External Publications Using GUI Data

Background
Preventing child mental health problems and child obesity have been recognized as public health priorities. The aim of the present study was to examine whether being breastfed (at all or exclusively) in infancy was a predictor of mental well-being and protective against risk of obesity at age 9.

Methods
Cross-sectional data from a large, nationally representative cohort study in the Republic of Ireland was used (n = 8357). Data on breastfeeding were retrospectively recalled. Child mental well-being was assessed using a parent-completed Strengths and Difficulties Questionnaire (SDQ). Child’s height and weight were measured using scientifically calibrated instruments.

Results
Logistic regression analyses indicated that, after controlling for a wide range of potential confounding variables, being breastfed in infancy was associated with a 26% (P < 0.05) reduction in the risk of an abnormal SDQ score at 9 years. Being breastfed remained a significant predictor of child mental well-being when child obesity was controlled for, indicating that being breastfed, independent of child obesity, is a predictor of child mental well-being. The results of a second logistic regression indicated that, after controlling for a wide range of potential confounding variables, being breastfed for between 11 and 25 weeks was associated with a 36% (P < 0.05) reduction in the risk of obesity at 9 years, while being breastfed for 26 weeks or longer was associated with a 48% (P < 0.01) reduction in the risk of obesity at 9 years.

Conclusions
Breastfeeding in infancy may protect against both poor mental well-being and obesity in childhood.

Background
Psychotic experiences (PEs) are commonly reported in adolescence and are associated with a range of negative outcomes. Few targets for intervention for PEs have been identified. One potential target is self-concept: an individual’s beliefs about his/her personal attributes. Improvements in self-concept have been shown to reduce psychotic symptoms in patients with schizophrenia but no study has investigated the relationship between changes in self-concept and risk of PEs in the general population.

We aimed to investigate: (a) the relationship between child and adolescent self-concept and adolescent PEs; and (b) whether changes in self-concept between childhood and adolescence were associated with risk of adolescent PEs.

Method
Using data from age 9 and age 13 (n = 7,423) of the child cohort (Cohort’98) from the Growing Up in Ireland study we investigated the relationship between self-concept at age 9 and age 13 and PEs at age 13. PEs were measured using the Adolescent Psychotic Symptoms Screener and self-concept was measured using the Piers Harris-II. Using a stratified analysis, we investigated the relationship between change in self-concept between age 9 and age 13 and the risk of PEs at age 13. Additionally we investigated changes across the six self-concept subscales.

Results
Psychotic experiences were reported by 13% of participants at age 13. ‘Very low’ self-concept at age 9 was associated with an increased risk of PEs at age 13 (Adjusted-OR: 2.74, CI: 1.80–4.19), and ‘High’ self-concept at age 9 was associated with a decreased risk of PEs at age 13 (Adjusted-OR: 0.77, CI: 0.60–0.97). The stratified analysis indicated that improvements in self-concept reduced the odds of adolescent PEs and decline in self-concept increased the odds of adolescent PEs. This effect was noted across the majority of the self-concept subscales.

Conclusions
There is a strong relationship between self-concept and PEs. The antecedents of low self-concept may be a useful target for preventative psychiatry. Broad-spectrum interventions targeting self-concept in childhood may help to reduce the incidence of PEs in adolescence

Background
Public health policies attempt to increase parental identification of child overweight and obesity. The objective of the present research was to determine the cross-sectional, prospective and longitudinal associations between parental identification of child overweight and child mental health problems.

Methods
We made use of two cohort studies of Australian (Longitudinal Study of Australian Children, LSAC) and Irish children (Growing up in Ireland Study, GUI) that measured parental identification of child overweight and child mental health problems. Participant included 6502 (LSAC) and 7503 (GUI) children (49% female) and their parents. Child mental health problems were measured using child, parent and teacher-reported Strengths and Difficulties Questionnaires (SDQ) at ages 9/10 years old to 12/13 years old. In all analyses we controlled for child Z-BMI.

