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The Kuiper Belt is a broad, torus-shaped region in the outer Solar System beyond Neptune’s orbit. It contains primordial planetary building blocks and dwarf planets. NASA’s New Horizons spacecraft conducted a flyby of Pluto and its system of moons on 14 July 2015. New Horizons then continued farther into the Kuiper Belt, adjusting its trajectory to fly close to the small Kuiper Belt object (486958) 2014 MU69 (henceforth MU69; also informally known as Ultima Thule). Stellar occultation observations in 2017 showed that MU69 was ~25 to 35 km in diameter, and therefore smaller than the diameter of Pluto (2375 km) by a factor of ~100 and less massive than Pluto by a factor of ~106. MU69 is located about 1.6 billion kilometers farther from the Sun than Pluto was at the time of the New Horizons flyby. MU69’s orbit indicates that it is a “cold classical” Kuiper Belt object, thought to be the least dynamically evolved population in the Solar System. A major goal of flying past this target is to investigate accretion processes in the outer Solar System and how those processes led to the formation of the planets. Because no small Kuiper Belt object had previously been explored by spacecraft, we also sought to provide a close-up look at such a body’s geology and composition, and to search for satellites, rings, and evidence of present or past atmosphere. We report initial scientific results and interpretations from that flyby.

The past two decades have witnessed substantial interest in sluggish cognitive tempo (SCT), a set of symptoms (e.g., excessive daydreaming, mental confusion, slowed behavior) distinct from attention-deficit/hyperactivity disorder (ADHD) and other psychopathology symptoms. Despite evidence linking SCT to a range of functional outcomes, findings for academic functioning are unclear. The current review summarizes the literature on SCT and academic functioning and offers an agenda for future research. A systematic review was conducted to identify studies assessing SCT and academic outcomes, including academic impairments and performance, in childhood, adolescence, and young adulthood. Sixty studies were retained (53 cross-sectional, 7 longitudinal) from 44 separate samples, with the majority (n = 32, 53%) assessing global ratings of academic impairment and fewer measuring specific academic domains or standardized achievement test scores. Findings were generally consistent in showing SCT to be correlated with global ratings of academic impairment, lower grades, and inconsistently associated with poorer math and reading scores. Findings were more mixed when controlling for ADHD symptoms, intelligence, and/or demographic factors. Overall, SCT is associated with poorer academic functioning, although inconsistencies and key limitations are common across studies. Ten directions for future research are offered to advance understanding of how SCT may be associated with or impact academic functioning.

Third-variable effects, such as mediation and confounding, are core concepts in prevention science, providing the theoretical basis for investigating how risk factors affect behavior and how interventions change behavior. Another third variable, the collider, is not commonly considered but is also important for prevention science. This paper describes the importance of the collider effect as well as the similarities and differences between these three third-variable effects. The single mediator model in which the third variable (T) is a mediator of the independent variable (X) to dependent variable (Y) effect is used to demonstrate how to estimate each third-variable effect. We provide difference in coefficients and product of coefficients estimators of the effects and demonstrate how to calculate these values with real data. Suppression effects are defined for each type of third-variable effect. Future directions and implications of these results are discussed.

Positive risks benefit adolescent development without posing the same public safety concerns as negative risks, but little is understood about the psychological characteristics of positive risk taking. This study explored the shared and unique correlates of positive and negative risk taking in 223 adolescents (48% female) ages 16–20 years (M = 18.1; SD = 0.81). Positive and negative risk taking were both associated with higher sensation seeking. Unlike negative risk taking, positive risk taking was not associated with impulsivity or risk taking on experimental tasks. Further, positive risk taking was associated with lower reward sensitivity, higher punishment sensitivity, and greater school engagement than negative risk taking. The findings offer new insights for prevailing models of adolescent risk behavior and suggest positive risk taking may be particularly beneficial in the school context.

Mindfulness has been associated with fewer negative mental health symptoms during adolescence, but fewer studies have examined longitudinal associations between mindfulness and symptoms in conjunction with two vulnerability factors for psychopathology with mindfulness: rumination and impulsivity. This study examined longitudinal associations between internalizing symptoms (depression, anxiety, stress), mindfulness, rumination, and impulsivity over a one-year period among 352 Spanish adolescents (57.4% girls; M = 14.47, SD = 1.34). Participants completed self-reported measures of symptoms, mindfulness, rumination, and impulsivity at two time points. Mindfulness negatively predicted stress and depressive symptoms, and a bidirectional negative association was found between mindfulness and impulsivity. Impulsivity positively predicted stress, and anxiety positively predicted depressive symptoms, stress, and rumination. This study highlights the importance of mindfulness as a protective factor and impulsivity and anxiety as risk factors for internalizing symptoms throughout adolescence. These findings build on previous studies that examined longitudinal associations between mindfulness and symptoms by including rumination and impulsivity’s roles.

Accounting for both bidirectional and interactive effects between parenting and child temperament can fine-tune theoretical models of the role of parenting and temperament in children’s development of adjustment problems. Evidence for bidirectional and interactive effects between parenting and children’s characteristics of frustration, fear, self-regulation, and impulsivity was reviewed, and an overall model of children’s individual differences in response to parenting is proposed. In general, children high in frustration, impulsivity and low in effortful control are more vulnerable to the adverse effects of negative parenting, while in turn, many negative parenting behaviors predict increases in these characteristics. Frustration, fearfulness, and effortful control also appear to elicit parenting behaviors that can predict increases in these characteristics. Irritability renders children more susceptible to negative parenting behaviors. Fearfulness operates in a very complex manner, sometimes increasing children’s responses to parenting behaviors and sometimes mitigating them and apparently operating differently across gender. Important directions for future research include the use of study designs and analytic approaches that account for the direction of effects and for developmental changes in parenting and temperament over time.

