Social fear extinction susceptibility is associated with Microbiota-Gut-Brain axis alterations.

Social anxiety disorder is a common psychiatric condition that severely affects quality of life of individuals and is a significant societal burden. Although many risk factors for social anxiety exist, it is currently unknown how social fear sensitivity manifests biologically. Furthermore, since some individuals are resilient and others are susceptible to social fear, it is important to interrogate the mechanisms underpinning individual response to social fear situations. The microbiota-gut-brain axis has been associated with social behaviour, has recently been linked with social anxiety disorder, and may serve as a therapeutic target for modulation. Here, we assess the potential of this axis to be linked with social fear extinction processes in a murine model of social anxiety disorder. To this end, we correlated differential social fear responses with microbiota composition, central gene expression, and immune responses. Our data provide evidence that microbiota variability is strongly correlated with alterations in social fear behaviour. Moreover, we identified altered gene candidates by amygdalar transcriptomics that are linked with social fear sensitivity. These include genes associated with social behaviour (Armcx1, Fam69b, Kcnj9, Maoa, Serinc5, Slc6a17, Spata2, and Syngr1), inflammation and immunity (Cars, Ckmt1, Klf5, Maoa, Map3k12, Pex5, Serinc5, Sidt1, Spata2), and microbe-host interaction (Klf5, Map3k12, Serinc5, Sidt1). Together, these data provide further evidence for a role of the microbiota-gut-brain axis in social fear responses.

Hyperglycemia and cognitive impairments anticipate the onset of an overt type 2 diabetes-like phenotype in TALLYHO/JngJ mice.

Type 2 Diabetes mellitus (T2DM) is a metabolic disorder characterized by chronic hyperglycemia, resulting from deficits in insulin secretion, insulin action, or both. Whilst the role of insulin in the peripheral nervous system has been ascertained in countless studies, its role in the central nervous system (CNS) is emerging only recently. Brain insulin has been lately associated with brain disorders like Alzheimer's disease, obsessive compulsive disorder, and attention deficit hyperactivity disorder. Thus, understanding the role of insulin as a common risk factor for mental and somatic comorbidities may disclose novel preventative and therapeutic approaches. We evaluated general metabolism (glucose tolerance, insulin sensitivity, energy expenditure, lipid metabolism, and polydipsia) and cognitive capabilities (attention, cognitive flexibility, and memory), in adolescent, young adult, and adult male and female TALLYHO/JngJ mice (TH, previously reported to constitute a valid experimental model of T2DM due to impaired insulin signaling). Adult TH mice have also been studied for alterations in gut microbiota diversity and composition. While TH mice exhibited profound deficits in cognitive flexibility and altered glucose metabolism, we observed that these alterations emerged either much earlier (males) or independent of (females) a comprehensive constellation of symptoms, isomorphic to an overt T2DM-like phenotype (insulin resistance, polydipsia, higher energy expenditure, and altered lipid metabolism). We also observed significant sex-dependent alterations in gut microbiota alpha diversity and taxonomy in adult TH mice. Deficits in insulin signaling may represent a common risk factor for both T2DM and CNS-related deficits, which may stem from (partly) independent mechanisms.

Sex- and cycle-dependent changes in spine density and size in hippocampal CA2 neurons.

Sex hormones affect structural and functional plasticity in the rodent hippocampus. However, hormone levels not only differ between males and females, but also fluctuate across the female estrous cycle. While sex- and cycle-dependent differences in dendritic spine density and morphology have been found in the rodent CA1 region, but not in the CA3 or the dentate gyrus, comparable structural data on CA2, i.e. the hippocampal region involved in social recognition memory, is so far lacking. In this study, we, therefore, used wildtype male and female mice in diestrus or proestrus to analyze spines on dendritic segments from identified CA2 neurons. In basal stratum oriens, we found no differences in spine density, but a significant shift towards larger spine head areas in male mice compared to females. Conversely, in apical stratum radiatum diestrus females had a significantly higher spine density, and females in either cycle stage had a significant shift towards larger spine head areas as compared to males, with diestrus females showing the larger shift. Our results provide further evidence for the sexual dimorphism of hippocampal area CA2, and underscore the importance of considering not only the sex, but also the stage of the estrous cycle when interpreting morphological data.

