Eric D. Kolaczyk, Lizhen Lin, Steven Rosenberg, Jackson Walters, Jie Xu.

Source: The Annals of Statistics, Volume 48, Number 1, 514--538.

Abstract:
It is becoming increasingly common to see large collections of network data objects, that is, data sets in which a network is viewed as a fundamental unit of observation. As a result, there is a pressing need to develop network-based analogues of even many of the most basic tools already standard for scalar and vector data. In this paper, our focus is on averages of unlabeled, undirected networks with edge weights. Specifically, we (i) characterize a certain notion of the space of all such networks, (ii) describe key topological and geometric properties of this space relevant to doing probability and statistics thereupon, and (iii) use these properties to establish the asymptotic behavior of a generalized notion of an empirical mean under sampling from a distribution supported on this space. Our results rely on a combination of tools from geometry, probability theory and statistical shape analysis. In particular, the lack of vertex labeling necessitates working with a quotient space modding out permutations of labels. This results in a nontrivial geometry for the space of unlabeled networks, which in turn is found to have important implications on the types of probabilistic and statistical results that may be obtained and the techniques needed to obtain them.

Lekha Patel, Nils Gustafsson, Yu Lin, Raimund Ober, Ricardo Henriques, Edward Cohen.

Source: The Annals of Applied Statistics, Volume 13, Number 3, 1397--1429.

Abstract:
Fluorescing molecules (fluorophores) that stochastically switch between photon-emitting and dark states underpin some of the most celebrated advancements in super-resolution microscopy. While this stochastic behavior has been heavily exploited, full characterization of the underlying models can potentially drive forward further imaging methodologies. Under the assumption that fluorophores move between fluorescing and dark states as continuous time Markov processes, the goal is to use a sequence of images to select a model and estimate the transition rates. We use a hidden Markov model to relate the observed discrete time signal to the hidden continuous time process. With imaging involving several repeat exposures of the fluorophore, we show the observed signal depends on both the current and past states of the hidden process, producing emission probabilities that depend on the transition rate parameters to be estimated. To tackle this unusual coupling of the transition and emission probabilities, we conceive transmission (transition-emission) matrices that capture all dependencies of the model. We provide a scheme of computing these matrices and adapt the forward-backward algorithm to compute a likelihood which is readily optimized to provide rate estimates. When confronted with several model proposals, combining this procedure with the Bayesian Information Criterion provides accurate model selection.

MN Shadlen
Feb 15, 1996; 16:1486-1510
Articles

Nicotine addiction, through smoking, is the principal cause of preventable mortality worldwide. Human genome-wide association studies have linked polymorphisms in the CHRNA5-CHRNA3-CHRNB4 gene cluster, coding for the α5, α3, and β4 nicotinic acetylcholine receptor (nAChR) subunits, to nicotine addiction. β4*nAChRs have been implicated in nicotine withdrawal, aversion, and reinforcement. Here we show that β4*nAChRs also are involved in non-nicotine-mediated responses that may predispose to addiction-related behaviors. β4 knock-out (KO) male mice show increased novelty-induced locomotor activity, lower baseline anxiety, and motivational deficits in operant conditioning for palatable food rewards and in reward-based Go/No-go tasks. To further explore reward deficits we used intracranial self-administration (ICSA) by directly injecting nicotine into the ventral tegmental area (VTA) in mice. We found that, at low nicotine doses, β4KO self-administer less than wild-type (WT) mice. Conversely, at high nicotine doses, this was reversed and β4KO self-administered more than WT mice, whereas β4-overexpressing mice avoided nicotine injections. Viral expression of β4 subunits in medial habenula (MHb), interpeduncular nucleus (IPN), and VTA of β4KO mice revealed dose- and region-dependent differences: β4*nAChRs in the VTA potentiated nicotine-mediated rewarding effects at all doses, whereas β4*nAChRs in the MHb-IPN pathway, limited VTA-ICSA at high nicotine doses. Together, our findings indicate that the lack of functional β4*nAChRs result in deficits in reward sensitivity including increased ICSA at high doses of nicotine that is restored by re-expression of β4*nAChRs in the MHb-IPN. These data indicate that β4 is a critical modulator of reward-related behaviors.

