Nathaniel Harnett

• PhD
• McLean Hospital

Background: Identifying robust neural signatures of posttraumatic stress disorder (PTSD) symptoms is important to facilitate precision psychiatry and help in understanding and treatment of the disorder. Emergent research suggests structural covariance of early visual regions is associated with later PTSD development. However, large-scale analyses a...

Background: Childhood adversity is associated with susceptibility to posttraumatic stress disorder (PTSD) in adulthood. Both PTSD and adverse experiences in childhood are linked to disrupted white matter microstructure, yet the role of white matter as a potential neural mechanism connecting childhood adversity to PTSD remains unclear. The present s...

Background: Residential segregation is associated with differential exposure to air pollution. Hippocampus structure and function are highly susceptible to pollutants and associated with posttraumatic stress disorder (PTSD) development. Therefore, we investigated associations between residential segregation, air pollutants, hippocampal neurobiology...

Prior investigations of emotion processing's neural underpinnings rely on a priori models of brain response, obscuring detection of task-relevant neurobiological processes with complex temporal dynamics. To overcome this limitation, we applied unsupervised machine learning to functional magnetic resonance imaging data acquired during the emotional...

Importance Research on resilience after trauma has often focused on individual-level factors (eg, ability to cope with adversity) and overlooked influential neighborhood-level factors that may help mitigate the development of posttraumatic stress disorder (PTSD). Objective To investigate whether an interaction between residential greenspace and se...

Understanding biological pathways that mediate trauma‐related psychopathology is a major goal for traumatic stress studies. There is growing interest in studying differences in neural, physiological, and behavioral correlates of traumatic stress across demographic groups (e.g., sex/gender, race/ethnicity). However, challenges remain in how to appro...

Neuroimaging is a major tool that holds immense translational potential for understanding psychiatric disorder phenomenology and treatment. However, although epidemiological and social research highlights the many ways inequity and representativeness influences mental health, there is a lack of consideration of how such issues may impact neuroimagi...

The inequitable distribution of economic resources and exposure to adversity between racial groups contributes to mental health disparities within the United States. Consideration of the potential neurodevelopmental consequences, however, has been limited particularly for neurocircuitry known to regulate the emotional response to threat. Characteri...

Importance Racial discrimination increases the risk of adverse brain health outcomes, potentially via neuroplastic changes in emotion processing networks. The involvement of deep brain regions (brainstem and midbrain) in these responses is unknown. Potential associations of racial discrimination with alterations in deep brain functional connectivit...

Adolescent substance use is linked with negative future outcomes (e.g., depression, anxiety, substance use disorder). Given that the brain undergoes significant maturation during adolescence, this developmental period may represent a time of particular vulnerability to substance use. Neuroimaging research has largely focused on heavy or binge patte...

This study examines the association between brain dynamic functional network connectivity (dFNC) and current/future posttraumatic stress (PTS) symptom severity, and the impact of sex on this relationship. By analyzing 275 participants’ dFNC data obtained ~2 weeks after trauma exposure, we noted that brain dynamics of an inter-network brain state li...

Sexual trauma (ST) occurs with alarming frequency in the United States in the form of both childhood sexual abuse (CSA) and adulthood sexual assault (ASA). It is well established that the effects of ST are pervasive and that ST can be a risk factor for the development of several psychiatric disorders. However, the potential for distinct psychologic...

Background: Trauma is a risk factor for developing maladaptive alcohol use. Preclinical research has shown that stress alters the processing of midbrain and striatal reward and incentive signals. However, little research has been conducted on alterations in reward-related neurocircuitry post-trauma in humans. Neuroimaging markers may be particularl...

Prior research has shown that racial discrimination (RD) impacts activation in threat network regions, including the ventromedial prefrontal cortex (vmPFC) and middle occipital cortex during attention to threat-relevant stimuli. However, little is known about the biological mechanisms that may modulate these effects; inflammation may be a pathway l...

Importance Differences in neighborhood socioeconomic characteristics are important considerations in understanding differences in risk vs resilience in mental health. Neighborhood disadvantage is associated with alterations in the function and structure of threat neurocircuitry. Objective To investigate associations of neighborhood disadvantage wi...

