timing, and accumulation) relate to current coping among adolescents? We addressed this question using a nationally-representative sample of 9427 adolescents (ages 13-18; 48.9% female; 66% White). Adolescents reported on their lifetime exposure to 18 different traumas, including witnessing or experiencing interpersonal violence, accidents, disasters, and violent or accidental loss of loved ones, as well as their current use of coping behaviors when under stress (problem-focused, positive emotion-focused, and negative emotion-focused coping strategies). The study's results highlight that exposure to nearly all forms of trauma was unrelated to problem-focused and positive emotion-focused coping behaviors, but strongly associated with increased negative emotion-focused coping. Use of each coping style did not vary with age at first exposure to trauma, but increased with the number of lifetime traumatic events experienced. The findings suggest that the extent of prior exposure to trauma, including variations across type and timing, may be related to a particular form of coping that has been linked to increased risk for mental health problems. Study results highlight coping strategies as a potential target for prevention and treatment efforts, and indicate a need to better understand the malleability and trajectory of coping responses to stress for promoting healthy youth development.

Does pediatric post-traumatic stress disorder alter the brain? Systematic review and meta-analysis of structural and functional magnetic resonance imaging studies

Several studies have recently demonstrated that the volumes of specific brain regions are reduced in children and adolescents with post-traumatic stress disorder (PTSD) compared with those of healthy controls. Our study investigated the potential association between early traumatic experiences and altered brain regions and functions. We conducted a systematic review of the scientific literature regarding functional magnetic resonance imaging and a meta-analysis of structural magnetic resonance imaging studies that investigated cerebral region volumes in pediatric patients with PTSD. We searched for articles from 2000 to 2014 in the PsycINFO, PubMed, Medline, Lilacs, and ISI (Web of Knowledge) databases. All data regarding the amygdala, hippocampus, corpus callosum, brain, and intracranial volumes that fit the inclusion criteria were extracted and combined in a meta-analysis that assessed differences between groups. The meta-analysis found reduced total corpus callosum areas and reduced total cerebral and intracranial volumes in the patients with PTSD. The total hippocampus (left and right hippocampus) and gray matter volumes of the amygdala and frontal lobe were also reduced, but these differences were not significant. The functional studies revealed differences in brain region activation in response to stimuli in the post-traumatic stress symptoms/PTSD group. Our results confirmed that the pediatric patients with PTSD exhibited structural and functional brain abnormalities and that some of the abnormalities occurred in different brain regions than those observed in adults.

Dissociable relations between amygdala subregional networks and psychopathy trait dimensions in conduct-disordered juvenile offenders

