Relative Age and Attention-Deficit/Hyperactivity Disorder: Data From Three Epidemiological Cohorts and a Meta-analysis

Systematic review and meta-analysis: relative age in attention-deficit/ hyperactivity disorder and autism spectrum disorder

Youngest students in their class, with birthdates just before the school entry cut-off date, are overrepresented among children receiving an Attention-Deficit/Hyperactivity Disorder (ADHD) diagnosis or medication for this. This is known as the relative age effect. This systematic review and meta-analysis summarises the evidence on the influence of relative age on ADHD symptoms, diagnosis and medication prescribing. As no review to date has investigated the association with autism spectrum disorder (ASD) diagnosis, this is also examined. Following prospective registration with PROSPERO, we conducted a systematic review according to the PRISMA guidelines. We searched seven databases: Medline, Embase, PsycInfo, Web of Science Core Collection, ERIC, Psychology and Behavioural Sciences Collection, and Cochrane Library. Additional references were identified from manual search of retrieved reviews. We performed a meta-analysis of quantitative data. Thirty-two studies were included, thirty-one investigated ADHD and two ASD. Younger relative age was associated with ADHD diagnosis and medication, with relative risks of 1.38 (1.36-1.52 95% CI) and 1.28 (1.21-1.36 95% CI) respectively. However, risk estimates exhibited high heterogeneity. A relative age effect was observed for teacher ratings of ADHD symptoms but not for parent ratings. With regard to ASD, the youngest children in their school year were more likely to be diagnosed with ASD. This review confirms a relative age effect for ADHD diagnosis and prescribed ADHD medication and suggests that differences in teacher and parent ratings might contribute to this. Further research is needed on the possible association with ASD.

The impact of relative age effects on psychosocial development: A systematic review

BACKGROUND

Within the same school class, it is usual to find children who differ in age by almost a full calendar year. Although associations between being relatively young and poor academic outcomes are well documented, and relatively consistent, the associations between being relatively young and psychosocial outcomes are less clearly documented.

AIMS

To review research which presents data relating to associations between a child's relative age and their psychosocial development.

METHODS

A systematic review was conducted and reported in accordance with PRISMA guidelines.

RESULTS

Fifty-nine papers met the inclusion criteria. The outcomes of the narrative synthesis and three meta-analyses found consistent, but very small, associations with relative age indicating that those who are relatively young are more likely to have more negative behaviour, mental well-being, and social experiences.

CONCLUSIONS

Although being relatively young is associated with more negative psychosocial outcomes, the magnitude of these associations is consistently small. Furthermore, many of the outcome measures used are likely to be the result of multiple influences, not limited to the effects of relative age. Therefore, the findings are reassuring as they suggest that relative age itself is unlikely to substantially increase an individual's risk of poor psychosocial development.

Perspectives on ADHD in children and adolescents as a social construct amidst rising prevalence of diagnosis and medication use

The diagnosis of attention-deficit hyperactivity disorder (ADHD) is based on the presence of pervasive, persistent symptoms of inattention and/or hyperactivity/impulsivity typically emerging early in life and resulting in significant functional impairment. In contrast to a worldwide epidemiological prevalence of approximately 5% in children and 2-3% in adults, there are significant variations in the prevalence of administrative ADHD diagnoses and medication use. We assert that in order to explore the underlying dynamics of this phenomenon, a thorough understanding of the construct ADHD is necessary. We contend that ADHD is not a natural entity that unfolds within an individual and can be understood independent from societal and environmental factors, but rather that ADHD as a diagnosis can better be conceptualized as a valid and pragmatically useful social construct. Decisions to diagnose and treat ADHD should follow a person-centered approach and be focused on functional impairment within a socially constructed, context-dependent and environmentally contingent model.

Association between relative age at school and persistence of ADHD in prospective studies: an individual participant data meta-analysis

BACKGROUND

The youngest children in a school class are more likely than the oldest to be diagnosed with ADHD, but this relative age effect is less frequent in older than in younger school-grade children. However, no study has explored the association between relative age and the persistence of ADHD diagnosis at older ages. We aimed to quantify the association between relative age and persistence of ADHD at older ages.