Insights from animal models on insulin signalling disturbances and related diseases in neurological and mental conditions.

There has been a growing awareness of the need for scientific research to focus on somatic and mental comorbidities in recent years due to the emerging evidence showing their substantial overlap at numerous levels. In this special issue, initiated by members of the EU-funded PRIME consortium ("Prevention and Remediation of Insulin Multimorbidity in Europe; www.prime-study.eu), the focus is on the comorbidities of metabolic disturbances, especially related to insulin signalling dysregulation and mental and neurological disorders. Thus, while obesity, type 2 diabetes, and metabolic syndrome are commonly known to be insulin-related disorders, the last decades have shown that neurodegenerative disorders, such as Alzheimer's disease, as well as neurodevelopment disorders, such as obsessive-compulsive disorder (OCD), autism spectrum disorders (ASDs) and attention deficit / hyperactivity disorder (ADHD) also fall into this category. The special issue draws together a series of basic and clinical review articles that describe the current knowledge and future perspectives regarding insulin comorbidities across a multidisciplinary group of experts.

Social anxiety disorder-associated gut microbiota increases social fear.

Social anxiety disorder (SAD) is a crippling psychiatric disorder characterized by intense fear or anxiety in social situations and their avoidance. However, the underlying biology of SAD is unclear and better treatments are needed. Recently, the gut microbiota has emerged as a key regulator of both brain and behaviour, especially those related to social function. Moreover, increasing data supports a role for immune function and oxytocin signalling in social responses. To investigate whether the gut microbiota plays a causal role in modulating behaviours relevant to SAD, we transplanted the microbiota from SAD patients, which was identified by 16S rRNA sequencing to be of a differential composition compared to healthy controls, to mice. Although the mice that received the SAD microbiota had normal behaviours across a battery of tests designed to assess depression and general anxiety-like behaviours, they had a specific heightened sensitivity to social fear, a model of SAD. This distinct heightened social fear response was coupled with changes in central and peripheral immune function and oxytocin expression in the bed nucleus of the stria terminalis. This work demonstrates an interkingdom basis for social fear responses and posits the microbiome as a potential therapeutic target for SAD.

A systematic review of preclinical studies exploring the role of insulin signalling in executive function and memory.

Beside its involvement in somatic dysfunctions, altered insulin signalling constitutes a risk factor for the development of mental disorders like Alzheimer's disease and obsessive-compulsive disorder. While insulin-related somatic and mental disorders are often comorbid, the fundamental mechanisms underlying this association are still elusive. Studies conducted in rodent models appear well suited to help decipher these mechanisms. Specifically, these models are apt to prospective studies in which causative mechanisms can be manipulated via multiple tools (e.g., genetically engineered models and environmental interventions), and experimentally dissociated to control for potential confounding factors. Here, we provide a narrative synthesis of preclinical studies investigating the association between hyperglycaemia - as a proxy of insulin-related metabolic dysfunctions - and impairments in working and spatial memory, and attention. Ultimately, this review will advance our knowledge on the role of glucose metabolism in the comorbidity between somatic and mental illnesses.

The modulation of platelet function by growth hormone in growth hormone deficient Hypopituitary patients.