SIGNIFICANCE STATEMENT Human genetic studies have provided strong evidence for a relationship between variants in the CHRNA5-CHRNA3-CHRNB4 gene cluster and nicotine addiction. Yet, little is known about the role of β4 nicotinic acetylcholine receptor (nAChR) subunit encoded by this cluster. We investigated the implication of β4*nAChRs in anxiety-, food reward- and nicotine reward-related behaviors. Deletion of the β4 subunit gene resulted in an addiction-related phenotype characterized by low anxiety, high novelty-induced response, lack of sensitivity to palatable food rewards and increased intracranial nicotine self-administration at high doses. Lentiviral vector-induced re-expression of the β4 subunit into either the MHb or IPN restored a "stop" signal on nicotine self-administration. These results suggest that β4*nAChRs provide a promising novel drug target for smoking cessation.

MECP2 gain-of-function and loss-of-function in genetically engineered monkeys recapitulates typical phenotypes in patients with autism, yet where MECP2 mutation affects the monkey brain and whether/how it relates to autism pathology remain unknown. Here we report a combination of gene–circuit–behavior analyses including MECP2 coexpression network, locomotive and cognitive behaviors, and EEG and fMRI findings in 5 MECP2 overexpressed monkeys (Macaca fascicularis; 3 females) and 20 wild-type monkeys (Macaca fascicularis; 11 females). Whole-genome expression analysis revealed MECP2 coexpressed genes significantly enriched in GABA-related signaling pathways, whereby reduced β-synchronization within fronto-parieto-occipital networks was associated with abnormal locomotive behaviors. Meanwhile, MECP2-induced hyperconnectivity in prefrontal and cingulate networks accounted for regressive deficits in reversal learning tasks. Furthermore, we stratified a cohort of 49 patients with autism and 72 healthy controls of 1112 subjects using functional connectivity patterns, and identified dysconnectivity profiles similar to those in monkeys. By establishing a circuit-based construct link between genetically defined models and stratified patients, these results pave new avenues to deconstruct clinical heterogeneity and advance accurate diagnosis in psychiatric disorders.

SIGNIFICANCE STATEMENT Autism spectrum disorder (ASD) is a complex disorder with co-occurring symptoms caused by multiple genetic variations and brain circuit abnormalities. To dissect the gene–circuit–behavior causal chain underlying ASD, animal models are established by manipulating causative genes such as MECP2. However, it is unknown whether such models have captured any circuit-level pathology in ASD patients, as demonstrated by human brain imaging studies. Here, we use transgenic macaques to examine the causal effect of MECP2 overexpression on gene coexpression, brain circuits, and behaviors. For the first time, we demonstrate that the circuit abnormalities linked to MECP2 and autism-like traits in the monkeys can be mapped to a homogeneous ASD subgroup, thereby offering a new strategy to deconstruct clinical heterogeneity in ASD.

Behavior can be guided by neuronal activity in visual, auditory, or somatosensory cerebral cortex, depending on task requirements. In contrast to this flexible access of cortical signals, several observations suggest that behaviors depend more on neurons in later areas of visual cortex than those in earlier areas, although neurons in earlier areas would provide more reliable signals for many tasks. We recorded from neurons in different levels of visual cortex of 2 male rhesus monkeys while the animals did a visual discrimination task and examined trial-to-trial correlations between neuronal and behavioral responses. These correlations became stronger in primary visual cortex as neuronal signals in that area became more reliable relative to the other areas. The results suggest that the mechanisms that read signals from cortex might access any cortical area depending on the relative value of those signals for the task at hand.

SIGNIFICANCE STATEMENT Information is encoded by the action potentials of neurons in various cortical areas in a hierarchical manner such that increasingly complex stimulus features are encoded in successive stages. The brain must extract information from the response of appropriate neurons to drive optimal behavior. A widely held view of this decoding process is that the brain relies on the output of later cortical areas to make decisions, although neurons in earlier areas can provide more reliable signals. We examined correlations between perceptual decisions and the responses of neurons in different levels of monkey visual cortex. The results suggest that the brain may access signals in any cortical area depending on the relative value of those signals for the task at hand.

See how researchers at Smithsonian's National Zoo are trying to glean insight into elephant foraging behavior and more.

OBJECTIVES:

To summarize baseline data and lessons learned from the Autism Learning Health Network, designed to improve care and outcomes for children with autism spectrum disorder (ASD). We describe challenging behaviors, co-occurring medical conditions, quality of life (QoL), receipt of recommended health services, and next steps.