METHODS

For this meta-analysis, we searched MEDLINE, Embase, CINAHL, PsycINFO, and PubPsych up to April 1, 2022, with terms related to "cohort" and "ADHD" with no date, publication type, or language restrictions. We gathered individual participant data from prospective cohorts that included at least ten children identified with ADHD before age 10 years. ADHD was defined by either a clinical diagnosis or symptoms exceeding clinical cutoffs. Relative age was recorded as the month of birth in relation to the school-entry cutoff date. Study authors were invited to share raw data or to apply a script to analyse data locally and generate anonymised results. Our outcome was ADHD status at a diagnostic reassessment, conducted at least 4 years after the initial assessment and after age 10 years. No information on sex, gender, or ethnicity was collected. We did a two-stage random-effects individual participant data meta-analysis to assess the association of relative age with persistence of ADHD at follow-up. This study was registered with PROSPERO, CRD42020212650.

FINDINGS

Of 33 119 studies generated by our search, we identified 130 eligible unique studies and were able to gather individual participant data from 57 prospective studies following up 6504 children with ADHD. After exclusion of 16 studies in regions with a flexible school entry system that did not allow confident linkage of birthdate to relative age, the primary analysis included 41 studies in 15 countries following up 4708 children for a period of 4 to 33 years. We found that younger relative age was not statistically significantly associated with ADHD persistence at follow-up (odds ratio 1·02, 95% CI 0·99-1·06; p=0·19). We observed statistically significant heterogeneity in our model (Q=75·82, p=0·0011, I2=45%). Participant-level sensitivity analyses showed similar results in cohorts with a robust relative age effect at baseline and when restricting to cohorts involving children with a clinical diagnosis of ADHD or with a follow-up duration of more than 10 years.

INTERPRETATION

The diagnosis of ADHD in younger children in a class is no more likely to be disconfirmed over time than that of older children in the class. One interpretation is that the relative age effect decreases the likelihood of children of older relative age receiving a diagnosis of ADHD, and another is that assigning a diagnostic label of ADHD leads to unexplored carryover effects of the initial diagnosis that persist over time. Future studies should be conducted to explore these interpretations further.

FUNDING

None.

Digital Cognitive Training for Children with Attention Deficit Hyperactivity Disorder

The present article used a pilot study to determine the effectiveness of digital cognitive mindfulness training developed based on dialectical behavioral therapy (DBT) in reducing attention deficit hyperactivity disorder (ADHD) symptoms in children. The sample consisted of 90 children (8-10 years old) diagnosed with ADHD. The participants were randomized into two groups: an experimental group (n = 45) and a control group (n = 45). Results were assessed at three time points: before, after the study, and one month after the end of the study. Regarding ADHD symptoms, the ANCOVA results showed that there were no statistically significant differences between the study groups for inattention and hyperactivity/impulsivity after testing. One month after completion of the program, there was a significant alleviation in symptoms of inattention, executive functioning, learning problems, aggression, and peer relationships. Hyperactivity was the only variable that showed a decrease both post-test and during follow-up. These results suggest that a DBT-based mindfulness program is a promising method of reducing ADHD symptoms in children.

A systematic meta-review of systematic reviews on attention deficit hyperactivity disorder

BACKGROUND

There are now hundreds of systematic reviews on attention deficit hyperactivity disorder (ADHD) of variable quality. To help navigate this literature, we have reviewed systematic reviews on any topic on ADHD.

METHODS

We searched MEDLINE, PubMed, PsycINFO, Cochrane Library, and Web of Science and performed quality assessment according to the Joanna Briggs Institute Manual for Evidence Synthesis. A total of 231 systematic reviews and meta-analyses met the eligibility criteria.

RESULTS

The prevalence of ADHD was 7.2% for children and adolescents and 2.5% for adults, though with major uncertainty due to methodological variation in the existing literature. There is evidence for both biological and social risk factors for ADHD, but this evidence is mostly correlational rather than causal due to confounding and reverse causality. There is strong evidence for the efficacy of pharmacological treatment on symptom reduction in the short-term, particularly for stimulants. However, there is limited evidence for the efficacy of pharmacotherapy in mitigating adverse life trajectories such as educational attainment, employment, substance abuse, injuries, suicides, crime, and comorbid mental and somatic conditions. Pharmacotherapy is linked with side effects like disturbed sleep, reduced appetite, and increased blood pressure, but less is known about potential adverse effects after long-term use. Evidence of the efficacy of nonpharmacological treatments is mixed.