BACKGROUND: Growth hormone deficiency (GHD) has been implicated in increased cardiovascular and cerebrovascular disease risk seen in hypopituitarism, however the mechanism remains speculative. We hypothesise that platelet abnormalities may play a contributory role. Herein we examined platelet behaviour in GHD hypopituitary patients, pre- and post-growth hormone (GH) replacement. METHODS: This study utilizes a physiological flow-based assay to quantify platelet function in whole blood from patient cohorts under arterial shear. Thirteen GH Naïve hypopituitary adults with GHD and thirteen healthy matched controls were studied. Patients were assessed before and after GH treatment. All other pituitary replacements were optimised before the study. In addition to a full endocrine profile, whole blood was labelled and perfused over immobilised von Willibrand factor (vWF). Seven parameters of dynamic platelet-vWF interactions were recorded using digital image microscopy and analysed by customised platelet tracking software. RESULTS: We found a significantly altered profile of platelet-vWF interactions in GHD individuals compared to healthy controls. Specifically, we observed a marked increase in platelets shown to form associations such as tethering, rolling and adherence to immobilized vWF, which were reduced post GH treatment. Speed and distance platelets travelled across vWF was similar between controls and pre-therapy GHD patients, however, this was considerably increased post treatment. This may indicate reduced platelet signaling resulting in less stable adhesion of platelets post GH treatment. CONCLUSIONS: Taken together observed differences in platelet behaviour may contribute to an increased risk of thrombosis in GHD which can in part be reversed by GH therapy.

Embryonic and adult synaptic proteome perturbations after maternal immune activation: Identification of persistent changes relevant for early intervention.

Maternal infections during pregnancy pose an increased risk for neurodevelopmental psychiatric disorders (NPDs) in the offspring. Here, we examined age- and sex-dependent dynamic changes of the hippocampal synaptic proteome after maternal immune activation (MIA) in embryonic and adult mice. Adult male and female MIA offspring exhibited social deficits and sex-specific depression-like behaviours, among others, validating the model. Furthermore, we observed dose-, age-, and sex-dependent synaptic proteome differences. Analysis of the embryonic synaptic proteome implicates sphingolipid and ketoacid metabolism pathway disruptions during neurodevelopment for NPD-pertinent sequelae. In the embryonic hippocampus, prenatal immune activation also led to changes in neuronal guidance, glycosphingolipid metabolism important for signalling and myelination, and post-translational modification of proteins that regulate intercellular interaction and developmental timing. In adulthood, the observed changes in synaptoneurosomes revealed a dynamic shift toward transmembrane trafficking, intracellular signalling cascades, and hormone-mediated metabolism. Importantly, 68 of the proteins with differential abundance in the embryonic brains of MIA offspring were also altered in adulthood, 75% of which retained their directionality. These proteins are involved in synaptic organisation, neurotransmitter receptor regulation, and the vesicle cycle. A cluster of persistently upregulated proteins, including AKT3, PAK1/3, PPP3CA, formed a functional network enriched in the embryonic brain that is involved in cellular responses to environmental stimuli. To infer a link between the overlapping protein alterations and cognitive and psychiatric traits, we probed human phenome-wise association study data for cognitive and psychiatric phenotypes and all, but PORCN were significantly associated with the investigated domains. Our data provide insights into the dynamic effects of an early prenatal immune activation on developing and mature hippocampi and highlights targets for early intervention in individuals exposed to such immune challenges.

Nonfatal Injuries Sustained in Mass Shootings in the US, 2012-2019: Injury Diagnosis Matrix, Incident Context, and Public Health Considerations.