Results
In LSAC children whose parents identified them as being overweight at age 10 experienced worse mental health at age 10 (β = 0.21, SE = 0.04) and age 12 (β = 0.13, SE = 0.04) than children whose parents failed to identify them as overweight. In GUI children whose parents identified them as being overweight at age 9 experienced worse mental health at age 9 (β = 0.20, SE = 0.04) and age 13 (β = 0.22, SE = 0.04). In LSAC parental identification of child overweight at age 10 did not significantly predict changes in mental health problems from age 10 to 12 (β = −0.02, SE = 0.03). In GUI parental identification of child overweight was predictive of increases in mental health problems from age 9 to 13 (β = 0.08, SE = 0.03).

Conclusions
Parental identification of child overweight and obesity is associated with worse child mental health, independent of child body weight. Parents should be aware of the potential stigma and mental health difficulties associated with labelling a child as overweight.

Background
Research has demonstrated positive associations between adverse childhood experiences (ACEs) and substance use behaviours in young adults. However, many of these are based on cross-sectional data. The pathway between ACEs and substance misuse among emerging adults is also not fully understood and few studies have investigated potential mediating factors.

Methods
We analysed data from the Child Cohort of the Growing Up in Ireland study, a nationally representative longitudinal sample of children recruited at 9 years of age (n = 4,729). Logistic regression was used to examine individual and cumulative ACE exposure relationships with substance use at age 20 years. Mediation analyses were used to assess whether parental and peer relationships and school engagement mediate ACE history associations with substance use behaviours.

Results
ACE exposure relationships with current cannabis use, other illicit drug use and problematic drug use were observed. In particular, young adults who had experienced 2 ACEs or 3 + ACEs had an approximate two-fold (OR=1.80, 95 % CI: 1.29, 2.51) and approximate three-fold (OR=2.94, 95 % CI: 2.06, 4.19) increased odds of problematic drug use, respectively, when compared to participants who had experienced no ACEs during the study period. Mediation analyses suggested that parent and peer attachment and liking school partially mediate relationships between ACEs and substance use behaviours.

Conclusions
Children who have experienced ACEs are at higher risk of future substance use and problematic drug use. In supporting these children, identified mediators such as interpersonal relationships and school engagement may help guide selection of prevention interventions.

Background
Self-harm is a major public health concern in young people and is governed by a complex interaction of different risk factors. While many studies have identified these risk factors, less is known about how they tend to co-occur together.

Methods
A latent class analysis was conducted using risk factors for self-harm from two waves at ages 13 and 17 from the Growing Up in Ireland (GUI) study their associations with self-harm were examined longitudinally at ages 17 and 20, respectively.

Results
At age 13, there was a ‘peer problems’ group with higher probabilities of bullying, being unpopular and internalising problems and a ‘school and substance use problems’ group with higher probabilities of substance use, truancy or excessive absence from school and violence. Both of these two groups had over a two-fold risk of self-harm at age 17 in comparison to the low risk factor group. At age 17, there was a group with depression that was diagnosed by a medical professional with the highest relative risk (RR:13.9 (95 % CI 10.2–19.0)) of self-harm at age 20. Two other groups with undiagnosed depression had high probabilities of being bullied, and either high or low probabilities of substance use that had a 9.4 (95 % CI 6.8–13.1) and 7.4 (95 % CI 5.5–10.0) relative risk of self-harm at age 20, respectively.

Conclusions
Identifying hidden sub-groups using risk factors for self-harm in young people can inform potential public health interventions by clinicians and other professionals who work with young people.

Background
Social inequalities in the prevalence of childhood overweight and obesity are well-established, but less is known about when the social gradient first emerges and how it evolves across childhood and adolescence.

Objective
This study examines maternal education differentials in children’s body mass trajectories in infancy, childhood and adolescence using data from four contemporary European child cohorts.