Previous studies have shown mixed results on the relationship between prenatal, birth, and postnatal (“pregnancy-related”) risk factors and attention-deficit/hyperactivity disorder (ADHD). We conducted meta-analyses to identify potentially modifiable pregnancy-related factors associated with ADHD. A comprehensive search of PubMed, Web of Science, and EMBASE in 2014, followed by an updated search in January 2021, identified 69 articles published in English on pregnancy-related risk factors and ADHD for inclusion. Risk factors were included in the meta-analysis if at least three effect sizes with clear pregnancy-related risk factor exposure were identified. Pooled effect sizes were calculated for ADHD overall, ADHD diagnosis, inattention, and hyperactivity/impulsivity. Odds ratios (OR) were calculated for dichotomous measures and correlation coefficients (CC) for continuous measures. Prenatal factors (pre-pregnancy weight, preeclampsia, pregnancy complications, elevated testosterone exposure), and postnatal factors (Apgar score, neonatal illness, no breastfeeding) were positively associated with ADHD overall; the findings for ADHD diagnosis were similar with the exception that there were too few effect sizes available to examine pre-pregnancy weight and lack of breastfeeding. Prenatal testosterone was significantly associated with inattention and hyperactivity/impulsivity. Effect sizes were generally small (range 1.1–1.6 ORs, -0.16–0.11 CCs). Risk factors occurring at the time of birth (perinatal asphyxia, labor complications, mode of delivery) were not significantly associated with ADHD. A better understanding of factors that are consistently associated with ADHD may inform future prevention strategies. The findings reported here suggest that prenatal and postnatal factors may serve as potential targets for preventing or mitigating the symptoms of ADHD.

Body-focused repetitive disorders (BFRBDs) are understudied in youth and understanding of their underlying mechanisms is limited. This study evaluated BFRBD clinical characteristics, and two factors commonly implicated in their maintenance – emotion regulation and impulsivity – in 53 youth aged 11 to 17 years: 33 with BFRBDs and 20 controls. Evaluators administered psychiatric diagnostic interviews. Participants rated BFRBD severity, negative affect, quality of life, family functioning, emotion regulation, distress tolerance, and impulsivity. Youth with BFRBDs showed poorer distress tolerance and quality of life, and higher impulsivity and negative affect than controls, with no differences in family impairment. BFRBD distress/impairment, but not BFRBD severity, correlated with anxiety and depression, and poorer distress tolerance. Findings suggest youth with BFRBDs show clinical patterns aligning with prior research; highlight the role of distress tolerance in child BFRBDs; and suggest the utility of acceptance and mindfulness-based therapies for unpleasant emotions in BFRBDs. Continued research should evaluate factors underlying BFRBDs in youth.

Autism spectrum disorder (ASD) and Attention-deficit/hyperactivity disorder (ADHD) are often comorbid. The purpose of this study is to explore the relationships between ASD and ADHD symptoms by applying causal modeling. We used a large phenotypic data set of 417 children with ASD and/or ADHD, 562 affected and unaffected siblings, and 414 controls, to infer a structural equation model using a causal discovery algorithm. Three distinct pathways between ASD and ADHD were identified: (1) from impulsivity to difficulties with understanding social information, (2) from hyperactivity to stereotypic, repetitive behavior, (3) a pairwise pathway between inattention, difficulties with understanding social information, and verbal IQ. These findings may inform future studies on understanding the pathophysiological mechanisms behind the overlap between ASD and ADHD.

Poor parental mental health and stress have been associated with children’s mental disorders, including attention-deficit/hyperactivity disorder (ADHD), through social, genetic, and neurobiological pathways. To determine the strength of the associations between parental mental health and child ADHD, we conducted a set of meta-analyses to examine the association of parent mental health indicators (e.g., parental depression, antidepressant usage, antisocial personality disorder, and stress and anxiety) with subsequent ADHD outcomes in children. Eligible ADHD outcomes included diagnosis or symptoms. Fifty-eight articles published from 1980 to 2019 were included. We calculated pooled effect sizes, accounting for each study’s conditional variance, separately for test statistics based on ADHD as a dichotomous (e.g., diagnosis or clinical cutoffs) or continuous measurement (e.g., symptoms of ADHD subtypes of inattentiveness and hyperactivity/impulsivity). Parental stress and parental depression were significantly associated with increased risk for ADHD overall and both symptoms and diagnosis. Specifically, maternal stress and anxiety, maternal prenatal stress, maternal depression, maternal post-partum depression, and paternal depression were positively associated with ADHD. In addition, parental depression was associated with symptoms of ADHD inattentive and hyperactive/impulsive subtypes. Parental antisocial personality disorder was also positively associated with ADHD overall and specifically ADHD diagnosis. Prenatal antidepressant usage was associated with ADHD when measured dichotomously only. These findings raise the possibility that prevention strategies promoting parental mental health and addressing parental stress could have the potential for positive long-term impacts on child health, well-being, and behavioral outcomes.