INTRODUCTION: The epidemic of gun violence in the United States (US) is exacerbated by frequent mass shootings. In 2021, there were 698 mass shootings in the US, resulting in 705 deaths and 2,830 injuries. This is a companion paper to a publication in JAMA Network Open, in which the nonfatal outcomes of victims of mass shootings have been only partially described. METHODS: We gathered clinical and logistic information from 31 hospitals in the US about 403 survivors of 13 mass shootings, each event involving greater than 10 injuries, from 2012-19. Local champions in emergency medicine and trauma surgery provided clinical data from electronic health records within 24 hours of a mass shooting. We organized descriptive statistics of individual-level diagnoses recorded in medical records using International Classification of Diseases codes, according to the Barell Injury Diagnosis Matrix (BIDM), a standardized tool that classifies 12 types of injuries within 36 body regions. RESULTS: Of the 403 patients who were evaluated at a hospital, 364 sustained physical injuries-252 by gunshot wound (GSW) and 112 by non-ballistic trauma-and 39 were uninjured. Fifty patients had 75 psychiatric diagnoses. Nearly 10% of victims came to the hospital for symptoms triggered by, but not directly related to, the shooting, or for exacerbations of underlying conditions. There were 362 gunshot wounds recorded in the Barell Matrix (1.44 per patient). The Emergency Severity Index (ESI) distribution was skewed toward higher acuity than typical for an emergency department (ED), with 15.1% ESI 1 and 17.6% ESI 2 patients. Semi-automatic firearms were used in 100% of these civilian public mass shootings, with 50 total weapons for 13 shootings (Route 91 Harvest Festival, Las Vegas. 24). Assailant motivations were reported to be associated with hate crimes in 23.1%. CONCLUSION: Survivors of mass shootings have substantial morbidity and characteristic injury distribution, but 37% of victims had no GSW. Law enforcement, emergency medical systems, and hospital and ED disaster planners can use this information for injury mitigation and public policy planning. The BIDM is useful to organize data regarding gun violence injuries. We call for additional research funding to prevent and mitigate interpersonal firearm injuries, and for the National Violent Death Reporting System to expand tracking of injuries, their sequelae, complications, and societal costs.

Selective breeding of rats for high (HAB) and low (LAB) anxiety-related behaviour: A unique model for comorbid depression and social dysfunctions.

Animal models of selective breeding for extremes in emotionality are a strong experimental approach to model psychopathologies. They became indispensable in order to increase our understanding of neurobiological, genetic, epigenetic, hormonal, and environmental mechanisms contributing to anxiety disorders and their association with depressive symptoms or social deficits. In the present review, we extensively discuss Wistar rats selectively bred for high (HAB) and low (LAB) anxiety-related behaviour on the elevated plus-maze. After 30 years of breeding, we can confirm the prominent differences between HAB and LAB rats in trait anxiety, which are accompanied by consistent differences in depressive-like, social and cognitive behaviours. We can further confirm a single nucleotide polymorphism in the vasopressin promotor of HAB rats causative for neuropeptide overexpression, and show that low (or high) anxiety and fear levels are unlikely due to visual dysfunctions. Thus, HAB and LAB rats continue to exist as a reliable tool to study the multiple facets underlying the pathology of high trait anxiety and its comorbidity with depression-like behaviour and social dysfunctions.

Impact of insulin and insulin resistance on brain dopamine signalling and reward processing - An underexplored mechanism in the pathophysiology of depression?

Type 2 diabetes and major depressive disorder (MDD) are the leading causes of disability worldwide and have a high comorbidity rate with fatal outcomes. Despite the long-established association between these conditions, the underlying molecular mechanisms remain unknown. Since the discovery of insulin receptors in the brain and the brain's reward system, evidence has accumulated indicating that insulin modulates dopaminergic (DA) signalling and reward behaviour. Here, we review the evidence from rodent and human studies, that insulin resistance directly alters central DA pathways, which may result in motivational deficits and depressive symptoms. Specifically, we first elaborate on the differential effects of insulin on DA signalling in the ventral tegmental area (VTA) - the primary DA source region in the midbrain - and the striatum as well as its effects on behaviour. We then focus on the alterations induced by insulin deficiency and resistance. Finally, we review the impact of insulin resistance in DA pathways in promoting depressive symptoms and anhedonia on a molecular and epidemiological level and discuss its relevance for stratified treatment strategies.

Insulin and disorders of behavioural flexibility.