Prematurely born children have an increased prevalence of behavioral problems in the long term. Knowledge regarding the effects of early intervention programs is sparse, and more randomized controlled trials are warranted.

A modified version of the Mother-Infant Transaction Program showed beneficial effects on behavioral outcomes reported by both parents of preterm infants with birth weights of <2000 g at a corrected age of 5 years. (Read the full article)

Traumatic brain injury in school-aged children is associated with intellectual, behavioral, and social deficits. Research into outcomes of children injured before 3 years of age is limited despite data suggesting a high incidence of injury in this age group.

Results show that a moderate to severe traumatic brain injury before 3 years of age is associated with lowered cognitive function. Furthermore, this study highlights the link between social disadvantage and poor outcomes after traumatic brain injury in early childhood. (Read the full article)

Childhood UV light exposures, specifically sunburns, have been shown to be associated with melanoma development later in life.

To date, most studies in this age group have been cross sectional in nature. This is the first prospective study of sunburn and sun behaviors in this age group. (Read the full article)

The social and emotional burdens of ostracism are well known, but few studies have tested whether ostracism adversely alters physical activity behaviors that may result in maintenance of childhood obesity.

This is the first study to experimentally assess the effect of simulated ostracism, or social exclusion, on physical activity behavior in children. Ostracism reduced accelerometer counts by 22% and increased time allocated to sedentary behaviors by 41%. (Read the full article)

Strategies to assist patients in achieving optimal chronic disease self-management are critical. The complex family and regimen issues surrounding pediatric type 1 diabetes management suggest the need to integrate such strategies into routine clinical care.

This study demonstrates the efficacy of a practical, low-intensity behavioral intervention delivered during routine care for improving glycemic outcomes. Findings indicate that the approach may offer a potential model for integrating medical and behavioral sciences to improve health care. (Read the full article)

Sleep-disordered breathing is associated with neurobehavioral morbidity in children. Prior related research has generally been cross-sectional or short (ie, 1–2 years) follow-up studies of a single symptom (ie, snoring, obstructive sleep apnea, mouth breathing), with limited control for confounders.

Sleep-disordered breathing was assessed as a trajectory of combined symptoms from 6 months to 69 months, in more than 11 000 children. Sleep-disordered breathing was associated with 40% and 60% more behavioral difficulties at 4 and 7 years, respectively. (Read the full article)

Preterm infants are at increased risk of behavioral problems, which has been associated with maternal distress. Paternal psychological well-being is less studied. Parents’ concerns may affect their perceptions or attitudes and have negative effects on the behavior of the child.

Parents report more behavior problems in VLBW children at age 3 if they themselves have had symptoms of depression, parenting stress, or weak sense of coherence. Also, the paternal psychological well-being contributes to the behavioral development of a preterm child. (Read the full article)

Prenatal methamphetamine exposure has been related to deficits in fetal growth, changes in infant neurobehavior, and fine motor deficits, but little is known about its developmental effects on behavior problems in early childhood.

This is the first prospective study to identify behavior problems associated with prenatal methamphetamine exposure. Mood difficulties and acting-out behavior are increased in exposed children by age 3 years. Early identification and intervention may prevent escalation into delinquency and psychopathology. (Read the full article)

Although developmental care in NICUs reduces the stress experienced by preterm infants, the actual level of developmental care may vary and little is known about how the level of developmental care relates to preterm infants’ neurobehavioral performance.

The study demonstrates the relationship between variations in developmental care in NICUs and the neurobehavior of preterm infants. Infants from NICUs with high-quality developmental care compared with infants from units with low quality of care evidenced a better neurobehavioral profile. (Read the full article)

Although several randomized trials have examined the efficacy of serotonin receptor inhibitors in the treatment of repetitive behaviors, there still remains clinical uncertainty as to whether these agents are effective in treating such behaviors in children and adults with autism spectrum disorders.

The goal of this meta-analysis was to examine randomized trials of serotonin receptor inhibitors for treating repetitive behaviors in autism spectrum disorders. Although a small but significant effect of these agents was observed, this effect is likely due to the selective publication of trial results. (Read the full article)

Traditional health-risk behaviors, such as problem drinking, smoking, marijuana use, and unsafe sexual behavior are interrelated and not isolated events in the life of adolescents. New health-risk behaviors are emerging: risky music-listening behaviors, which may induce hearing loss.