Purpose of Review Community- and neighborhood-level factors are important, but understudied, influences on trauma-related disorders and their treatment. In this review, we describe how neighborhood factors are evaluated including through aggregate measures, geospatially derived indices, and individual assessments. Recent Findings Prior work sugges...

Resilience is a dynamic process of recovery after trauma, but in most studies it is conceptualized as the absence of specific psychopathology following trauma. Using the large emergency department AURORA study (n=1,865, 63% women), we took a longitudinal, dynamic and transdiagnostic approach to define a static resilience (r) factor, that could expl...

Alterations in brain function and structure are reported among individuals with substance use disorders (SUD). Prior work in this domain has focused on cortico-striatal circuits in the development and maintenance of SUD. In healthy populations, individual differences in behavior and cognition are reflected in variability across the collective set o...

Exposure to violence during childhood can lead to functional changes in brain regions that are important for emotion expression and regulation, which may increase susceptibility to internalizing disorders in adulthood. Specifically, childhood violence exposure can disrupt the functional connectivity among brain regions that include the prefrontal c...

Background: Psychological trauma exposure and posttraumatic stress disorder (PTSD) have been associated with advanced epigenetic age. However, whether epigenetic aging measured at the time of trauma predicts the subsequent development of PTSD outcomes is unknown. Moreover, the neural substrates underlying posttraumatic outcomes associated with epi...

Childhood trauma is a known risk factor for trauma and stress-related disorders in adulthood. However, limited research has investigated the impact of childhood trauma on brain structure linked to later posttraumatic dysfunction. We investigated the effect of childhood trauma on white matter microstructure after recent trauma and its relationship w...

Objective: Black Americans in the United States are disproportionately exposed to childhood adversity compared with White Americans. Such disparities may contribute to race-related differences in brain structures involved in regulating the emotional response to stress, such as the amygdala, hippocampus, and prefrontal cortex (PFC). The authors inv...

Considerable racial/ethnic disparities persist in exposure to life stressors and socioeconomic resources that can directly affect threat neurocircuitry, particularly the amygdala, that partially mediates susceptibility to adverse posttraumatic outcomes. Limited work to date, however, has investigated potential racial/ethnic variability in amygdala...

Background Prior sexual trauma (ST) is associated with greater risk for posttraumatic stress disorder after a subsequent traumatic event; however, the underlying neurobiological mechanisms remain opaque. We investigated longitudinal posttraumatic dysfunction and amygdala functional dynamics following admission to an emergency department for new pri...

Background: Suicide is a leading cause of death, and rates of attempted suicide have increased during the COVID-19 pandemic. The under-diagnosed psychiatric phenotype of dissociation is associated with elevated suicidal self-injury; however, it has largely been left out of attempts to predict and prevent suicide. Objective: We designed an artificia...

Background Anxiety sensitivity involves the fear of anxiety-related symptoms and can exacerbate both major depressive disorder and posttraumatic stress disorder (PTSD) symptoms. However, it is unclear if anxiety sensitivity plays a similar role in dissociative identity disorder (DID) where symptoms of depression and PTSD commonly co-occur. We exami...

Racial discrimination (RD) has been consistently linked to adverse brain health outcomes. These may be due in part to RD effects on neural networks involved with threat appraisal and regulation; RD has been linked to altered activity in the rostral anterior cingulate cortex (rACC) and structural decrements in the anterior cingulum bundle and hippoc...

Visual components of trauma memories are often vividly re-experienced by survivors with deleterious consequences for normal function. Neuroimaging research on trauma has primarily focused on threat-processing circuitry as core to trauma-related dysfunction. Conversely, limited attention has been given to visual circuitry which may be particularly r...

The prefrontal cortex (PFC), hippocampus, and amygdala play an important role in emotional health. However, adverse life events (e.g., violence exposure) affect the function of these brain regions, which may lead to disorders such as depression and anxiety. Depression and anxiety disproportionately affect women compared to men, and this disparity m...

Black women in the United States (U.S.) are faced with unrelenting chronic stressors that are often driven by racism and oppression to influence mental health inequities. Similar to common U.S. societal views of Black women, ideological values about Black women’s lives also permeate psychiatry and neuroscience research to prevent likely impactful r...