Behavioural inflexibility is a symptom of neuropsychiatric and neurodegenerative disorders such as Obsessive-Compulsive Disorder, Autism Spectrum Disorder and Alzheimer's Disease, encompassing the maintenance of a behaviour even when no longer appropriate. Recent evidence suggests that insulin signalling has roles apart from its regulation of peripheral metabolism and mediates behaviourally-relevant central nervous system (CNS) functions including behavioural flexibility. Indeed, insulin resistance is reported to generate anxious, perseverative phenotypes in animal models, with the Type 2 diabetes medication metformin proving to be beneficial for disorders including Alzheimer's Disease. Structural and functional neuroimaging studies of Type 2 diabetes patients have highlighted aberrant connectivity in regions governing salience detection, attention, inhibition and memory. As currently available therapeutic strategies feature high rates of resistance, there is an urgent need to better understand the complex aetiology of behaviour and develop improved therapeutics. In this review, we explore the circuitry underlying behavioural flexibility, changes in Type 2 diabetes, the role of insulin in CNS outcomes and mechanisms of insulin involvement across disorders of behavioural inflexibility.

Phase-and disorder-specific differences in peripheral metabolites of the kynurenine pathway in major depression, bipolar affective disorder and schizophrenia.

OBJECTIVES: Kynurenine, kynurenic and quinolinic acid are important metabolites in tryptophan metabolism. Due to an involvement in glutamatergic neurotransmission and immune response, previous studies have investigated this pathway in mental disorders such as major depressive disorder (MDD), bipolar disorder (BD) or schizophrenia (SCZ). Tryptophan and kynurenine have been shown to be decreased across disorders, hinting at the missing link how inflammation causes neurotoxicity and psychiatric symptoms. The main aim of our study was to investigate if individual catabolites could serve as diagnostic biomarkers for MDD, BD and SCZ. METHODS: We measured plasma levels of tryptophan, kynurenine, kynurenic acid, quinolinic acid and ratio of quinolinic acid/kynurenic acid using mass spectrometry in n = 175 participants with acute episodes and after remission, compared with controls. RESULTS: Decreased levels of all tryptophan catabolites were found in the whole patient group, driven by the difference between BD and HC. Manic and mixed phase BD individuals displayed significantly lower kynurenine and kynurenic acid levels. We could not find significant differences between disorders. Upon reaching remission, changes in catabolite levels partially normalised. CONCLUSIONS: Our data suggests an involvement of the kynurenine pathway in mental disorders, especially BD but disqualifying those metabolites as biomarkers for differential diagnosis.

Mass Shootings in America: Consensus Recommendations for Healthcare Response.

BACKGROUND: In 2021, 702 people died in mass shooting incidents (MSIs) in the US. To define the best healthcare response to MSIs, the Uniformed Services University's National Center for Disaster Medicine and Public Health hosted a consensus conference of emergency medical services (EMS) clinicians, emergency medicine (EM) physicians, and surgeons who provided medical response to six of the nation's largest recent mass shootings. STUDY DESIGN: The study consisted of a 3-round modified Delphi process. A planning committee selected 6 MSI sites with the following criteria: the MSI occurred in 2016 or later, and must have resulted in at least 15 people killed and injured. The MSI sites were Orlando, FL, Las Vegas, NV, Sutherland Springs, TX, Parkland, FL, El Paso, TX, and Dayton, OH. Fifteen clinicians participated in the conference. All participants had EMS, EM, or surgery expertise and responded to 1 of the 6 MSIs. The first round consisted of a 2-part survey. The second and third rounds consisted of site-specific presentations followed by specialty-specific discussion groups to generate consensus recommendations. RESULTS: The 3 specialty-specific groups created 8 consensus recommendations in common. These 8 recommendations addressed readiness training, public education, triage, communication, patient tracking, medical records, family reunification, and mental health services for responders. There were an additional 11 recommendations created in common between 2 subgroups, either EMS and EM (2), EM and surgery (7), or EMS and surgery (2). CONCLUSIONS: There are multiple common recommendations identified by EMS, EM, and surgery clinicians who responded to recent MSIs. Clinicians, emergency planners, and others involved in preparing and executing a response to a future mass shooting event may benefit from considering these consensus lessons learned.

