Cross-sectional associations between objectively measured sleep characteristics and body mass index in European children and adolescents.

BACKGROUND: Short sleep duration has been found to be associated with a higher risk for overweight and obesity. However, previous studies have mainly relied on subjective measures of sleep duration and other sleep characteristics (eg quality, timing) have often been neglected. Therefore, we aimed to investigate associations between several, mainly objectively measured sleep characteristics and body mass index (BMI). Further, we aimed to identify distinct sleep subtypes based on these sleep characteristics and to study their association with BMI. METHODS: Children aged 9-16 years participating in the European I.Family study (N = 559, 51.2% girls, 32.9% overweight/obese) wore an accelerometer for one week on their wrist and recorded their daily wake-up and lights-off times in a sleep diary. Information on sleep duration, sleep efficiency and sleep latency was derived. To identify sleep subtypes, we conducted a latent class analysis using all five sleep variables. Associations between single sleep variables, sleep subtype and age- and sex-specific BMI z-score were investigated using linear mixed-effects regression models to accommodate clustering among siblings. RESULTS: No statistically significant associations were observed between the single sleep variables (sleep duration, sleep efficiency, sleep latency, wake-up and lights-off times) and BMI z-score. Four sleep subtypes were identified and children were assigned to one of the groups based on their highest probability for latent group membership: "early birds" (17.5% of the sample), "short sleep duration" (14.7%), "optimal sleep" (47.6%) and "poor sleep quality" (20.2%). Sleep subtype was not associated with BMI z-score. CONCLUSIONS: Using objective sleep data, we did not find convincing evidence for associations between the sleep variables under investigation and BMI.

School- and Leisure Time Factors Are Associated With Sitting Time of German and Irish Children and Adolescents During School: Results of a DEDIPAC Feasibility Study.

Objective: The study aims to investigate to what extent school- and leisure time-related factors are associated with sedentary behavior during school in German and Irish children and adolescents. Methods: The study based on a sample of 198 children and adolescents surveyed in 2015. Sedentary and activity behavior were measured using the activPAL physical activity monitor. Information on socio-economic status, school- and leisure-time related factors were provided by questionnaires. Associations between school- and leisure time-related factors and sedentary time during school were estimated using linear multi-level models. Results: Access to play equipment in school was associated with reduced sitting time (hours/day) of children (ß = 0.78; 95%CI = 0.06-1.48). Media devices in bedroom and assessing the neighborhood as activity friendly was associated with increased sitting time of children (ß = 0.92; 95%CI = 0.12-1.72 and ß = 0.30; 95%CI = 0.01-0.60, respectively). The permission to use media devices during breaks was associated with increased sitting time (hours/day) of adolescents (ß = 0.37; 95% CI = 0.06-0.69). A less safe traffic surrounding at school was associated with reduced sitting time of adolescents (ß = -0.42; 95% CI = -0.80 to -0.03). Conclusion: Results suggest that school- and leisure time-related factors are associated to the sedentary behavior during school. We suggest that future strategies to reduce sedentary time should consider both contexts.

Cross-Sectional and Longitudinal Associations Between Psychosocial Well-Being and Cardiometabolic Markers in European Children and Adolescents.