CONCLUSIONS

Despite hundreds of systematic reviews on ADHD, key questions are still unanswered. Evidence gaps remain as to a more accurate prevalence of ADHD, whether documented risk factors are causal, the efficacy of nonpharmacological treatments on any outcomes, and pharmacotherapy in mitigating the adverse outcomes associated with ADHD.

The effect of Self-Regulation Based Cognitive Psychoeducation Program on emotion regulation and self-efficacy in children diagnosed with attention deficit hyperactivity disorder

AIM

This study aimed to determine the effect of Self-Regulation Based Cognitive Psychoeducation Program on emotion regulation and self-efficacy in children diagnosed with attention deficit hyperactivity disorder (ADHD) and receiving medication.

METHOD

The sample of this study with control group and pre-test, post-test and follow-up randomized experimental design consisted of children followed in the child and adolescent mental health outpatient clinic of a state hospital. The data were evaluated by parametric and non-parametric analyses.

RESULTS

A statistically significant increase was determined in the internal functional emotion regulation mean scores of children, who participated in the Self-Regulation Based Cognitive Psychoeducation Program, measured before, immediately after, and 6 months after the intervention (p < 0.05). A statistically significant increase was also found in their external functional emotion regulation mean scores measured before and 6 months after the intervention (p < 0.05). In addition, a statistically significant difference was found between their internal dysfunctional and external dysfunctional emotion regulation mean scores measured before and 6 months after the intervention; however the mean scores of those in the control group 6 months after the intervention were higher than those in the intervention group (p < 0.05). Furthermore, there was a statistically significant increase in their self-efficacy mean scores measured before and 6 months after the intervention (p < 0.05).

CONCLUSION

The Self-Regulation Based Cognitive Psychoeducation Program was found be effective in increasing the levels of emotion regulation and self-efficacy in children with ADHD.

The effect of school-entry age on health is understudied in low- and middle-income countries: A scoping review and future directions for research

Background

Substantive literature has assessed the impact of starting school at younger ages relative to peers on health in high-income countries (HICs), but there is little evidence from low- and middle-income countries (LMICs). Conclusions drawn from HICs may not apply to different education contexts and health threats. This study maps the empirical evidence on the effect of school-entry age on health in LMICs and identifies directions for future research.

Methods

We conducted a scoping review between August and September 2022 by systematically searching the health sciences, education, economics, psychology, and general sciences literature and included quantitative and qualitative studies. The exposure of interest was relative age for grade defined as starting or progressing through school at a younger or older age compared to peers who are in the same grade. We extracted key characteristics of included studies and summarized their findings. We categorized results into broad health domains which emerged a posteriori from our analyses of included studies, including neurodevelopment and mental health, sexual and reproductive health, non-communicable diseases, and nutrition.

Findings

We identified 8 studies from middle-income countries published between 2017 and 2022. Among those studies, we identified 3 quasi-experimental studies using data from Brazil, Mexico, and Vietnam, and 5 observational studies primarily from Türkiye. Children starting school earlier had an increased risk of being diagnosed with attention deficit hyperactivity disorder, earlier sexual debut and cohabitation, adolescent pregnancy, adolescent marriage, and engaged more frequently in risky behavior compared to children who started school later. Pregnant women who started school younger also had fewer prenatal care visits and experienced more pregnancy complications. Although most studies identified negative health consequences from starting school earlier, the evidence for nutritional outcomes, such as overweight and stunting, was mixed. No studies were identified from low-income countries.

Conclusions

Little is known about the health consequences of school-entry age in low-resource settings. Additional research is needed to investigate the impact of relative age for grade, whether and how these effects persist into adulthood, and to inform strategies that can offset potential disadvantages stemming from school-entry cut-off dates.