Disrupting the nNOS/NOS1AP interaction in the medial prefrontal cortex impairs social recognition and spatial working memory in mice.

The neuronal isoform of nitric oxide synthase (nNOS) and its interacting protein NOS1AP have been linked to several mental disorders including schizophrenia and depression. An increase in the interaction between nNOS and NOS1AP in the frontal cortex has been suggested to contribute to the emergence of these disorders. Here we aimed to uncover whether disruption of their interactions in the frontal cortex leads to mental disorder endophenotypes. Targeting the medial prefrontal cortex (mPFC), we stereotaxically injected wild-type C57BL/6J mice with recombinant adeno-associated virus (rAAV) expressing either full-length NOS1AP, the nNOS binding region of NOS1AP (i.e. NOS1AP396-503), or the nNOS amino-terminus (i.e. nNOS1-133), which was shown to disrupt the interaction of endogenous nNOS with PSD-95. We tested these mice in a comprehensive behavioural battery, assessing different endophenotypes related to mental disorders. We found no differences in anxiety-related and exploratory behaviours. Likewise, social interaction was comparable in all groups. However, social recognition was impaired in NOS1AP and NOS1AP396-503 mice. These mice, as well as mice overexpressing nNOS1-133 also displayed impaired spatial working memory (SWM) capacity, while spatial reference memory (SRM) remained intact. Finally, mice overexpressing NOS1AP and nNOS1-133, but not NOS1AP396-503, failed to habituate to the startling pulses in an acoustic startle response (ASR) paradigm, though we found no difference in overall startle intensity or prepulse inhibition (PPI) of the ASR. Our findings indicate a distinct role of NOS1AP/nNOS/PSD-95 interactions in the mPFC to contribute to specific endophenotypic changes observed in different mental disorders.

The translational genetics of ADHD and related phenotypes in model organisms.

Attention-deficit/hyperactivity disorder (ADHD) is a highly prevalent neurodevelopmental disorder resulting from the interaction between genetic and environmental risk factors. It is well known that ADHD co-occurs frequently with other psychiatric disorders due, in part, to shared genetics factors. Although many studies have contributed to delineate the genetic landscape of psychiatric disorders, their specific molecular underpinnings are still not fully understood. The use of animal models can help us to understand the role of specific genes and environmental stimuli-induced epigenetic modifications in the pathogenesis of ADHD and its comorbidities. The aim of this review is to provide an overview on the functional work performed in rodents, zebrafish and fruit fly and highlight the generated insights into the biology of ADHD, with a special focus on genetics and epigenetics. We also describe the behavioral tests that are available to study ADHD-relevant phenotypes and comorbid traits in these models. Furthermore, we have searched for new models to study ADHD and its comorbidities, which can be useful to test potential pharmacological treatments.

Behavioural and functional evidence revealing the role of RBFOX1 variation in multiple psychiatric disorders and traits.

Common variation in the gene encoding the neuron-specific RNA splicing factor RNA Binding Fox-1 Homolog 1 (RBFOX1) has been identified as a risk factor for several psychiatric conditions, and rare genetic variants have been found causal for autism spectrum disorder (ASD). Here, we explored the genetic landscape of RBFOX1 more deeply, integrating evidence from existing and new human studies as well as studies in Rbfox1 knockout mice. Mining existing data from large-scale studies of human common genetic variants, we confirmed gene-based and genome-wide association of RBFOX1 with risk tolerance, major depressive disorder and schizophrenia. Data on six mental disorders revealed copy number losses and gains to be more frequent in ASD cases than in controls. Consistently, RBFOX1 expression appeared decreased in post-mortem frontal and temporal cortices of individuals with ASD and prefrontal cortex of individuals with schizophrenia. Brain-functional MRI studies demonstrated that carriers of a common RBFOX1 variant, rs6500744, displayed increased neural reactivity to emotional stimuli, reduced prefrontal processing during cognitive control, and enhanced fear expression after fear conditioning, going along with increased avoidance behaviour. Investigating Rbfox1 neuron-specific knockout mice allowed us to further specify the role of this gene in behaviour. The model was characterised by pronounced hyperactivity, stereotyped behaviour, impairments in fear acquisition and extinction, reduced social interest, and lack of aggression; it provides excellent construct and face validity as an animal model of ASD. In conclusion, convergent translational evidence shows that common variants in RBFOX1 are associated with a broad spectrum of psychiatric traits and disorders, while rare genetic variation seems to expose to early-onset neurodevelopmental psychiatric disorders with and without developmental delay like ASD, in particular. Studying the pleiotropic nature of RBFOX1 can profoundly enhance our understanding of mental disorder vulnerability.