Methods
Prospective data on children’s body mass index (BMI) were obtained from four cohort studies—Generation XXI (G21—Portugal), Growing Up in Ireland (GUI) infant and child cohorts, and the Millennium Cohort Study (MCS—UK)—involving a total sample of 41,399 children and 120,140 observations. Children’s BMI trajectories were modelled by maternal education level using mixed-effect models.

Results
Maternal educational inequalities in children’s BMI were evident as early as three years of age. Children from lower maternal educational backgrounds were characterised by accelerated BMI growth, and the extent of the disparity was such that boys from primary-educated backgrounds measured 0.42 kg/m2 (95% CI 0.24, 0.60) heavier at 7 years of age in G21, 0.90 kg/m2(95% CI 0.60, 1.19) heavier at 13 years of age in GUI and 0.75 kg/m2 (95% CI 0.52, 0.97) heavier in MCS at 14 years of age. The corresponding figures for girls were 0.71 kg/m2 (95% CI 0.50, 0.91), 1.31 kg/m2 (95% CI 1.00, 1.62) and 0.76 kg/m2 (95% CI 0.53, 1.00) in G21, GUI and MCS, respectively.

Conclusions
Maternal education is a strong predictor of BMI across European nations. Socio-economic differentials emerge early and widen across childhood, highlighting the need for early intervention.

Background
Taking oral antibiotics during childhood has been linked with an increased risk of childhood obesity. This study assessed any potential association in number of courses of antibiotics taken between 2–3 and 4–5 years of age and body mass trajectory up to age 5.

Methods
The study was a secondary analysis of 8186 children and their parents from the infant cohort of the Irish National Longitudinal Study of Children. Antibiotic use was measured by parental recall between ages 2–3 and 4–5. Longitudinal models described the relationship between antibiotic exposure and body mass index (BMI) standard deviation scores and binary outcomes, and examined interactions between covariates, which included socioeconomic status, diet assessed by food frequency questionnaires and maternal BMI.

Results
Any antibiotic usage between 2 and 3 years did not predict risk of overweight or obesity at age 5. Four or more courses of antibiotics between 2 and 3 years were independently associated with obesity at age 5 (odds ratio 1.6, 95% confidence interval 1.11–2.31). Effect size was modest (coefficient + 0.09 body mass SD units, standard error 0.04, P = 0.037). Maternal BMI modified the relationship: ≥ 4 courses of antibiotics between 2 and 3 years were associated with a + 0.12 body mass SD units increase in weight at age 5 among children of normal-weight mothers (P = 0.035), but not in children of overweight mothers.

Conclusions
Number of antibiotic courses, rather than antibiotic use, may be an important factor in any link between early antibiotic exposure and subsequent childhood obesity. Research is needed to confirm differential effects on babies of normal versus overweight/obese mothers independent of socioeconomic factors.

Background
The aim of this study was to use a social-ecological approach to examine the influence of individual, social, and environmental factors on moderate-to-vigorous physical activity (MVPA) and screen-time in a sample of 9-year-old children in Ireland.

Methods
The sample was 1509 boys and girls from the Growing Up in Ireland (GUI) national study. MVPA, screen time, and individual, social, and environmental variables were assessed via questionnaires completed by children, their parents, and their teachers. Multiple regression was used to identify factors that correlated with children’s MVPA and screen-time levels.

Results
For boys, factors such as activity with friends (P < .0001) and popularity (P < .01) were associated with MVPA, while factors such as BMI (P < .01) and MVPA (P < .01) were associated with screen time. Similarly for girls, factors such as activity with friends (P < .0001) and sociability were associated with MVPA, however factors such as BMI (P < .05), and access to play space (P < .05) were more closely associated with screen time.

Conclusion
Social factors were more closely associated with MVPA, while individual factors were significantly correlated with screen time for both boys and girls. Correlates differed for boys and girls, suggesting that interventions should consider both the target population as well as the activity behavior.