OBJECTIVE: Research examining aspects of positive mental health as potential predictors of cardiometabolic health in young populations is scarce. We investigated the associations between psychosocial well-being and waist circumference (WAIST), blood pressure (BP), the homeostasis model assessment for insulin resistance, triglycerides, and high-density lipoprotein cholesterol considering life-style factors as mediators. METHODS: Data of European children and adolescents participating in the baseline (2007/2008), first follow-up (FU1; 2009/2010) and second follow-up (FU2; 2013/2014) examinations of the IDEFICS/I.Family study were used (ncross-sectional = 6519; nlongitudinal = 1393). A psychosocial well-being score was calculated from 16 items on emotional well-being, self-esteem, and social relationships (0-48 points). Cardiometabolic markers were transformed to age- and sex-specific and, in case of BP, also height-specific z scores. Life-style factors included diet, physical activity, sleep, and electronic media use. Applying path analysis, we obtained unstandardized estimates of direct and indirect effects of well-being on cardiometabolic markers. RESULTS: Cross-sectionally, well-being score showed a negative direct and a negative indirect effect through life-style factors on WAIST z score (estimate per 4-point increase, -0.051 [p = .001] and -0.014 [p < .001], respectively). Longitudinally, positive changes in well-being score between baseline and FU1 and between FU1 and FU2, respectively, demonstrated negative indirect effects through life-style factorsFU2 on WAIST z scoreFU2. Both cross-sectionally and longitudinally, higher levels of well-being showed lowering indirect effects on homeostasis model assessment, BP, and triglyceride z scores and an increasing indirect effect on high-density lipoprotein cholesterol z score through both life-style factors and WAIST z score. CONCLUSIONS: These results supported our hypothesis that a healthier life-style may be one mechanism through which higher well-being is linked with lower abdominal obesity and fewer other cardiometabolic disorders in young populations. TRIAL REGISTRATION: Pan-European IDEFICS/I.Family children cohort, ISRCTN registry number: ISRCTN62310987 (http://www.isrctn.com/ISRCTN62310987).

Associations between sleep duration and insulin resistance in European children and adolescents considering the mediating role of abdominal obesity.

BACKGROUND: Short sleep duration has been suggested to lead to insulin resistance both directly by altering glucose metabolism and indirectly through obesity. This study aims to investigate associations between nocturnal sleep duration and insulin resistance considering abdominal obesity as a mediator. METHODS: We analysed data of 3 900 children aged 2-15 years participating in the second (2009/10) and third (2013/14) examination wave of the European IDEFICS/I.Family study (hereafter referred to as baseline and follow-up). Information on nocturnal sleep duration was collected by questionnaires and age-standardised (SLEEP z-score). The homeostasis model assessment (HOMA) was calculated from fasting insulin and fasting glucose obtained from blood samples; waist circumference (WAIST) was measured with an inelastic tape. HOMA and WAIST were used as indicators for insulin resistance and abdominal obesity, respectively, and transformed to age- and sex-specific z-scores. Cross-sectional and longitudinal associations between SLEEP z-score and HOMA z-score were investigated based on a path model considering WAIST z-score as a mediator adjusting for relevant confounders. RESULTS: Cross-sectionally, baseline SLEEP z-score was negatively associated with baseline WAIST z-score (unstandardised effect estimate -0.120, 95% confidence interval [-0.167; -0.073]). We observed no direct effect of baseline SLEEP z-score on baseline HOMA z-score but a negative indirect effect through baseline WAIST z-score (-0.042 [-0.058; -0.025]). Longitudinally, there was no direct effect of baseline SLEEP z-score on HOMA z-score at follow-up but a negative indirect effect through both baseline WAIST z-score and WAIST z-score at follow-up (-0.028 [-0.040; -0.016]). CONCLUSIONS: Our results do not support the hypothesis of an association between short sleep duration and insulin resistance independent of abdominal obesity. However, longer sleep duration may exert short and long term beneficial effects on insulin resistance through its beneficial effects on abdominal obesity.

Circulating miRNAs are associated with sleep duration in children/adolescents: Results of the I.Family Study.