Risky music-listening behaviors are highly associated with traditional health-risk behaviors. Risky MP3-player listeners are often cannabis users. Frequent visitors of music venues are less often cannabis users, but are often binge drinkers and have sexual intercourse without using a condom. (Read the full article)

Known rates of nonsuicidal self-injury, hurting oneself without the intent to die, are between ~7% and 24% in samples of early adolescents and older adolescents, yet research has not reported rates for youth younger than 11 years old.

Children as young as 7 years old report engaging in nonsuicidal self-injury. There is a grade by gender interaction for nonsuicidal self-injury, such that ninth-grade girls report the greatest rates of engagement and do so by cutting themselves. (Read the full article)

There are limited cross-sectional data from observational studies of adolescents showing that regular participation in physical activity is associated with a higher quality of life status, whereas time spent in screen-based entertainment is associated with a poorer quality of life.

Adolescents who were physically active (particularly engaging in outdoor activity) over a 5-year period had higher quality of life than their less active peers. Conversely, high levels of screen-based entertainment over 5 years negatively affected quality of life status. (Read the full article)

Comprehensive lifestyle interventions for adolescent weight management, including diet, physical activity, and behavioral intervention, have been found to demonstrate modest, short-term success. However, very little is known about the long-term effectiveness of adolescent behavioral weight management trials.

This randomized controlled trial demonstrates that two 16-week group-based behavioral weight loss programs, when combined with either aerobic exercise or peer-based adventure therapy, produced sustained improvements in BMI among overweight/obese adolescents through 24 months. (Read the full article)

In humans, evidence for an association between maternal caffeine intake during pregnancy and alterations in fetal brain development with persistent alterations in the offspring’s brain and behavior in later life is inconclusive.

Prenatal caffeine intake is not associated with a higher risk for behavior problems in young children. Results do not provide evidence to advise pregnant women to reduce their caffeine intake to prevent problem behavior in their children. (Read the full article)

Childhood obesity is already prevalent by preschool age, particularly among Latinos. Parents have tremendous influence on factors that contribute to childhood obesity (eg, diet, physical activity); thus, family plays a crucial role in pediatric obesity prevention.

This randomized controlled trial examined the effect of a behavioral intervention involving Latino-American parent–preschool-aged child dyads. The intervention resulted in reductions in absolute BMI across the 3-month study period, with patterns suggesting the largest effect for obese children. (Read the full article)

Loud snoring, which spikes at ~2 to 3 years of age, has been associated with behavior problems in school-aged children in cross-sectional studies, but no longitudinal studies have quantified predictors and the behavioral impact of persistent snoring in preschool-aged children.

Persistent loud snoring, which occurs in 9% of children 2 to 3 years of age, is linked with behavior problems. Higher socioeconomic status and a history of breastfeeding were associated with lower rates of transient and persistent snoring in young children. (Read the full article)

Childhood obesity occurs in 20% of children before they enter kindergarten. Treatment is difficult, making prevention desirable, but little is known about effective methods using anticipatory guidance to prevent obesity in pediatric primary care.

This study provides a comparison of 2 approaches versus usual care using anticipatory guidance to improve infant feeding during the first year of life, and demonstrates positive specific feeding behavior differences at 1 year in the intervention groups. (Read the full article)

Behavioral techniques effectively reduce infant sleep problems and associated maternal depression in the short- to medium-term (4–16 months’ postintervention). Despite their effectiveness, theoretical concerns persist about long-term harm on children’s emotional development, stress regulation, mental health, and the child-parent relationship.

Behavioral sleep techniques did not cause long-lasting harms or benefits to child, child-parent, or maternal outcomes. Parents and health professionals can feel comfortable about using these techniques to reduce the population burden of infant sleep problems and maternal depression. (Read the full article)

Infant behavioral dysregulation is a common concern, involving irritability, excessive crying, and problems with feeding and sleep. Previous research into its behavioral outcomes has been limited by small cohorts and short follow-up, and findings have been contradictory.

Long-term follow-up of a large cohort showed that infant behavioral dysregulation was a risk factor for maternal-reported behavior concerns at 5 and 14 years, but was unrelated to young adult mental health outcomes. (Read the full article)

School-Wide Positive Behavioral Interventions and Supports (SWPBIS) is a widely used universal prevention strategy currently implemented in >16 000 schools across the United States. Previous research has shown positive effects on school climate and school-level discipline problems.