Psychopathy is a serious psychiatric phenomenon characterized by a pathological constellation of affective (e.g., callous, unemotional), interpersonal (e.g., manipulative, egocentric), and behavioral (e.g., impulsive, irresponsible) personality traits. Though amygdala subregional defects are suggested in psychopathy, the functionality and connectivity of different amygdala subnuclei is typically disregarded in neurocircuit-level analyses of psychopathic personality. Hence, little is known of how amygdala subregional networks may contribute to psychopathy and its underlying trait assemblies in severely antisocial people. We addressed this important issue by uniquely examining the intrinsic functional connectivity of basolateral (BLA) and centromedial (CMA) amygdala networks in relation to affective, interpersonal, and behavioral traits of psychopathy, in conduct-disordered juveniles with a history of serious delinquency (N = 50, mean age = 16.83 ± 1.32). As predicted, amygdalar connectivity profiles exhibited dissociable relations with different traits of psychopathy. Interpersonal psychopathic traits not only related to increased connectivity of BLA and CMA with a corticostriatal network formation accommodating reward processing, but also predicted stronger CMA connectivity with a network of cortical midline structures supporting sociocognitive processes. In contrast, affective psychopathic traits related to diminished CMA connectivity with a frontolimbic network serving salience processing and affective responding. Finally, behavioral psychopathic traits related to heightened BLA connectivity with a frontoparietal cluster implicated in regulatory executive functioning. We suggest that these trait-specific shifts in amygdalar connectivity could be particularly relevant to the psychopathic phenotype, as they may fuel a self-centered, emotionally cold, and behaviorally disinhibited profile. Hum Brain Mapp 37:4017-4033, 2016. © 2016 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Abnormal functional architecture of amygdala-centered networks in adolescent posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is a prevalent, debilitating, and difficult to treat psychiatric disorder. Very little is known of how PTSD affects neuroplasticity in the developing adolescent brain. Whereas multiple lines of research implicate amygdala-centered network dysfunction in the pathophysiology of adult PTSD, no study has yet examined the functional architecture of amygdala subregional networks in adolescent PTSD. Using intrinsic functional connectivity analysis, we investigated functional connectivity of the basolateral (BLA) and centromedial (CMA) amygdala in 19 sexually abused adolescents with PTSD relative to 23 matched controls. Additionally, we examined whether altered amygdala subregional connectivity coincides with abnormal grey matter volume of the amygdaloid complex. Our analysis revealed abnormal amygdalar connectivity and morphology in adolescent PTSD patients. More specifically, PTSD patients showed diminished right BLA connectivity with a cluster including dorsal and ventral portions of the anterior cingulate and medial prefrontal cortices (p < 0.05, corrected). In contrast, PTSD patients showed increased left CMA connectivity with a cluster including the orbitofrontal and subcallosal cortices (p < 0.05, corrected). Critically, these connectivity changes coincided with diminished grey matter volume within BLA and CMA subnuclei (p < 0.05, corrected), with CMA connectivity shifts additionally relating to more severe symptoms of PTSD. These findings provide unique insights into how perturbations in major amygdalar circuits could hamper fear regulation and drive excessive acquisition and expression of fear in PTSD. As such, they represent an important step toward characterizing the neurocircuitry of adolescent PTSD, thereby informing the development of reliable biomarkers and potential therapeutic targets.

Amygdalar volumetric correlates of social anxiety in offspring of parents with bipolar disorder

The prevalence of social anxiety disorder is high in offspring of parents with bipolar disorder (BD) and anxiety may be a significant risk factor in these youth for developing BD. We compared social anxiety symptoms between BD offspring with mood symptoms (high-risk group for developing BD I or II: HR) and healthy controls (HC). We also explored the correlations between the amygdalar volumes and social anxiety symptoms in the HR group with high social anxiety scores (HRHSA) due to the potential involvement of the amygdala in the pathophysiology of both BD and social anxiety. Youth participating in the study included 29h and 17HC of comparable age and gender. To assess social anxiety symptoms, we used the Multidimensional Anxiety Scale for Children (MASC) social anxiety subscale. The HR group's MASC social anxiety score was significantly higher than that of the HC group. Among the 29h, 17 subjects (58.6%) showed high social anxiety and they were classified as the HRHSA group. No significant difference was observed in amygdalar volume between the HRHSA and HC groups. However, there were significant negative correlations between amydalar volumes and MASC social anxiety score in the HRHSA group. These findings have implications for the link between amygdalar structure and both anxiety and mood control. This link may serve to implicate high social anxiety as a risk marker for future BD development.

Post-traumatic stress and age variation in amygdala volumes among youth exposed to trauma

Theoretically, normal developmental variation in amygdala volumes may be altered under conditions of severe stress. The purpose of this article was to examine whether posttraumatic stress moderates the association between age and amygdala volumes in youth exposed to traumatic events who are experiencing symptoms of post-traumatic stress disorder (PTSD). Volumetric imaging was conducted on two groups of youth aged 9-17 years: 28 with exposure to trauma and PTSD symptoms (boys = 15, girls = 13) and 26 matched (age, IQ) comparison youth (Controls; boys = 12, girls = 14). There was a significant group by age interaction in predicting right amygdala volumes. A positive association between age and right amygdala volumes was observed, but only in PTSD youth. These associations with age remained when controlling for IQ, total brain volumes and sex. Moreover, older youth with PTSD symptoms had relatively larger right amygdala volumes than controls. Findings provide evidence that severe stress may influence age-related variation in amygdala volumes. Results further highlight the importance of utilizing age as an interactive variable in pediatric neuroimaging research, in so far as age may act as an important moderator of group differences.