NEW FINDINGS: What is the central question of this study? Are differential patterns of circulating miRNAs associated with sleep duration in normal-weight European children and adolescents? What is the main finding and its importance? Differences in the expression level of circulating miR-26b-3p and miR-485-5p are positively associated with total sleep duration in healthy normal-weight children and adolescents. ABSTRACT: It is commonly recognized that sleep is essential for children's health, and that insufficient sleep duration is associated with negative health outcomes. In humans, sleep duration and quality are influenced by genetic, environmental and social factors. Epigenetic mechanisms, likewise, regulate circadian rhythms and sleep patterns. In the present study, we aimed to identify circulating microRNAs associated with sleep duration in a subsample of normal-weight European children/adolescents (n = 111) participating in the I.Family Study. Subjects were divided into two groups based upon self-reported sleep duration, according to the recommended amount of sleep for paediatric populations. Sleep needs for children <13 years were at least 9 h per day, and for children >13 were at least 8 h per day. There were group differences (short sleepers versus normal sleepers) in circulating levels of miR-26b-3p (mean (95% CI) = 2.0 (1.3-2.7) versus 2.3 (1.9-2.7), P = 0.05) and miR-485-5p (mean (95% CI) = 0.6 (0.3-0.9) versus 0.9 (0.7 - 1.0), P < 0.001), adjusting for country of origin, age, sex, pubertal status, screen time and highest educational level of parents. Our findings show for the first time that sleep duration reflects the profile of specific circulating microRNAs in school-aged children and adolescents. It is conceivable that epigenetic modifications, mainly related to circadian rhythm control, may be modulated or interfere with sleep duration.

Relationship between perception of emotional home atmosphere and fruit and vegetable consumption in European adolescents: results from the I.Family survey.

OBJECTIVE: Consumption of fruits and vegetables (F&V) among adolescents falls below recommendations in many Western countries. The impact of social and emotional aspects of family life on adolescent dietary behaviour may contribute to this, yet remains under-investigated. The present study examines the association between adolescents' perceptions of emotional home atmosphere (EHA) and their F&V consumption frequency. DESIGN: An FFQ was used to assess F&V consumption frequency. EHA was assessed by an eight-item measure with three subscales: perceived home warmth, strictness and relational tension. EHA subscales were used as binary variables: a score equal to or above the median value was considered as a higher perception, while a score below the median was considered as a lower perception of the EHA in question. Country differences in meeting the European 5-a-day recommendations were described. Further, the association between EHA and F&V consumption frequency was investigated using multiple linear regression. SETTING: Regional examination centres in eight European countries. PARTICIPANTS: Adolescents (n 3196) aged 12-18 years. RESULTS: The mean F&V consumption frequency was 3·27 (sd 2·84) times/d. Only 16·1 % of boys and 18 % of girls in our study sample met the recommendation of five F&V daily. After controlling for age, sex, education level of the parents and country of origin, perceived home warmth was associated with a 16 (95 % CI 9, 22) % higher F&V consumption frequency (P < 0·001). CONCLUSIONS: F&V consumption frequency was suboptimal in the survey areas. Interventions targeting perceived warmth as a component of EHA could potentially have a positive effect on adolescents' dietary behaviour.

Emotion-driven impulsiveness but not decision-making ability and cognitive inflexibility predicts weight status in adults.

In this study we aimed to determine whether decision-making ability, cognitive inflexibility and emotion-driven impulsiveness are associated with weight status as expressed by body mass index (BMI), percentage body fat, waist circumference and skinfold thickness in adults from eight different European countries taking part in the I.Family study. The Bechara Gambling Task was used to assess decision-making ability (n = 1717). The Berg Card Sorting Test was used to measure cognitive inflexibility (n = 1509). Lastly, the negative urgency subscale from the UPPS-P Impulsive Behavior Scale was used to measure emotion-driven impulsiveness (n = 4450). Hierarchical regression analyses showed that more emotion-driven impulsiveness was statistically significantly associated with a higher BMI, a higher percentage body fat, and a larger waist circumference in adults, controlling for age, sex, socioeconomic status, country and binge eating; but not with skinfold thickness. Cognitive inflexibility and decision-making ability were not statistically significantly associated with any of the weight status related variables. These results support that impulsivity in response to negative emotions, but not decision-making ability or cognitive inflexibility, is associated with the susceptibility to excessive weight (as indicated by a higher BMI, a higher percentage body fat, and a larger waist circumference). In people behaving impulsively when emotional, focusing on reducing negative affect or improving coping skills is of interest in interventions targeting obesity. CLINICAL TRIAL REGISTRATION: The I.Family study is registered in the ISRCTN registry (ISRCTN62310987) on February 23, 2018.