This study reports multilevel results on data from a 4-year randomized controlled effectiveness trial of SWPBIS in 37 elementary schools. Results indicate significant impacts on children’s aggressive behavior problems, concentration problems, office discipline referrals, emotion regulation, and prosocial behavior. (Read the full article)

Stress in parents has been shown to be related to child obesity.

The presence of multiple parent stressors was related to child obesity, and parent perception of stress was related to child fast-food consumption. Stress in parents may be an important risk factor for child obesity and related behaviors. (Read the full article)

Today’s adolescents increasingly use the Internet to explore their sexual identity. There is public concern that the Internet, because of its accessibility, affordability, and anonymity, stimulates adolescents to engage in online sexual risk behavior (eg, sending sexual images to strangers).

This 4-wave panel study is the first to delineate the typical development of online sexual risk behavior, its relationship with offline sexual risk behavior, and the factors (eg, sensation seeking, family cohesion, life satisfaction, education, online communication) that predict both behaviors. (Read the full article)

Emphasis on muscularity has increased in recent decades. Identifying adolescent populations at risk for unhealthy muscle-enhancing behaviors is of considerable importance, yet recent research in the United States is limited in terms of sample diversity and behaviors of interest.

Muscle-enhancing behaviors were common for both boys and girls, and rates were higher than reported previously. Adolescents in high school, of Asian background, in overweight/obese BMI categories, and involved in sports reported significantly greater use than other youth. (Read the full article)

Prenatal cocaine exposure is associated with the trajectories of childhood behavior problems. Exposure effects may also be related to maternal use of other substances during pregnancy, and risk factors other than prenatal exposure may augment the detrimental cocaine effects.

The balance between cumulative risk and protective indexes predicts behavior outcomes, independent of prenatal drug exposure. A high protective index even with a high level of risks can mitigate the detrimental effects of drug exposure on behavior problem trajectory. (Read the full article)

Low birth weight (LBW) infants (<2500 g) are at risk for cognitive and behavioral problems later in life. During infancy, they are also at risk for iron deficiency, which has been associated with impaired neurodevelopment in other high-risk groups.

Iron supplementation during the first 6 months of life to LBW infants reduces the risk of behavioral problems at 3.5 years. Mild iron deficiency in infancy may be an important, preventable contributor to behavioral problems in children born with LBW. (Read the full article)

Paternal mental disorders during the postnatal period are associated with an increased risk for behavioral and emotional problems in their children; however, less is known about the effect of fathers’ mental health during pregnancy on children’s development.

The study demonstrated a positive association between fathers’ prenatal mental health and their children’s subsequent socioemotional and behavioral development. Psychological distress in fathers was associated with a risk for emotional difficulties in their children at 36 months of age. (Read the full article)

Evidence regarding effectively screening and counseling adolescents about unhealthy alcohol use is accumulating. Young adults aged 18 to 24, those most at risk for excess alcohol consumption, are often not asked or counseled by physicians about unhealthy alcohol use.

In 2010 among US 10th graders (age 16), 36% drank, 28% binged, and 23% were drunk in the past month; although 82% saw a doctor, 54% were asked about drinking but only 17% were advised to reduce or stop drinking. (Read the full article)

The rise in type 2 diabetes in youth is a major public health concern thought to be partially due to decreasing activity levels and increasing obesity. The role of sedentary time as a possible contributor also needs to be examined.

Measured objectively, obese youth, with or without type 2 diabetes, spend little time in moderate to vigorous physical activity. Those with type 2 diabetes, however, were significantly more sedentary than their obese counterparts, identifying an important area for future intervention efforts. (Read the full article)

Many studies have identified an association between television viewing and antisocial behavior, although very few have been able to demonstrate a cause-and-effect sequence. The issue of whether excessive television viewing contributes to antisocial behavior remains controversial.

Excessive television viewing during childhood and adolescence was associated with objective and subjective measures of antisocial behavior in adulthood. These associations were not explained by preexisting antisocial tendencies or other potential confounders. Excessive television appears to have long-term psychosocial consequences. (Read the full article)

While obesity-promoting eating, sedentary and physical activity behaviors, and increased prevalence of adiposity are evident from early life, few high-quality studies have evaluated interventions that seek to influence the development of these behaviors in very early childhood.