Children's Relative Age and Medicine Treatment for Attention-Deficit/Hyperactivity Disorder Across Australian Jurisdictions with Different School Enrolment Policies

Background: Children who are relatively young for their school grade are more likely to receive treatment for attention-deficit/hyperactivity disorder (ADHD). It is unclear whether the phenomenon also exists across Australia or is impacted by the school enrolment policy in place. Objective: We evaluated the association between children's relative age and initiation of ADHD medicines across Australian jurisdictions with different school enrolment policies and rates of delayed school entry. Methods: We used Australia-wide dispensing data for a 15% random sample of children 4-9 years of age in 2013-2017 to create a nationwide cohort. Due to high rates of delayed school entry in New South Wales (NSW), we used linked prescribing and education data for a cohort of NSW residents starting school in 2009 and 2012. We estimated incidence rate ratios (IRRs) for ADHD medicine across children's birth month, sex, and jurisdiction. We used asthma medicines as a negative control. Results: For girls, we observed a relative age effect in three out of five jurisdictions, with an IRR ranging from 1.3 to 2.8, comparing the youngest versus oldest birth month thirds. We observed more modest effects among boys, ranging from null to 1.5-fold. In NSW, the relatively youngest boys were less likely to initiate stimulant medicines than the oldest (IRR = 0.5, 95% confidence interval 0.29-0.78). We did not observe a relative age effect for initiation of asthma medicines. Conclusions: In jurisdictions with low rates of delayed entry, relatively young children were more likely to initiate ADHD medicines than their older classmates. We observed the inverse association in NSW where delayed entry was highest, likely reflecting the characteristics and needs of children who delay school entry for 1 year and become the oldest children in the grade. Increased awareness around children's maturity differences and school readiness may enhance appropriate diagnosis and treatment of ADHD.

Developmental Dyslexia: Disorder or Specialization in Exploration?

We raise the new possibility that people diagnosed with developmental dyslexia (DD) are specialized in explorative cognitive search, and rather than having a neurocognitive disorder, play an essential role in human adaptation. Most DD research has studied educational difficulties, with theories framing differences in neurocognitive processes as deficits. However, people with DD are also often proposed to have certain strengths - particularly in realms like discovery, invention, and creativity - that deficit-centered theories cannot explain. We investigate whether these strengths reflect an underlying explorative specialization. We re-examine experimental studies in psychology and neuroscience using the framework of cognitive search, whereby many psychological processes involve a trade-off between exploration and exploitation. We report evidence of an explorative bias in DD-associated cognitive strategies. High DD prevalence and an attendant explorative bias across multiple areas of cognition suggest the existence of explorative specialization. An evolutionary perspective explains the combination of findings and challenges the view that individuals with DD have a disorder. In cooperating groups, individual specialization is favored when features that confer fitness benefits are functionally incompatible. Evidence for search specialization suggests that, as with some other social organisms, humans mediate the exploration-exploitation trade-off by specializing in complementary strategies. The existence of a system of collective cognitive search that emerges through collaboration would help to explain our species' exceptional adaptiveness. It also aligns with evidence for substantial variability during our evolutionary history and the notion that humans are adapted not to a particular habitat but to variability itself. Specialization creates interdependence and necessitates balancing complementary strategies. Reframing DD therefore underscores the urgency of changing certain cultural practices to ensure we do not inhibit adaptation. Key improvements would remove cultural barriers to exploration and nurture explorative learning in education, academia, and the workplace, as well as emphasize collaboration over competition. Specialization in complementary search abilities represents a meta-adaptation; through collaboration, this likely enables human groups (as a species and as cultural systems) to successfully adapt. Cultural change to support this system of collaborative search may therefore be essential in confronting the challenges humanity now faces.

Relative Age Effect in Attention Deficit/Hyperactivity Disorder at Various Stages of the Medicalization Process

Diagnosis and pharmacological treatment of ADHD are more common among the youngest children in a classroom, born in the months immediately preceding the school entry cutoff date. The mechanisms behind this phenomenon, called the relative age effect (RAE), are not yet well understood. Nearly all hypotheses involve the school system, various teachers’ actions, and concern children’s immaturity. However, most previous studies have been based on reports of health professionals’ diagnoses and prescriptions found in official databases rather than on reports of teachers’ behavior identification or suspicion of ADHD, despite their being at the first stages of the medicalization process. Our study overcomes this limitation by using reports of parents’ and teachers’ behavior identification or suspicion of ADHD within a three-level multilevel survey design, comprising 1294 children, 130 teachers, and 17 elementary public schools. The goal of our study was to investigate whether RAE stems (1) from adults’ judgement of the child’s expression of immaturity or (2) from the consequences associated with the child’s double burden of being immature and exhibiting ADHD behaviors. Our multilevel analyses put forward the first hypothesis only, supporting the medicalization of immaturity. RAE in ADHD seems mostly initiated by teachers’ pre-diagnostic actions toward younger children.