Hippocampal impairments are reliably associated with post-traumatic stress disorder (PTSD); however, little research has characterized how increased threat-sensitivity may interact with arousal responses to alter hippocampal reactivity, and further how these interactions relate to the sequelae of trauma-related symptoms. In a sample of individuals...

Health is not merely the absence of disease or infirmity. Instead, it is a state of complete physical, mental, and social well-being (World Health Organization, 2020). As such, studying mental health requires broad, interdisciplinary approaches that will help better understand how the brain, body, and environment interact in maintaining mental heal...

Objective: Dissociation, a disruption or discontinuity in psychological functioning, is often linked with worse psychiatric symptoms; however, the prognostic value of dissociation after trauma is inconsistent. Determining whether trauma-related dissociation is uniquely predictive of later outcomes would enable early identification of at-risk traum...

Neuropsychiatry is beginning to reevaluate current research approaches in the wake of contemporary events of racialized violence against Black and other minoritized individuals. Although researchers, clinicians, and leaders have proposed reactionary personal and institutional commitments for change, many have done so without thoughtful consideratio...

Background Racial and ethnic groups in the USA differ in the prevalence of posttraumatic stress disorder (PTSD). Recent research however has not observed consistent racial/ethnic differences in posttraumatic stress in the early aftermath of trauma, suggesting that such differences in chronic PTSD rates may be related to differences in recovery over...

Objective: Major negative life events, such as trauma exposure, can play a key role in igniting or exacerbating psychopathology. However, few disorders are diagnosed with respect to precipitating events, and the role of these events in the unfolding of new psychopathology is not well understood. The authors conducted a multisite transdiagnostic lo...

Suicidal ideation and attempts (i.e., suicidality) are complex behaviors driven by environmental stress, genetic susceptibility, and their interaction. Preadolescent suicidality is a major health problem with rising rates, yet its underlying biology is understudied. Here we studied effects of genetic stress susceptibility, approximated by the polyg...

Posttraumatic stress disorder (PTSD) is associated with lower gray matter volume (GMV) in brain regions critical for extinction of learned threat. However, relationships among volume, extinction learning, and PTSD symptom development remain unclear. We investigated subcortical brain volumes in regions supporting extinction learning and fear-potenti...

Background: Stress-related disruption of emotion regulation appears to involve the prefrontal cortex (PFC) and amygdala. However, the interactions between brain regions that mediate stress-induced changes in emotion regulation remain unclear. The present study builds upon prior work that assessed stress-induced changes in the neurobehavioral respo...

Background Experiences of racial discrimination are linked to a range of negative brain health outcomes, but little is known about how these experiences impact neural architecture, including white matter microstructure, which may partially mediate these outcomes. Our goal was to examine associations between racially discriminatory experiences and w...

Importance Racial discrimination has a clear impact on health-related outcomes, but little is known about how discriminatory experiences are associated with neural response patterns to emotionally salient cues, which likely mediates these outcomes. Objective To examine associations of discriminatory experiences with brainwide response to threat-re...

This is the initial report of results from the AURORA multisite longitudinal study of adverse post-traumatic neuropsychiatric sequelae (APNS) among participants seeking emergency department (ED) treatment in the aftermath of a traumatic life experience. We focus on n = 666 participants presenting to EDs following a motor vehicle collision (MVC) and...

Suicidal ideation and attempts (i.e., suicidality) are complex behaviors driven by environmental stress, genetic susceptibility, and their interaction. Preadolescent suicidality is a major health problem with rising rates, yet its underlying biology is understudied. Here we studied effects of genetic stress susceptibility, estimated by polygenic ri...

Neighborhood disadvantage and community violence are common in poor, urban communities and are risk factors for emotional dysfunction. Emotional processes are supported by neural circuitry that includes the prefrontal cortex, hippocampus, amygdala, and hypothalamus. These brain regions are connected by white matter pathways that include the cingulu...

Prior studies highlight how threat-related arousal may impair hippocampal function. Hippocampal impairments are reliably associated with post-traumatic stress disorder (PTSD); however, little research has characterized how increased threat-sensitivity may drive arousal responses to alter hippocampal reactivity, and further how these alterations rel...

The prefrontal cortex and limbic system are important components of the neural circuit that underlies stress and anxiety. These brain regions are connected by white matter tracts that support neural communication including the cingulum, uncinate fasciculus, and the fornix/stria-terminalis. Determining the relationship between stress reactivity and...