Road map towards a harmonized pan-European surveillance of obesity-related lifestyle behaviours and their determinants in children and adolescents.

OBJECTIVES: To develop a road map towards a harmonized pan-European surveillance system for children and adolescents. METHODS: Representatives of five European surveillance systems and the German Health Interview and Examination Survey for Children and Adolescents contributed to the road map through a structured workshop in 2016. RESULTS: A conceptual framework for this road map was developed with seven action points (APs) guiding the successive cross-country harmonization. First, key indicators of health behaviour and their determinants in children and adolescents will be identified (AP1, 2); short screening instruments will be developed and implemented to assess and monitor key indicators (AP3, 4). In parallel, optional supplementary modules could be implemented to provide objective data (AP5). This would allow mutual calibration and improvement of existing instruments before their progressive replacement by more comparable measurement tools (AP6). The establishment of a competence platform is envisaged for guiding the harmonization process (AP7). CONCLUSIONS: This approach builds on existing systems, provides comparable key health indicators across European regions, helps to assess temporal trends and-once in place-will facilitate health reporting and monitoring of national and international health targets.

Sleep duration and blood pressure in children: Analysis of the pan-European IDEFICS cohort.

The present study aims to examine the cross-sectional and longitudinal association between self-reported nocturnal sleep duration, blood pressure, and hypertension in European children, aged 2-9.9 years, participating in the IDEFICS project. Blood pressure (BP) and the main anthropometric indices were measured according to standardized procedures. Childhood elevated BP and hypertension were defined according to the European Society of Hypertension Guidelines for children and adolescents. Parents reported lifestyle and socio-demographic data. Nocturnal sleep duration was assessed as part of a parental 24-h recall and categorized as follows: (a) ≤9 hours/night; (b) >9 hours to ≤10 hours/night; (c) >10 hours to ≤11 hours/night; and (d) >11 hours/night. A complete set of variables included in the present analysis was provided by 7974 participants (boys/girls = 4049/3925) at the baseline survey (T0). Of them, 5656 were re-examined 2 years later at follow-up (T1). Children reporting shorter sleep duration at T0 had significantly higher BP values (P for trend < 0.001) compared to those who slept more. Prospective analyses showed that shorter sleep duration at baseline predicted, over the 2-year follow-up, higher increases in systolic blood pressure and diastolic blood pressure, after adjustment for age, sex, country of origin, BMI z-score, parental education, physical activity, screen time, and T0 value of the examined outcome variables (P for trend < 0.001). Our findings reveal that shorter sleep duration is associated with higher BP in childhood, suggesting that sleep may be a potential risk factor for hypertension later in life.

Cross-sectional and longitudinal associations between psychosocial well-being and sleep in European children and adolescents.

Research on associations of positive mental health, in contrast to mental ill-health, with sleep duration and sleep disturbances in young populations is scarce. In particular, longitudinal studies focussing on the influence of positive mental health on sleep characteristics are lacking. Therefore, we investigated cross-sectional and longitudinal associations of psychosocial well-being with sleep duration and sleep disturbances. For the cross-sectional analysis, we used data of 3-15-year-old children and adolescents participating in the 2013/14 examination of the European IDEFICS/I.Family cohort study (N = 6,336). The longitudinal analysis was restricted to children who also participated in the 2009/10 examination (N = 3,379). Associations between a psychosocial well-being score created from 16 items of the KINDLR Health-Related Quality of Life Questionnaire covering emotional well-being, self-esteem and social relationships, an age-standardized nocturnal sleep duration z-score and two sleep disturbance indicators ("trouble getting up in the morning", "difficulties falling asleep") were estimated using linear and logistic mixed-effects models. Cross-sectionally, a higher well-being score was associated with longer sleep duration and lower odds of sleep disturbances. A positive change in the well-being score over the 4-year period was associated with longer sleep duration and lower odds of sleep disturbances at follow-up. However, there was only weak evidence that higher psychosocial well-being at baseline was associated with better sleep 4 years later. Thus, our results suggest that increases in well-being are associated with improvements in both sleep duration and sleep disturbances, but that well-being measured at one point in time does not predict sleep characteristics several years later.

