Geographic variation in ADHD treatment and diagnosis among children and adolescents is well documented, yet the system-level factors driving such differences remain poorly understood. We examined nationwide patterns of ADHD medication use and diagnoses in Denmark in 2024 and assessed whether municipal socioeconomy, regional hospital waiting times or private child psychiatrist capacity contributed to geographic variation. In this register-based cross-sectional study, we included all Danish residents aged 4-17 years using data from national registers. Pharmacological treatment was defined as at least one redeemed prescription for ADHD drugs, and diagnosis was defined as at least one hospital contact with ICD-10 codes F90.x/F98.8. Prevalence was calculated overall and stratified by sex and age, with associations explored using Spearman's rank correlations and regression analyses. ADHD medication prevalence varied sixfold across municipalities (9.6-58 per 1000), with parallel variation in diagnoses (15-74 per 1000) and the largest differences observed among adolescents. Municipal socioeconomic status was weakly and inversely correlated with medication use (ρ = -0.20, p = 0.049), but not diagnoses. Neither waiting times nor specialist capacity was significantly associated with either outcome. Marked geographic variation in ADHD medication use and diagnoses persists in Denmark despite a uniform healthcare framework, and appears largely unexplained by the system-level factors examined.

Atopic dermatitis (AD) and attention-deficit/hyperactivity disorder (ADHD) frequently co-occur in children and adolescents, increasing the disease burden and clinical complexity. Accumulating evidence suggests that children with AD have a higher risk of incident ADHD, a risk that is particularly pronounced in those with early-onset, severe AD, or significant sleep disturbances. The underlying mechanisms are hypothesized to involve the dysregulation of the "inflammation-itching-neurobehavioral" axis. This narrative review synthesizes current evidence regarding the epidemiology, potential mechanisms, and clinical management of this comorbidity. We propose that proactive screening and aggressive control of skin inflammation and pruritus are key to disrupting this vicious cycle.

Attention-deficit/hyperactivity disorder (ADHD) is the second most prevalent chronic pediatric condition worldwide. Its core ADHD symptoms-inattention, hyperactivity, and impulsivity-impair oral hygiene behaviors, and first-line medications such as methylphenidate may further increase oral disease risk. However, systematic epidemiological data on oral health status of children with ADHD remain limited in China. This study aimed to investigate oral health status of children with ADHD and identify factors associated with adverse oral health outcomes in this population.

Voiding dysfunction (VD) is a common condition in childhood that is associated with lower urinary tract symptoms and bowel dysfunction. It may also adversely affect patients' emotional, behavioral, and social functioning. This cross-sectional case-control study evaluated emotional and behavioral problems, attention-related symptoms, and cognitive disengagement syndrome (CDS) in children with VD and examined their relationship with lower urinary symptoms severity and constipation. VD was diagnosed according to International Children's Continence Society criteria using voiding diaries, imaging findings, and Dysfunctional Voiding Symptom Score (DVSS ≥ 9). Emotional and behavioral symptoms were assessed using the Strengths and Difficulties Questionnaire, and attention-related and CDS symptoms were evaluated with the Barkley Child Attention Scale (BCAS). The study population included 72 children aged 6-12 years with VD and 46 age- and sex-matched healthy controls. Children with VD showed significantly more severe attention-deficit/hyperactivity disorder (ADHD) symptoms, emotional problems, behavioral difficulties, and peer problems, as well as higher total difficulty scores compared with controls. Increasing DVSS were positively associated with greater emotional-behavioral difficulties and poorer quality of life. Children with both daytime and nighttime urinary incontinence and those with concomitant constipation exhibited the highest psychosocial burden. In contrast, CDS-related symptoms did not differ significantly between children with VD and healthy controls. Conclusion: These findings indicate that VD is associated with a substantial emotional and behavioral burden, particularly attention-related difficulties, whereas CDS does not appear to be specifically linked to VD. Routine psychological screening and a multidisciplinary, biopsychosocial approach may improve symptom management and quality of life in affected children.