Background
The association between multidimensional household poverty (MHP) and child and mother psychopathology trajectories is not well understood. The aim of this paper is to explore this association.

Methods
We analysed 9241 infants and mothers recruited at 9-months (m) and 32-years (y) respectively from the Growing-up-in-Ireland study and followed up when the child was aged 3, 5, 7, 9 and 13y. MHP was derived from monetary, subjective and material poverty questionnaires completed by mothers before infant age 3y using latent-class-analysis. Confounder-adjusted linear spline multilevel models were used to examine the association between MHP before 3y and trajectories of child (3-to-13y) and mother (34-to-46y) psychopathology wellbeing measures (Strengths-and-difficulties-questionnaire and Centre-for-epidemiological-studies-depression-scale, respectively).

Results
In adjusted models, MHP before 3y was associated with a higher mean difference(MD) (MD:0.67, 95%CI 0.41,0.92) in child psychopathology at 3y and this was broadly similar at age 13y (MD:0.87, 95% CI 0.57,1.17). MHP prior to 3y was associated with a higher mother psychopathology when her child was age 3y (MD:1.07, 95% CI 0.90,1.23) and this persisted albeit with a slight reduction in magnitude at age 13y of the child (MD:0.72, 95% CI 0.53,0.90).

Conclusions
Though replication in other cohorts is required, findings suggest that MHP exposure in child infancy may have early negative life course impacts on mother and child wellbeing that persist for up to a decade. If causal, these findings underscore the importance of early life course policy interventions to prevent and ameliorate poverty to reduce long term psychopathology of mothers and their children.

Background
The Covid pandemic arrived in Ireland on February 29, 2020. In the following weeks various restrictions were introduced to stem the spread of the disease. Anxiety over the spread of the disease and over the restrictions introduced had an adverse effect upon mental health. This study examines the change in mental health for two groups: young adults aged around 23 at the time of onset of Covid (the 1998 cohort) and a sample of principal carers (PCs) of children who were aged 13 at the onset of Covid (the 2008 cohort).

Methods
Data were obtained from the two cohorts of the longitudinal Growing Up In Ireland (GUI) survey. The sample included 1953 young adults (from the 1998 cohort) and 3547 principal carers (from the 2008 cohort). Mental health as measured by the Centre for Epidemiological Studies Depression—8 scale was obtained for the last pre-Covid wave and for the Covid wave (surveyed in December 2020). Observations for which CES-D8 was not available in either pre or post Covid waves were excluded. Post-Covid sampling weights were applied. The change in depression rates was decomposed into a growth and distribution effect using a Shapley decomposition. The socioeconomic gradient of CES-D8 was examined pre and post Covid using concentration indices and a transition matrix was constructed to examine the dynamics of changes in CES-D8 and depression pre and post-Covid.

Results
Relative to the last pre-Covid survey, mental health, as measured by CES-D8 deteriorated for both the young adults of the 1998 cohort and the PCs of the 2008 cohort. For young adults, the deterioration was more pronounced for females. There was no observable socioeconomic gradient for poor mental health amongst young adults, both pre and post Covid. For mothers from the 2008 cohort, a gradient was observed during the pre-COVID-19 pandemic period with poorer mental health status for lower-income and less educated mothers. This gradient was less pronounced post-Covid, the levelling-off arising from a greater deterioration in mental health for higher-income and better-educated PCs.

Conclusion
Both observed cohorts showed a significant deterioration in mental health post Covid. For young adults the effect was significantly more pronounced among females and this is consistent with generally poorer mental health amongst females in this age group. There was little or no socioeconomic gradient observed for young adults, but the gradient became more shallow for principal carers. Care must be taken in terms of drawing policy implications from this study as the Covid-19 pandemic was arguably a unique event, even allowing for the likelihood of future pandemics. However, the study highlights the vulnerability of young adults, especially females, to the mental health effects arising from major public health shocks.