Annual Research Review: Attention-deficit/hyperactivity disorder in girls and women: underrepresentation, longitudinal processes, and key directions

Attention-deficit/hyperactivity disorder (ADHD) - and its underlying behavioral dimensions of inattention and hyperactivity-impulsivity - have been understudied in females. We first cover the conceptual issues of prevalence, diagnostic practices, diversity, comorbidity, and causal factors, plus forces limiting awareness of ADHD in females. After a narrative review of cross-sectional and longitudinal findings, we conclude the following. (a) Girls meet diagnostic criteria for ADHD at just under half the rates of boys, a ratio that becomes much closer to equal by adulthood. (b) Girls and women with ADHD show a predominance of inattention and associated internalizing problems; boys and men display greater levels of hyperactive-impulsive symptoms and associated externalizing problems. (c) Sex differences in ADHD symptoms and related outcomes depend heavily on the clinical versus nonreferred nature of the samples under investigation. (d) Females with ADHD experience, on average, serious impairments, with a particularly heightened risk for problems in close relationships and engagement in self-harm. (e) Clinicians may overlook symptoms and impairments in females because of less overt (but still impairing) symptom manifestations in girls and women and their frequent adoption of compensatory strategies. Our review of predictors and mediators of adult outcomes highlights (a) the potential for heterotypically continuous pathways in females with childhood ADHD and (b) developmental progressions to self-harm, intimate partner violence, unplanned pregnancy, and comorbid psychopathology. Focusing on ADHD in females is necessary to characterize causal and maintaining mechanisms with accuracy and to foster responsive interventions, as highlighted in our closing list of clinical implications and research priorities.

Editorial: Youngest Kids in Class and Their Long-term Outcomes

In this issue of the JAACAP, Kuntsi et al.⁷ reports from the Swedish national registers to analyze the outcomes of almost 300,000 individuals who were relatively young or relatively old in class (ie, born in the 2 months before and after the national cut-off for school entrance in Sweden). Four events were measured between 15 and 23 years of age: low educational achievement, a conviction of any crime, substance use disorder, and depression. As predicted, young relative age was a risk factor for ADHD (with an odds ratio of 1.7), which in turn was a risk factor for all 4 outcomes considered (with odds ratios of 3.5-5.2). The novelty of their analyses, however, was to evaluate the additive effects of relative young age beyond ADHD on negative long-term outcomes. For the first time, Kuntsi et al.⁷ demonstrated that children with ADHD who are the youngest in their class are at increased risk for lower educational achievement and receiving a diagnosis of substance use disorder when compared to children with ADHD who are the oldest in their class.

Relative Age and the Use of Second-Generation Antipsychotics from 7 to 17 Years of Age: A Population-Based Register Study

Objective: The youngest children in a classroom have a higher risk of attention-deficit/hyperactivity disorders (ADHDs) and depression than their relatively older peers. However, there has been a lack of research on how relative age is related to second-generation antipsychotic (SGA) medication use. Methods: This study used the Finnish National Prescription Register data and comprised all 669,726 Finnish children and adolescents aged 7-17 in 2018. We extracted data for those who were dispensed SGAs (risperidone, quetiapine, aripiprazole, and olanzapine) and ADHD medication (methylphenidate, atomoxetine, dexamphetamine, and lisdexamfetamine). Odds ratios (OR) and 95% confidence intervals (CI) were calculated for medication dispensed to schoolchildren born from January to April (the relatively oldest), May to August, and September to December (the relatively youngest). Dispensed prescriptions were a proxy for medication use. Results: SGAs were dispensed to 9146 (1.4%) individuals in 2018. Their use was lower among girls aged 12-17 years born from September to December than January to April (OR 0.89; 95% CI 0.83-0.97), with no association between SGA use and birth month among boys. However, younger relative age was associated with combined SGA and ADHD medication, which was used by 2556 (0.4%) of the cohort: 2074 (0.6%) boys and 482 (0.1%) girls. The OR was 1.27 for boys aged 12-17 born from September to December (95% CI 1.10-1.46), compared with January to April. The OR for girls born from May to August was 1.35 (95% CI 1.04-1.76) and from September to December it was 1.33 (95% CI 1.02-1.74), compared with January to April. Conclusions: A novel discovery of this study was that using both SGA and ADHD medication at the age of 12-17 years was more common among the youngest subjects in a school year than their relatively older peers.