This study highlights the receptivity of first-time parents to interventions focused on their new infant’s eating and active play and provides evidence of effectiveness on some obesity-promoting behaviors in very early childhood. (Read the full article)

Distracted driving due to texting while driving (TWD) has emerged as an important teenage safety issue. Previous studies have shown that the self-reported prevalence of TWD among teenagers varies widely.

In 2011, 45% of US high school students aged ≥16 years reported TWD during the past 30 days. TWD was positively associated with other risky motor vehicle behaviors; this association strengthened as frequency of TWD increased. (Read the full article)

Feeding difficulties often emerge during the neonatal period and affect neonatal growth. Growth throughout the first years of life is associated with children’s IQ scores and risk of behavioral problems.

Among infants born full term (≥37 weeks’ gestation) with birth weight ≥2500 g, gain in weight and head circumference during the neonatal period is associated with higher IQ, but not with behavior at 6.5 years of age. (Read the full article)

The number of overweight and obese children has dramatically increased in recent decades. To combat this trend, information on possible gender-related differences in risk factors of overweight and obesity is critical.

This study examines associations of gender and physiologic and behavior measurements with potential cardiovascular risk. Lunch consumption and screen time were associated with weight; however, other associations with weight differ by gender. This information can be used to tailor future interventions. (Read the full article)

The prevalence of overweight and obesity in US adolescents has increased over the last century. However, recent evidence indicates a potential change in this trend. Parallel trends in adolescent behaviors that drive this epidemic have not been well studied.

Analyses of recent data indicate the prevalence of overweight and obesity may be stabilizing. Over the same period, adolescent physical activity, breakfast eating, and fruit and vegetable consumption increased and television viewing and consumption of sweets and sweetened beverages decreased. (Read the full article)

Prenatal exposures to diverse pollutants and psychosocial stressors have been shown independently to adversely affect child development. Less is known about the potential interactions between these factors, although they commonly co-occur, especially in disadvantaged populations.

The combination of high prenatal exposure to environmental polycyclic aromatic hydrocarbons and maternal demoralization adversely affects child behavior, and maternal demoralization has a greater effect among children with high prenatal polycyclic aromatic hydrocarbon exposure for a majority of behavioral symptoms. (Read the full article)

Links between clinically diagnosed sleep problems and adverse behavioral outcomes are well documented. However, in nonclinical populations, causal links between disrupted sleep and the development of behavioral difficulties are far from clear.

Seven-year-old children with nonregular bedtimes had more behavioral difficulties than children who had regular bedtimes. There were clear dose–response relationships, and the effects of not having regular bedtimes appeared to be reversible. (Read the full article)

Pediatric functional abdominal pain is common and costly. Cognitive behavior therapy (CBT) is a promising treatment for these complaints, but solid evidence for its effectiveness is lacking.

This randomized controlled trial shows that CBT reduces abdominal pain in 60% of children 1 year after treatment. Six sessions of CBT delivered by trained master’s students in psychology were equally effective as 6 visits to an experienced pediatrician. (Read the full article)

Use of behavioral health (BH) screens in pediatrics have increased identification of children with BH issues. Screening rates increased in Massachusetts after it was mandated, as did the volume of some mental health services.

This is the first study of children after Massachusetts mandated behavioral screening began. Almost 40% of children who screened positive were newly identified. Being male, having a BH history, and being in foster care predicted a positive screen. (Read the full article)

Early timing of puberty and affiliation with deviant friends are associated with higher levels of delinquent and aggressive behavior. Early-maturing adolescents tend to affiliate with more-deviant peers and appear more susceptible to negative peer influences.

Young early-maturing girls do not yet associate with deviant friends but are more susceptible to negative peer influences. Early puberty effects are stable over time for delinquency but dissipate for aggression. Most of these relationships are invariant across race/ethnicity. (Read the full article)

Youth are frequent consumers of movies that contain high levels of violence, and violent content in films, especially those rated PG-13, has been increasing over time.

Content analyses seldom examine how violence is portrayed with other health risk behaviors, such smoking, drinking, and sex. This study presents an innovative way to characterize on-screen violent content and demonstrates the extent to which risk behaviors co-occur within films. (Read the full article)