Background
The COVID-19 pandemic has been dubbed the “biggest public health crisis since the Second World War”. In Ireland, schools were closed for 141 days, dramatically altering the day to day lives of children in Ireland. This research aimed to evaluate the overall wellbeing of schoolchildren in Ireland and capture the prevalence and factors contributing to poor mental health.

Methods
A cross-sectional study was performed based on data from the Growing Up in Ireland COVID-19 web survey of the ’08 Infant cohort. Mental Health Inventory-5 scores were used to assess children at risk of mental health disorders. Logistic regression examined associations between various demographic and psychosocial factors and risk of mental health disorders.

Results
This study included 2,867 primary caregiver- child dyads. Almost 25% of 12/13-year-olds were at risk of mental health disorders (MHDs). An adjusted logistic regression model found associations between being at higher risk of MHDs and factors such as reduced physical activity levels (OR 1.35, 95% CI 1.10-1.66), spending less time outdoors (OR 1.48, 95% CI 1.18-1.85), increased screen-time (OR 1.35, 95% CI 1.09-1.67) and increased arguments with PCGs (OR 3.44, 95% CI 2.78-4.27). Having a trusted adult confidante reduced the risk of MHD (OR 0.25, 95% CI 0.14-0.45).

Conclusions
The prevalence of 12/13-year olds at elevated risk of MHD was high, indicating an urgent need for enhancement of child and adolescent mental health services in Ireland. Physical activity, time outdoors and supportive relationships with primary caregivers were positively associated with reduced MHD risk.

Key messages

• Children were impacted by the COVID-19 restriction measures in a way that was disproportionate to their risk.
• To reduce the risk of poor mental health outcomes for a generation of “quarantweens” we need to place children front-andcentre of our response as we recover from COVID-19.

Background
The gold standard for categorisation of weight status is clinically measured body mass index (BMI), but this is often not practical in large epidemiological studies.

Objectives
To determine if a child’s weight perception or a mother’s perception of a child’s weight status is a viable alternative to measured height and weight in determining BMI classification. Secondary outcomes are to determine the influence of a mother’s BMI on her ability to categorise the child’s BMI and a child’s ability to recognise his/her own BMI.

Methods
Cross-sectional analysis of the growing up in Ireland cohort study, a nationally representative cohort of 8568 9-year-old children. The variables considered for this analysis are the child’s gender, BMI (International Obesity Taskforce grade derived from measured height and weight) and self-perceived weight status, and the mother’s weight perception of the child, BMI (derived from measured height and weight) and self-perceived weight status. Cohen’s weighted-kappa was used to evaluate the strength of the agreement between pairwise combinations of the BMI variables. Cumulative and adjacent categories logistic regression were used to predict how likely a person rates themselves as under, normal or overweight, based on explanatory variables.

Results
Mothers are more accurate at correctly classifying their child’s BMI (κ=0.5; confidence intervals (CI) 0.38–0.51) than the children themselves (κ=0.25; CI 0.23–0.26). Overweight mothers are better raters of their child’s BMI (κ=0.51; CI 0.49–0.54), compared with normal (κ=0.44; CI 0.41–0.47) or underweight mothers (κ=0.4; CI 0.22–0.58), regardless of whether the mother’s BMI is derived from measured height and weight or self-perceived. The mother’s perception of the child’s weight status is not an influencing factor on the child’s ability to correctly classify him/herself, but the child’s self-perceived weight status influences the mother’s ability to correctly classify the child.

Conclusions
A mother’s BMI classification of her child is a viable alternative to BMI measurement in large epidemiological studies.

Background
The incidence and prevalence of childhood chronic disease is increasing worldwide. Obesity, poor diet and lifestyle may be more prevalent in children with a chronic disease than in their healthier contemporaries. The Growing Up in Ireland (GUI) study is a nationally representative cohort study of children living in the Republic of Ireland. The study has collected information from 8568 9-year-old Irish children on their experiences within their families, childcare settings, schools and communities, and how these impact on all aspects of children’s development.