Meta-Analysis Study on Treatment of Children's Attention Deficit Disorder with Hyperactivity

With the development of society and the economy, the prevalence of attention deficit hyperactivity disorder (ADHD) has been increasing. Due to its high comorbidity and high harm, it has received increasing attention. It causes damage to functions in multiple areas, and this damage may continue into adulthood. ADHD is a common developmental disorder characterized by persistent attention deficit and hyperactivity/impulsivity. ADHD often merges with other diseases, such as oppositional defiant disorder, conduct disorder, personality disorder, anxiety disorder, mood disorder, and substance dependence. The disease tends to cause children with learning difficulties, poor grades, strained relationships with family members and children of the same age, lack of self-esteem, and children with low occupation, low income, substance abuse, and antisocial personality characteristics when they grow up to adults. Many countries have formulated ADHD treatment guidelines for this purpose, but there is still a lack of consensus. This article uses literature research and the meta method: RevMan 5.3 software is used for data analysis. The analysis results show that traditional Chinese medicine has characteristics and advantages in the clinical total effective rate and hyperactivity index score in the treatment of ADHD. The overall clinical syndrome differentiation of the treatment can be summarized as liver and kidney yin deficiency and liver yang partial prosperity. The overall medication is based on the methods of nourishing yin and clearing heat, calming the liver and nourishing kidney, and nourishing yin and suppressing yang. The efficacy and safety evaluation of traditional Chinese medicine in the treatment of ADHD need to be further verified by large-sample clinical trials with strict design and standardized outcome index reporting.

Trends of Mental Disorders and Treatment Continuity Predictors of New Patients in the Paediatric Psychiatry Clinic of a University Hospital

This study analysed trends of first-time patients visiting the paediatric psychiatry clinic in a university hospital. The medical records from 2009 to 2016 of first-time patients visiting the Kyung Hee University Hospital were reviewed, focusing on children in grades 1–12. We analysed the clinical diagnosis rate of mental disorders per 100,000 in the general population by gender and grade, and the characteristics of patients who sought outpatient care more than three times. The study included 1467 participants, of which 931 were males (63.5%). The number of male patients per 100,000 population significantly decreased from 4.14 in 2009 to 2.03 in 2016. While hyperkinetic disorders had the highest prevalence in males, neurotic disorders were most frequent in females. The rate of disruptive behaviour disorders in males and mental retardation in females decreased significantly during the data collecting period. The factors affecting treatment continuity were being female, 7th–12th graders, and diagnosis of depressive, hyperkinetic, and tic disorders. Physicians should consider the new paediatric patients’ gender, grade, and expected diagnosis from their first visit to improve treatment compliance.

The World Federation of ADHD International Consensus Statement: 208 Evidence-based conclusions about the disorder

BACKGROUND

Misconceptions about ADHD stigmatize affected people, reduce credibility of providers, and prevent/delay treatment. To challenge misconceptions, we curated findings with strong evidence base.

METHODS

We reviewed studies with more than 2000 participants or meta-analyses from five or more studies or 2000 or more participants. We excluded meta-analyses that did not assess publication bias, except for meta-analyses of prevalence. For network meta-analyses we required comparison adjusted funnel plots. We excluded treatment studies with waiting-list or treatment as usual controls. From this literature, we extracted evidence-based assertions about the disorder.

RESULTS

We generated 208 empirically supported statements about ADHD. The status of the included statements as empirically supported is approved by 80 authors from 27 countries and 6 continents. The contents of the manuscript are endorsed by 366 people who have read this document and agree with its contents.

CONCLUSIONS

Many findings in ADHD are supported by meta-analysis. These allow for firm statements about the nature, course, outcome causes, and treatments for disorders that are useful for reducing misconceptions and stigma.

Relative age and specific learning disorder diagnoses: A Finnish population-based cohort study

Background

Being among the youngest in class has previously been associated with attention-deficit/hyperactivity disorder (ADHD) and academic disadvantage, but the relative age effect on learning disorders is less well understood. This study examined whether relatively young children are more likely to be diagnosed with specific learning disorders than their older peers.

Methods

The setting included all 388,650 children born singleton in Finland from 1996 to 2002. Cases diagnosed with specific learning disorders in specialized health care by the age of 10 were identified from national registers. Cumulative incidences of specific learning disorders and the corresponding incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were calculated for each birth month compared to January.