The hippocampus and amygdala play an important role in the pathophysiology of posttraumatic stress disorder (PTSD). In fact, chronic PTSD has been consistently linked to reductions in hippocampal and amygdala volume. However, the acute impact posttraumatic stress has on the volume of these brain regions has received limited attention. Determining t...

Objective Childhood physical and sexual abuse are stressful experiences that may alter the emotional response to future stressors. Stress-related emotional function is supported by brain regions that include the prefrontal cortex (PFC), hippocampus, and amygdala. The present study investigated whether childhood physical and sexual abuse are associa...

Neurobiological markers of future susceptibility to posttraumatic stress disorder (PTSD) may facilitate identification of vulnerable individuals in the early aftermath of trauma. Variability in resting-state networks (RSNs), patterns of intrinsic functional connectivity across the brain, has previously been linked to PTSD, and may thus be informati...

Background: Anhedonic symptoms of posttraumatic stress disorder (PTSD) reflect deficits in reward processing that have significant functional consequences. Although recent evidence suggests that disrupted integrity of fronto‐limbic circuitry is related to PTSD development, including anhedonic PTSD symptoms (posttrauma anhedonia [PTA]), little is kn...

Chronic childhood stress is linked to greater susceptibility to internalizing disorders in adulthood. Specifically, chronic stress leads to changes in brain connectivity patterns, and, in turn, affects psychological functioning. Violence exposure, a chronic stressor, increases stress reactivity and disrupts emotion regulation processes. However, it...

The prefrontal cortex, amygdala, hippocampus, and hypothalamus are important components of the neural network that mediates the healthy learning, expression, and regulation of emotion. These brain regions are connected by white matter pathways that include the cingulum bundle, uncinate fasciculus, and fornix/stria terminalis. Individuals with traum...

Background Although aspects of brain morphology have been associated with chronic posttraumatic stress disorder (PTSD), limited work has investigated multimodal patterns in brain morphology that are linked to acute posttraumatic stress severity. In the present study, we utilized multimodal magnetic resonance imaging (MRI) to investigate if structur...

Although approximately 90% of the U.S. population will experience a traumatic event within their lifetime, only a fraction of those traumatized individuals will develop posttraumatic stress disorder (PTSD). In fact, approximately 7 out of 100 people in the U.S. will be afflicted by this debilitating condition, which suggests there is substantial in...

Decades of research into the biological mechanisms of PTSD suggests that chronic activation of the stress response leads to long-lasting changes in the structure and function of the nervous and endocrine systems. While the prevalence of PTSD is twice as high in females as males, little is known about how sex differences in neuroendocrine systems ma...

Threat-related emotional function is supported by a neural circuit that includes the prefrontal cortex (PFC), hippocampus, and amygdala. The function of this neural circuit is altered by negative life experiences, which can potentially affect threat-related emotional processes. Notably, Black-American individuals disproportionately endure negative...

Stress elicits a variety of psychophysiological responses that show large interindividual variability. Determining the neural mechanisms that mediate individual differences in the emotional response to stress would provide new insight that would have important implications for understanding stress-related disorders. Therefore, the present study exa...

Cognitive and emotional functions are supported by the coordinated activity of a distributed network of brain regions. This coordinated activity may be disrupted by psychosocial stress, resulting in the dysfunction of cognitive and emotional processes. Graph theory is a mathematical approach to assess coordinated brain activity that can estimate th...

Posttraumatic stress disorder (PTSD) is associated with dysfunction of the neural circuitry that supports fear learning and memory processes. However, much of what is known about neural dysfunction in PTSD is based on research in chronic PTSD populations. Less is known about neural function that supports fear learning acutely following trauma expos...

Stress tasks performed during functional magnetic resonance imaging (fMRI) elicit a relatively small cortisol response compared to stress tasks completed in a traditional behavioral laboratory, which may be due to apprehension of fMRI that elicits an anticipatory stress response. The present study investigated whether anticipatory stress is greater...

An important function of emotion is that it motivates us to respond more effectively to threats in our environment. Accordingly, healthy emotional function depends on the ability to appropriately avoid, escape, or defend against threats we encounter. Thus, from a functional perspective, it is important to understand the emotional response to threat...