Aims
This study aims to establish the prevalence of parentally reported chronic disease in children in Ireland and to describe their diet and lifestyle.

Methods
This study analyzed data from the Growing Up in Ireland longitudinal child cohort study and compared the diet, lifestyle and prevalence of obesity in children with and without a parentally reported chronic disease.

Results
Overall, 954 parents in the sample (11.1%) reported that their child had a chronic illness and 43.4% of these children are hampered by it in their daily activities. Respiratory disorders were the commonest type of chronic disease (46%) reported. Children with a chronic illness were more likely to be overweight or obese (32.9% compared to 25.0% of those without a chronic illness, p < 0.001). Children with chronic illness were also found to have a poorer diet, take less exercise and experienced significantly more social isolation than their peers (all p < 0.05).

Conclusions
Public health measures to address diet and lifestyle choices need to be cognisant of the needs of children with chronic diseases and tailor activities offered to be inclusive of all children. Medical professionals having contact with children with chronic conditions need to remember to reinforce the importance of diet and lifestyle whenever possible and to explore with families solutions to barriers to making healthy diet and lifestyle choices.

Background
The use of dietary quality scores/indices to describe diet quality in children has increased in the past decade. However, to date, few studies have focused on the use of these scores on disease outcomes such as childhood obesity and most are developed from detailed dietary assessments. Therefore, the aims of this study were: firstly to construct a diet quality score (DQS) from a brief dietary assessment tool; secondly to examine the association between diet quality and childhood overweight or obesity; thirdly we also aim to examine the associations between individual DQS components and childhood overweight or obesity.

Methods
A secondary analysis of cross sectional data of a sample of 8,568 9-year-old children and their families as part of the Growing Up in Ireland (GUI) study. Subjects were drawn from a probability proportionate to size sampling of primary schools throughout Ireland over the school year 2007–2008. Height and weight were measured by trained researchers using standardised methods and BMI was classified using the International Obesity Taskforce cut-points. The DQS (un-weighted) was developed using a 20-item, parent reported, food frequency questionnaire of foods consumed over the past 24 h. Adjusted odds ratios for overweight and obesity were examined by DQS quintile, using the first quintile (highest diet quality) as the reference category.

Results
The prevalence of normal weight, overweight and obese was 75, 19 and 6 % respectively. DQS ranged from -5 to 25, higher scores indicated higher diet quality in the continuous score. In analyses adjusted for gender, parent’s education, physical activity and T.V. viewing, child obesity but not overweight was significantly associated with poor diet quality: OR of 1.56 (95 % CI 1.02 2.38) in the 5th compared to the 1st DQS quintile. Findings from individual food items were inconsistent.

Conclusions
The findings suggest that diet quality may be an important factor in childhood obesity. A simple DQS developed from a short dietary assessment tool is significantly associated with childhood obesity.

Background
There are few prospective studies of factors that mediate the association between exposure to adverse childhood experiences (ACEs) and obesity in adolescence. Our aim was to address this limitation.

Methods
We used prospective data from the Growing up in Ireland cohort study, with measurements at 9, 13, and 18 years old. The exposures were 14 adverse experiences before age 9. The main outcome was body mass index (BMI) at 18 years. Mediators were daily activity, diet quality, self-image and behavioural difficulties at 13 years.

Results
Among the 4561 adolescents in the final cohort, 77.2% experienced any adversity, 50.5% were female and 26.7% were overweight/obese at 18 years. BMI Z was higher at ages 9 (0.54 vs 0.43, p < 0.05, 95% CI of difference: −0.22, −0.01) and 13 years (0.50 vs 0.35, p < 0.05, 95% CI of difference: −0.25, −0.06), in those exposed to an ACE, compared to those unexposed. Structural equation models revealed that behavioural difficulties (β = 0.01; 95% CI: 0.007–0.018, p < 0.001) and self-concept (β = 0.0027; 95% CI: 0.0004–0.0050, p = 0.026) indirectly mediate the association between exposure to ACEs and BMI at 18 years.