Disordered eating in three different age groups in Cyprus: a comparative cross-sectional study.

OBJECTIVE: The objective of this study was to evaluate disordered eating behaviours (DEBs) in different age groups in a Cypriot non-clinical population sample. STUDY DESIGN: Comparative cross-sectional study. METHOD: A total of 1716 participants from the Cyprus component of the I.Family study completed the Eating Attitudes Test-26 (EAT-26). The EAT-26 score ≥20 was used to define participants at risk for DEBs. Participants were divided according to age: adolescence (12-18 years old), young adulthood (25-45 years old) and middle adulthood (46-60 years old). RESULTS: Mean EAT-26 total scores were higher for middle adulthood men and women compared with the two younger age groups. Young adulthood women had the highest percentage of behavioural symptoms of DEBs: binge eating (35%) and laxatives/diet pills/diuretics (12%) compared with the other age groups. Men and women in young adulthood had the highest percentage of participants with EAT-26 scores ≥20. In logistic regression analysis, age group did not prove a significant predictor of DEB risk in a model adjusting for sex, body mass index and physical activity. CONCLUSION: DEB can present at any age and was not confined to adolescence.

Children's stress-related reports and stress biomarkers interact in their association with metabolic syndrome risk.

The purpose was to examine the cross-sectional associations of stress-related reports and stress biomarkers with metabolic syndrome (MetS) risk in children while also testing the interaction between stress biomarkers and stress reports. In 353 children (5-10 years old, 7.9% overweight/obese), MetS risk was measured by blood pressure, waist circumference, glucose homeostasis, triglycerides, and high-density cholesterol. Stress was measured by stress-related reports (events, emotions, and internalizing/externalizing problems) and two biomarkers: salivary cortisol (total-day and morning output) and heart rate variability (percentage of consecutive normal RR intervals differing more than 50 ms and low-to-high-frequency ratio). Cross-sectional regression analyses with z scored total MetS risk as outcome were adjusted for age, sex, and socio-economic status. Only internalizing problems were directly related to a higher MetS risk score (ß = 0.236). Cortisol and heart rate variability were significant moderators: High cortisol morning output resulted in a positive (unfavourable) report-MetS relationship (ß = 0.259-0.552), whereas low percentage of consecutive normal RR intervals differing more than 50 ms resulted in a negative (favourable) report-MetS relationship (ß = -0.298) and low low-to-high-frequency ratio in a positive (unfavourable) report-MetS relationship (ß = 0.478). In conclusion, stress can sometimes be a disadvantageous factor in metabolic health of otherwise healthy children. The cortisol biomarker seems relevant because metabolic risk was highest when stress-related reports were accompanied by high morning cortisol output.

Bidirectional associations between psychosocial well-being and adherence to healthy dietary guidelines in European children: prospective findings from the IDEFICS study.