Off-time pubertal development defined as pubertal onset or progression deviating meaningfully from age- and sex-matched normative expectations confers heightened risk for internalizing and externalizing psychopathology during adolescence. Children and adolescents with neurodevelopmental disorders (NDDs), including autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), carry pre-existing impairments in theory of mind (ToM) the capacity to represent and respond to the mental states of others that substantially compromise their capacity to navigate the increasingly complex social demands that puberty introduces. Evidence indicates that ASD is associated with elevated rates of precocious puberty and altered pubertal tempo, and that ADHD in females is linked to earlier pubertal onset with consequent internalizing symptom exacerbation; yet the mechanisms connecting pubertal timing, ToM impairment, and psychopathological risk in these populations have not been systematically reviewed. This scoping review, guided by the PRISMA extension for Scoping Reviews (PRISMA-ScR), synthesises evidence from 19 studies (2016-2026) examining pubertal timing in ASD and ADHD, the neurobiological mechanisms linking puberty to social cognition, and the clinical and psychopathological consequences of their convergence. We identify three mechanisms through which off-time puberty and pre-existing ToM impairment interact: (1) demand-capacity mismatch amplification, (2) masking and camouflaging under elevated social load, and (3) physical-cognitive developmental asynchrony. No primary studies have directly examined the moderating role of ToM on the puberty-psychopathology relationship in NDD populations, representing a critical research gap. We propose a dual-vulnerability framework and outline research priorities for future longitudinal and intervention studies in this underserved population.

The co-existence of autism and attention deficit/hyperactivity disorder in tic disorders is a key factor influencing clinical decision-making. Given the shared clinical features and a potentially overlapping aetiology, the need to identify specific tic characteristics associated with these conditions remains. The current study subsequently sought to identify tic phenomenology uniquely predicted by autism and attention deficit/hyperactivity disorder traits in children and adolescents. Data from 473 5-16-year-olds from the 2004 British Child and Adolescent Mental Health Survey with motor and/or vocal tics were used. Regression analyses were conducted to determine the effect of autism and attention deficit/hyperactivity disorder traits on: (i) the presence of motor and/or vocal tics, (ii) tic onset age, (iii) nocturnal tic expression, (iv) self-regulatory control over tic expression, (v) tic frequency during restful/low arousal state, and (vi) rebound tic activity post-suppression, before and after adjustment for confounders. Autism is associated with earlier onset of tics by approximately 2.43 years. Attention deficit/hyperactivity disorder traits are associated with a 2.64x odds of experiencing worsening tics following periods of suppression. Neither autism or attention deficit/hyperactivity disorder traits were specifically associated with motor and/or vocal tics, self-regulatory control over tic expression, nocturnal tic expression, or tic frequency during restful/low arousal states. Comorbid neurodevelopmental traits not only co-occur with tic disorders but actively shape their clinical expression and trajectory. Clinically, earlier support for autistic children with tics may facilitate a timely intervention. Intervention plans for individuals with attention deficit/hyperactivity disorder traits should consider heightened vulnerability to tic rebound post-suppression.

Neurodevelopmental and neurodegenerative disorders are related disorders lying on a spectrum of neural dysfunction with overlapping molecular and cellular mechanisms. Early-life diseases like autism spectrum disorder and attention-deficit/hyperactivity disorder are the result of disturbed neurodevelopment, while late-onset diseases such as Alzheimer's disease and Parkinson's disease are defined by progressive neuronal loss and loss of function. Emerging evidence shows that environmental exposures are important, modifiable factors that affect brain health throughout the lifespan. Factors such as air pollution, heavy metals, pesticides, and endocrine-disrupting chemicals act in combination with genetic susceptibility to disrupt neurogenesis, synaptic plasticity, and neuro-immune signaling. These exposures cause persistent epigenetic modifications, oxidative stress, mitochondrial dysfunction, and chronic neuro-inflammation, linking early developmental insults to neurodegenerative processes later in life. The concepts of the exposome and the developmental origins of health and disease provide additional support for the cumulative, lifelong impact of environmental interactions. Mechanistically, the recurrent process of neuronal damage is caused by impaired proteostasis, microglial stimulation, and blood-brain barrier dysfunction. Furthermore, the gut-brain axis is a hyperactive system in which immune responses and microbial metabolites trigger neurobiological responses to external stimuli. This review integrates multidisciplinary evidence to elucidate the mechanism and emphasizes environmental risk mitigation and translational strategies to reduce disease burden and promote lifelong brain resilience.

Cognitive impairment is a major source of disability in neurodegenerative conditions, and it is also highly prevalent in autism spectrum disorder and attention-deficit/hyperactivity disorder. Across these conditions, subclinical epileptiform activity and resting-state functional hyperactivity have been repeatedly described, suggesting a shared state of cortical hyperexcitability. The LENDÜLET Neurocognitive Research Project aims to determine the incidence and multimodal characteristics of cortical hyperexcitability in multiple patient populations and to elucidate how hyperexcitability relates to cognitive performance, large-scale network connectivity, sleep-dependent memory consolidation, and tau/amyloid burden.