Results

During follow-up, 3162 (0.8% of 388,650) children were diagnosed with a specific learning disorder. Children born in December displayed higher cumulative incidences for specific learning disorders than children born in January (IRR: 1.77, 95% CI: 1.50-2.11). The findings were similar for girls (IRR: 2.01, 1.44-2.83) and boys (IRR: 1.70, 1.39-2.08). ADHD did not explain the association, as the IRR for the youngest children with specific learning disorders and ADHD was 1.59 (1.13-2.26) compared to those without ADHD (IRR: 1.84, 1.51-2.24).

Conclusions

Relatively younger children in Finnish schools were more likely to be diagnosed with a specific learning disorder by the age of 10. Increased awareness of how relative age differences affect the likelihood for children to be diagnosed with specific learning disorders is needed among parents, clinicians, and teachers.

Predictors of ADHD persistence in elementary school children who were assessed in earlier grades: A prospective cohort study from Istanbul, Turkey

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorders among school-age children worldwide. In a more recent follow-up study, Biederman et al. found that 78% of children diagnosed with ADHD between the ages of 6-17 years continued to have a full (35%) or a partial persistence after eleven years.

OBJECTIVE

In this study, it was aimed to identify the factors contributing to the persistence of ADHD symptoms in elemantary school children who were prospectively assessed both in their earlier and upper grades.

METHODS

The sample was drawn from a previous community-based study where ADHD symptoms in 3696 first/or second graders were examined in regard to their school entry age. Two years after, the families of the children that participated in the initial study were called by phone and invited to a re-evaluation session. Among those who were reached, 154 were consequently eligible and were assessed with Swanson, Nolan and Pelham questionnaire (SNAP-IV), Conners' rating scales (CRS) and the Kiddie schedule for affective disorders and schizophrenia (K-SADS).

RESULTS

Of the 154 children, 81 had been evaluated to have "probable ADHD" by the initial interview. Among these 81 children, 50 (61.7%) were indeed diagnosed with ADHD after two years. Initial scores of the teacher reported SNAP-IV inattention subscale predicted the ADHD diagnosis after two years, with an odds ratio of 1.0761 (p = 0.032, Wald: 4.595).

CONCLUSIONS

Our results suggest that high inattention symptom scores reported by the teacher in the earlier grades, might predict an ADHD diagnosis in upper grades.

Environmental risk factors, protective factors, and peripheral biomarkers for ADHD: an umbrella review

BACKGROUND

Many potential environmental risk factors, environmental protective factors, and peripheral biomarkers for ADHD have been investigated, but the consistency and magnitude of their effects are unclear. We aimed to systematically appraise the published evidence of association between potential risk factors, protective factors, or peripheral biomarkers, and ADHD.

METHODS

In this umbrella review of meta-analyses, we searched PubMed including MEDLINE, Embase, and the Cochrane Database of Systematic Reviews, from database inception to Oct 31, 2019, and screened the references of relevant articles. We included systematic reviews that provided meta-analyses of observational studies that examined associations of potential environmental risk factors, environmental protective factors, or peripheral biomarkers with diagnosis of ADHD. We included meta-analyses that used categorical ADHD diagnosis criteria according to DSM, hyperkinetic disorder according to ICD, or criteria that were less rigorous than DSM or ICD, such as self-report. We excluded articles that did not examine environmental risk factors, environmental protective factors, or peripheral biomarkers of ADHD; articles that did not include a meta-analysis; and articles that did not present enough data for re-analysis. We excluded non-human studies, primary studies, genetic studies, and conference abstracts. We calculated summary effect estimates (odds ratio [OR], relative risk [RR], weighted mean difference [WMD], Cohen's d, and Hedges' g), 95% CI, heterogeneity I² statistic, 95% prediction interval, small study effects, and excess significance biases. We did analyses under credibility ceilings, and assessed the quality of the meta-analyses with AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews 2). This study is registered with PROSPERO, number CRD42019145032.