Injury Characteristics, Outcomes, and Health Care Services Use Associated With Nonfatal Injuries Sustained in Mass Shootings in the US, 2012-2019.

Importance: Civilian public mass shootings (CPMSs) in the US result in substantial injuries. However, the types and consequences of these injuries have not been systematically described. Objective: To describe the injury characteristics, outcomes, and health care burden associated with nonfatal injuries sustained during CPMSs and to better understand the consequences to patients, hospitals, and society at large. Design, Setting, and Participants: This retrospective case series of nonfatal injuries from 13 consecutive CPMSs (defined as ≥10 injured individuals) from 31 hospitals in the US from July 20, 2012, to August 31, 2019, used data from trauma logs and medical records to capture injuries, procedures, lengths of stay, functional impairment, disposition, and charges. A total of 403 individuals treated in hospitals within 24 hours of the CPMSs were included in the analysis. Data were analyzed from October 27 to December 5, 2021. Exposures: Nonfatal injuries sustained during CPMSs. Main Outcomes and Measures: Injuries and diagnoses, treating services, procedures, hospital care, and monetary charges. Results: Among the 403 individuals included in the study, the median age was 33.0 (IQR, 24.5-48.0 [range, 1 to >89]) years, and 209 (51.9%) were women. Among the 386 patients with race and ethnicity data available, 13 (3.4%) were Asian; 44 (11.4%), Black or African American; 59 (15.3), Hispanic/Latinx; and 270 (69.9%), White. Injuries included 252 gunshot wounds (62.5%) and 112 other injuries (27.8%), and 39 patients (9.7%) had no physical injuries. One hundred seventy-eight individuals (53.1%) arrived by ambulance. Of 494 body regions injured (mean [SD], 1.35 [0.68] per patient), most common included an extremity (282 [57.1%]), abdomen and/or pelvis (66 [13.4%]), head and/or neck (65 [13.2%]), and chest (50 [10.1%]). Overall, 147 individuals (36.5%) were admitted to a hospital, 95 (23.6%) underwent 1 surgical procedure, and 42 (10.4%) underwent multiple procedures (1.82 per patient). Among the 252 patients with gunshot wounds, the most common initial procedures were general and trauma surgery (41 [16.3%]) and orthopedic surgery (36 [14.3%]). In the emergency department, 148 of 364 injured individuals (40.7%) had 199 procedures (1.34 per patient). Median hospital length of stay was 4.0 (IQR, 2.0-7.5) days; for 50 patients in the intensive care unit, 3.0 (IQR, 2.0-8.0) days (13.7% of injuries and 34.0% of admissions). Among 364 injured patients, 160 (44.0%) had functional disability at discharge, with 19 (13.3%) sent to long-term care. The mean (SD) charges per patient were $64 976 ($160 083). Conclusions and Relevance: Civilian public mass shootings cause substantial morbidity. For every death, 5.8 individuals are injured. These results suggest that including nonfatal injuries in the overall burden of CPMSs may help inform public policy to prevent and mitigate the harm caused by such events.