BACKGROUND: In children the relationship between a healthy diet and psychosocial well-being has not been fully explored and the existing evidence is inconsistent. This study investigates the chronology of the association between children's adherence to healthy dietary guidelines and their well-being, with special attention to the influence of weight status on the association. METHODS: Seven thousand six hundred seventy five children 2 to 9 years old from the eight-country cohort study IDEFICS were investigated. They were first examined between September 2007 and June 2008 and re-examined again 2 years later. Psychosocial well-being was measured using self-esteem and parent relations questions from the KINDL® and emotional and peer problems from the Strengths and Difficulties Questionnaire. A Healthy Dietary Adherence Score (HDAS) was calculated from a 43-item food frequency questionnaire as a measure of the degree to which children's dietary intake follows nutrition guidelines. The analysis employed multilevel logistic regression (country as random effect) with bidirectional modeling of dichotomous dietary and well-being variables as both exposures and outcomes while controlling for respective baseline values. RESULTS: A higher HDAS at baseline was associated with better self-esteem (OR 1.2, 95% CI 1.0;1.4) and fewer emotional and peer problems (OR 1.2, 95% CI 1.1;1.3 and OR 1.3, 95% CI 1.2;1.4) 2 years later. For the reversed direction, better self-esteem was associated with higher HDAS 2 years later (OR 1.1 95% CI 1.0;1.29). The analysis stratified by weight status revealed that the associations between higher HDAS at baseline and better well-being at follow-up were similar in both normal weight and overweight children. CONCLUSION: Present findings suggest a bidirectional relation between diet quality and self-esteem. Additionally, higher adherence to healthy dietary guidelines at baseline was associated with fewer emotional and peer problems at follow-up, independent of children's weight status.

Associations between social vulnerabilities and psychosocial problems in European children. Results from the IDEFICS study.

The effect of socioeconomic inequalities on children's mental health remains unclear. This study aims to explore the cross-sectional and longitudinal associations between social vulnerabilities and psychosocial problems, and the association between accumulation of vulnerabilities and psychosocial problems. 5987 children aged 2-9 years from eight European countries were assessed at baseline and 2-year follow-up. Two different instruments were employed to assess children's psychosocial problems: the KINDL (Questionnaire for Measuring Health-Related Quality of Life in Children and Adolescents) was used to evaluate children's well-being and the Strengths and Difficulties Questionnaire (SDQ) was used to evaluate children's internalising problems. Vulnerable groups were defined as follows: children whose parents had minimal social networks, children from non-traditional families, children of migrant origin or children with unemployed parents. Logistic mixed-effects models were used to assess the associations between social vulnerabilities and psychosocial problems. After adjusting for classical socioeconomic and lifestyle indicators, children whose parents had minimal social networks were at greater risk of presenting internalising problems at baseline and follow-up (OR 1.53, 99% CI 1.11-2.11). The highest risk for psychosocial problems was found in children whose status changed from traditional families at T0 to non-traditional families at T1 (OR 1.60, 99% CI 1.07-2.39) and whose parents had minimal social networks at both time points (OR 1.97, 99% CI 1.26-3.08). Children with one or more vulnerabilities accumulated were at a higher risk of developing psychosocial problems at baseline and follow-up. Therefore, policy makers should implement measures to strengthen the social support for parents with a minimal social network.

Inventory of surveillance systems assessing dietary, physical activity and sedentary behaviours in Europe: a DEDIPAC study.

Background: There is a need for harmonized public health surveillance systems to monitor regional variations and temporal trends of health behaviours and health outcomes and to align policies, action plans and recommendations in terms of healthy diet and physical (in)activity within Europe. We provide an inventory of currently existing surveillance systems assessing diet, physical activity, and sedentary behaviours in Europe as a tool to assist in the identification of gaps and needs and to contribute to the roadmap for an integrated pan-European surveillance system. Methods: An inventory questionnaire was completed by representatives of eleven European countries. Eligible surveillance systems were required to meet specific inclusion criteria. First, pre-screening of available surveillance systems in each country was conducted. Second, an in-depth appraisal of the retained surveillance systems complying with the pre-defined requirements was performed. Results: Fifty surveillance systems met the inclusion criteria: six multinational European surveys and forty-four national surveys. Dietary intake and physical activity are the domains predominantly assessed and adults are the most frequently studied age group. Conclusions: Many on-going activities were identified at the national level focussing on adults, but fewer surveillance systems involving vulnerable groups such as infants and pre-school children. Assessment of sedentary and dietary behaviours should be more frequently considered. There is a need for harmonization of surveillance methodologies, indicators and target populations for between-country and over time comparisons. This inventory will serve to feed future discussions within the DEDIPAC-JPI major framework on how to optimize design and identify priorities within surveillance.