FINDINGS

We identified 1839 articles, of which 35 were eligible for inclusion. These 35 articles yielded 63 meta-analyses encompassing 40 environmental risk factors and environmental protective factors (median cases 16 850, median population 91 954) and 23 peripheral biomarkers (median cases 175, median controls 187). Evidence of association was convincing (class I) for maternal pre-pregnancy obesity (OR 1·63, 95% CI 1·49 to 1·77), childhood eczema (1·31, 1·20 to 1·44), hypertensive disorders during pregnancy (1·29, 1·22 to 1·36), pre-eclampsia (1·28, 1·21 to 1·35), and maternal acetaminophen exposure during pregnancy (RR 1·25, 95% CI 1·17 to 1·34). Evidence of association was highly suggestive (class II) for maternal smoking during pregnancy (OR 1·6, 95% CI 1·45 to 1·76), childhood asthma (1·51, 1·4 to 1·63), maternal pre-pregnancy overweight (1·28, 1·21 to 1·35), and serum vitamin D (WMD -6·93, 95% CI -9·34 to -4·51).

INTERPRETATION

Maternal pre-pregnancy obesity and overweight; pre-eclampsia, hypertension, acetaminophen exposure, and smoking during pregnancy; and childhood atopic diseases were strongly associated with ADHD. Previous familial studies suggest that maternal pre-pregnancy obesity, overweight, and smoking during pregnancy are confounded by familial or genetic factors, and further high-quality studies are therefore required to establish causality.

FUNDING

None.

Editorial: Relative Immaturity or Attention-Deficit/Hyperactivity Disorder: A Diagnostic Dilemma?

Attention-deficit/hyperactivity disorder (ADHD) is among the most common disorders of childhood¹ and causes significant morbidity throughout the life span.² Appropriate diagnosis and treatment of ADHD are thus critically important. The diagnosis of ADHD, however, is not straightforward. Clinicians must rely on parent and teacher reports of the child's behavior in comparison to other children the same age.³ Although various tests or procedures may be helpful in the diagnosis of ADHD, none of them obviates the need to rely on parent and teacher reports. Making matters more complicated, the agreement between parent and teacher reports of a child's ADHD-like behavior is low.⁴.

Association Between Greenness Surrounding Schools and Kindergartens and Attention-Deficit/Hyperactivity Disorder in Children in China

IMPORTANCE

Few studies have investigated the association between greenness and childhood attention-deficit/hyperactivity disorder (ADHD).

OBJECTIVE

To evaluate the association between greenness surrounding schools or kindergartens and symptoms of ADHD in children.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cross-sectional study was performed between April 2012 and January 2013 in 7 cities in northeastern China. This analysis included 59 754 children (aged 2-17 years) from 94 schools and kindergartens, who had resided in the study area for 2 years or longer. Data were analyzed from April 15, 2019, to October 10, 2019.

EXPOSURES

Greenness surrounding each child's school or kindergarten was estimated using 2 satellite image-derived vegetation indexes: the normalized difference vegetation index and the soil-adjusted vegetation index.

MAIN OUTCOMES AND MEASURES

Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) scales were used to measure ADHD symptoms (9 inattention symptoms and 9 hyperactivity-impulsivity symptoms). Parents or guardians rated the frequency of each of 18 ADHD symptoms during the preceding 6 months. Children with 6 or more symptoms of either inattention or hyperactivity-impulsivity were defined as having ADHD symptoms. Generalized linear mixed models were applied to estimate the association between greenness and ADHD symptoms.

RESULTS

The mean (SD) age of the 59 754 study participants was 10.3 (3.6) years, and 29 494 (49.4%) were girls. A total of 2566 participants (4.3%) had ADHD symptoms. Greenness levels differed substantially across schools and kindergartens. The normalized difference vegetation index within 500 m of a school or kindergarten ranged from -0.09 to 0.77. Greater greenness levels were associated with lower odds of ADHD symptoms. In covariate-adjusted models, a 0.1-unit increase in normalized difference vegetation index or soil-adjusted vegetation index within 500 m of a school or kindergarten was significantly associated with lower odds of ADHD symptoms (odds ratios, 0.87 [95% CI, 0.83-0.91] and 0.80 [95% CI, 0.74-0.86], respectively; P < .001 for both). The associations were robust in a series of sensitivity analyses.

CONCLUSIONS AND RELEVANCE

These findings suggest that there may be a beneficial association between school-based greenness and ADHD symptoms in Chinese children. Future longitudinal and mechanistic studies are needed to confirm the findings of this cross-sectional analysis and further explore potential mechanisms of this association.