Conclusions
The association between ACEs and BMI in adolescence is mediated by behavioural difficulties and self-concept.

Impact

• In a previous study, we found modest associations between exposure to a range of adverse childhood experiences and weight gain at 13 years of age.
• The strength of the association between adverse childhood experiences and weight gain was lower at 18 years of age compared to the association observed at 13 years and was no longer significant after controlling for confounding and including possible mediators.
• The association between adverse childhood experiences and BMI in adolescence is indirectly mediated by behavioural difficulties and self-concept.

Background
There are no early, accurate, scalable methods for identifying infants at high risk of poor cognitive outcomes in childhood. We aim to develop an explainable predictive model, using machine learning and population-based cohort data, for this purpose.

Methods
Data were from 8858 participants in the Growing Up in Ireland cohort, a nationally representative study of infants and their primary caregivers (PCGs). Maternal, infant, and socioeconomic characteristics were collected at 9-months and cognitive ability measured at age 5 years. Data preprocessing, synthetic minority oversampling, and feature selection were performed prior to training a variety of machine learning models using ten-fold cross validated grid search to tune hyperparameters. Final models were tested on an unseen test set.

Results
A random forest (RF) model containing 15 participant-reported features in the first year of infant life, achieved an area under the receiver operating characteristic curve (AUROC) of 0.77 for predicting low cognitive ability at age 5. This model could detect 72% of infants with low cognitive ability, with a specificity of 66%.

Conclusions
Model performance would need to be improved before consideration as a population-level screening tool. However, this is a first step towards early, individual, risk stratification to allow targeted childhood screening.

Impact
• This study is among the first to investigate whether machine learning methods can be used at a population-level to predict which infants are at high risk of low cognitive ability in childhood.
• A random forest model using 15 features which could be easily collected in the perinatal period achieved an AUROC of 0.77 for predicting low cognitive ability.
• Improved predictive performance would be required to implement this model at a population level but this may be a first step towards early, individual, risk stratification.

Background
There is growing concern around youth mental health. A population health approach to improve mental health must address, among other issues, economic insecurity, access to housing and education, harm reduction from substance use. As a universal public health intervention, increasing physical activity at a population level may have an important role in our approach. The aim of this study was to examine the longitudinal association between physical activity patterns between childhood and early adolescence and emotional-behavioural difficulties in later adolescence.

Methods
This study was based on data from the ′98 Child cohort of the Growing Up in Ireland Study. Participants were categorized according to physical activity levels at ages 9 and 13. Emotional-behavioural difficulties at age 17 were measured using the parent-reported Strengths and Difficulties Questionnaire. Logistic regression was used to examine the association between physical activity and emotional-behavioural outcomes.

Results
Among 4618 participants included in the regression model, those categorized as Inactive (n=1607) or Reducer (n=1662) were more than twice as likely to have emotional-behavioural difficulties at age 17 compared with those who were Active [adjusted odds ratio (AOR) 2.1, 95% CI 1.46–3.01, P<0.001; AOR 1.93, 95% CI 1.34–2.76, P<0.001, respectively]. Among those with emotional-behavioural difficulties at baseline (n=525), those categorized as Active had 2.3-fold reduced odds for emotional-behavioural problems at age 17 compared with those who were Inactive (AOR 0.43, 95% CI 0.23–0.78, P=0.006).

Conclusions
Increasing physical activity among adolescents is a safe and sustainable public health intervention associated with improved mental health.

Background
There is limited knowledge of the extent of or factors underlying inequalities in uptake of childhood vaccination in Ireland. This paper aims to measure and decompose socioeconomic inequalities in childhood vaccination in the Republic of Ireland.