Speech segmentation is fundamental to language acquisition and supported by statistical learning (SL). Research on SL is inconclusive as to whether it can occur outside the scope of attention and whether SL is impaired in individuals with Attention-Deficit/Hyperactivity Disorder (ADHD). Furthermore, individual differences in SL are hypothesized to be influenced by other cognitive abilities such as musical rhythmic ability (RA) and phonological working memory (WM), which previous literature indicated may be impaired in ADHD. The current study investigated SL in participants diagnosed with ADHD (N = 41) and neurotypical (N = 118) peers, exposing them to an artificial language and assessing SL both during exposure using EEG-measures of neural entrainment, as well as behaviorally after exposure. Furthermore, we explored whether multiple tasks assessing RA and WM were related to SL ability, and how SL related to vocabulary size. Bayesian statistical evidence indicated absence of group differences on SL, RA, WM, and vocabulary. Instead, individual variability outweighed group effects. Combining the groups yielded anecdotal evidence for a positive correlation between SL and vocabulary size, but not between SL and RA or WM. These results suggest that SL operates comparably in our samples of neurotypical individuals and individuals with ADHD, and was not found to be related to tasks assessing RA or WM. Notably, our sample consisted of mostly female participants in both groups. Future studies may want to further examine gender differences in ADHD symptoms and take a dimensional approach to ADHD symptomatology in relation to individual differences in SL ability.

Stimulant medication is the first-line pharmacological treatment option for children with attention-deficit/hyperactivity disorder (ADHD). However, long-term effects remain unclear. Therefore, we explored long-term (>12 years) outcomes of childhood stimulant medication use, using data from the Dutch NeuroIMAGE cohort. Childhood (up to Mage=16.14, SDage=3.48) stimulant treatment trajectories were detected using K-means clustering based on age at initiation, stop age, total and maximum daily dose, and duration and variability of stimulant use in 324 children. The trajectories were compared across seven domains of adult outcomes (controlling for multiple testing) including psychiatric status, behavioral and emotional functioning, academic and professional functioning, adaptive functioning, neurocognitive functioning, physical health, and healthcare service use. At follow-up, 143 adults with childhood ADHD (Mage=28.34, SDage=3.74, 65% males) were part of three stimulant treatment trajectory groups: early-and-intense (n = 46), late-and-moderate (n = 63), and stimulant-naïve (n = 34). The three groups did not differ on any of the 51 adult outcomes and findings did not change after controlling for age and sex, except that a significant group difference emerged for callous and unemotional traits (behavioral and emotional functioning domain). More specifically, the early-and-intense and late-and-moderate groups had more favorable scores compared to stimulant-naïve group, although this may partly reflect pre-existing group differences. The main findings did not change after controlling for ADHD medication use at wave IV. Overall, stimulant medication use in childhood did not predict long-term outcomes in those with childhood ADHD in our sample, suggesting that there may be no lasting effects of stimulants on many long-term functional outcomes.

Thyroid hormones regulate embryonic and fetal neurodevelopment, with the maternal thyroid gland exclusively producing these hormones for the first half of gestation and then a combination of maternal and fetal production occurring during the second half of gestation. Hypothyroidism during pregnancy is common in humans, particularly due to the additional demand put on the thyroid gland as pregnancy proceeds. Epidemiological studies have linked maternal hypothyroidism to an increased risk of attention-deficit/hyperactivity disorder and autism spectrum disorder diagnosis in these children, as well as cognitive deficits and delays. Rodent models have been extensively used to model developmental hypothyroidism and study the long-term effects on offspring. Increases in activity, reductions in anxiety, cognitive impairments, and social alterations have been observed. In this review, I discuss the current understanding of the organizational impacts of hypothyroidism on activity, affective behaviors, cognition, and social behaviors in humans and animal models, paying special attention to critical periods that may underlie these effects. I also review potential interactions between thyroid hormones and steroid hormones known to be important for organization of the brain and behavior during perinatal and adolescent development. Understanding the effects of developmental hypothyroidism is critical, as early developmental exposure to many endocrine-disrupting chemicals may alter behavior through reducing thyroid hormone signaling, and the final section of the paper reviews these interactions. Understanding the organizational effects of thyroid hormones is important for decisions related to screening and interventions during pregnancy.