Bidirectional associations between psychosocial well-being and body mass index in European children: longitudinal findings from the IDEFICS study.

BACKGROUND: The negative impact of childhood overweight on psychosocial well-being has been demonstrated in a number of studies. There is also evidence that psychosocial well-being may influence future overweight. We examined the bidirectional association between childhood overweight and psychosocial well-being in children from a large European cohort. The dual aim was to investigate the chronology of associations between overweight and psychosocial health indicators and the extent to which these associations may be explained by parental education. METHODS: Participants from the IDEFICS study were recruited from eight countries between September 2007 and June 2008 when the children were aged 2 to 9.9 years old. Children and families provided data on lifestyle, psychosocial well-being, and measured anthropometry at baseline and at follow-up 2 years later. This study includes children with weight, height, and psychosocial well-being measurements at both time points (n = 7,831). Psychosocial well-being was measured by the KINDL® and Strengths and Difficulties Questionnaire respectively. The first instrument measures health-related quality of life including emotional well-being, self-esteem, parent relations and social relations while the second measures well-being based on emotional symptoms, conduct problems and peer-related problems. Logistic regression was used for modeling longitudinal associations. RESULTS: Children who were overweight at baseline had increased risk of poor health-related quality of life (odds ratio (OR) = 1.23; 95 % confidence interval (CI):1.03-1.48) measured 2 years later; this association was unidirectional. In contrast to health-related quality of life, poor well-being at baseline was associated with increased risk of overweight (OR = 1.39; 95 % CI:1.03-1.86) at 2 year follow-up; this association was also only observed in one direction. Adjustment for parental education did not change our findings. CONCLUSION: Our findings indicate that the association between overweight and psychosocial well-being may be bidirectional but varies by assessment measures. Future research should further investigate which aspects of psychosocial well-being are most likely to precede overweight and which are more likely to be consequences of overweight.

Primary school students' mental health in Uganda and its association with school violence, connectedness, and school characteristics: a cross-sectional study.

BACKGROUND: Few studies have explored risk factors for poor mental health in Ugandan primary schools. This study investigated whether individual- and contextual-level school-related factors including violence from school staff and other students, connectedness to school and peers, as well as school size and urban/rural location, were associated with mental health difficulties in Ugandan children. We also examined whether associations between violence exposure at school and mental health were mediated by connectedness as well as whether associations were different for boys and girls. METHODS: The analytic sample consisted of 3,565 students from 42 primary schools participating in the Good Schools Study. Data were collected through individual interviews conducted in June and July 2012. Mental health was measured using the Strengths and Difficulties Questionnaire. Multilevel logistic regression was applied to investigate factors associated with mental health difficulties. RESULTS: Experiences of violence from school staff and other students in the past week were strongly associated with mental health difficulties (OR = 1.58, 95 % CI 1.31 to 1.90 and 1.81, 1.47 to 2.23, respectively). Children with a low school connectedness had 1.43 times (1.11 to 1.83) the odds of mental health difficulties compared to those with a high school connectedness. The OR comparing children never feeling close to other students at their school with those always feeling close was 1.86 (1.18 to 2.93). The effect of violence on mental health was not mediated through the connectedness variables. School size was not related to mental health difficulties, but attending an urban school increased the odds of mental health difficulties after accounting for other factors. We did not find evidence that the effect of one or more of the exposures on the outcome differed between boys and girls. CONCLUSIONS: These findings suggest that violence in school and low connectedness to school and peers are independently associated with mental health difficulties and interventions should address both concurrently. Extra support may be needed for students in urban schools. TRIAL REGISTRATION: Clinicaltrials.gov NCT01678846 . Registered 24 August 2012.