Methods
The analysis was performed using data from the first wave of the Growing Up in Ireland survey, a nationally representative survey of the carers of over 11,000 nine-month old babies collected in 2008 and 2009. Multivariate analysis was conducted to explore the child and parental factors, including socioeconomic factors that were associated with non-vaccination of children. A concentration index was calculated to measure inequality in childhood vaccination. Subsequent decomposition analysis identified key factors underpinning observed inequalities.

Results
Overall the results confirm a strong socioeconomic gradient in childhood vaccination in the Republic of Ireland. Concentration indices of vaccination (CI = −0.19) show a substantial pro-rich gradient. Results from the decomposition analysis suggest that a substantial proportion of the inequality is explained by household level variables such as socioeconomic status, household structure, income and entitlement to publicly funded care (29.9%, 24% 30.6% and 12.9% respectively). Substantial differences are also observed between children of Irish mothers and immigrant mothers from developing countries.

Conclusions
Vaccination was less likely in lower than in higher income households. Access to publicly funded services was an important factor in explaining inequalities.

Background
Unintended pregnancy is associated with increased risk for adverse neonatal and early childhood outcomes spanning an array of indicators, but it remains unclear whether these risks hold independent of other biological, social and environmental risk factors.

Methods
This study uses data from the first wave of the ‘Growing Up in Ireland Study’, a large nationally representative cohort study of more than 11 000 infants, to examine the risk factors associated with unintended pregnancy. Adopting a staged approach to the analysis, the study investigates whether pregnancy intention influences maternal health behaviours during pregnancy independent of background characteristics, and whether pregnancy intention carries any additional risk for adverse infant and maternal health outcomes when we adjust for background characteristics and prenatal behaviours.

Results
The study confirmed that sociodemographic factors are strongly associated with unintended pregnancy and that unintended pregnancy is associated with a range of health compromising behaviours that are known to be harmful to the developing fetus. While there was little evidence to suggest that pregnancy intention was associated with adverse neonatal outcomes or developmental delay independent of other covariates, there was strong evidence that intention status had a bearing on the mother’s psychosocial health. Unintended pregnancy was associated with increased risk of depression (risk ratio 1.36 [95% confidence interval 1.19, 1.54]), and higher parenting stress (risk ratio 1.27 [95% confidence interval 1.16, 1.38]).

Conclusions
Ascertaining the mother’s pregnancy intention during the first antenatal visit may represent a means for monitoring those at greatest risk for adverse mother and child outcomes.

Background
While it has been purported that excessive screen time can lead to behavioral problems, it has also been suggested that children with behavioral dysregulation receive more access to screens to manage problematic behavior. In this study, both temporally stable and longitudinal associations between screen time and externalizing and internalizing behaviors across childhood are examined to directly address this issue of directionality.

Methods
Data are from a prospective cohort of 10,172 Irish children, collected between 2010 and 2018 when children were ages 3, 5, 7, and 9. Children’s screen time (hours/day) and externalizing and internalizing behaviors (Strengths and Difficulties Questionnaire) were assessed via caregiver report. Random-intercepts cross-lagged panel models were used to estimate longitudinal bidirectional associations while controlling for temporally stable (i.e., ‘time-invariant’ or ‘trait-like’) differences between children.

Results
Temporally stable differences between children were observed for both screen time and behavior problems. Longitudinal trajectories for screen time lacked stability; however, and externalizing and internalizing behaviors stabilized increasingly during later childhood. Greater externalizing and internalizing behaviors at age 3 were directionally associated with increased screen time at age 5. Greater screen time at ages 3 and 5 was directionally associated with increased internalizing behaviors at ages 5 and 7, respectively. More screen time at age 7 was directionally associated with fewer internalizing behaviors at age 9. Screen time was not associated with later externalizing behaviors.

Conclusions
Bidirectional associations between screen time and internalizing behaviors were observed for preschoolers. Directional associations between screen time and internalizing difficulties were observed across childhood. These findings can inform screen use guidelines and family media planning at different ages and stages of development.