ADHD, altered dopamine neurotransmission, and disrupted reinforcement processes: implications for smoking and nicotine dependence

Transcriptomic Dysregulation in Animal Models of Attention-Deficit Hyperactivity Disorder and Nicotine Dependence Suggests Shared Neural Mechanisms

INTRODUCTION

Attention-deficit-hyperactivity disorder (ADHD) is highly heritable and increases the likelihood of nicotine dependence (ND). The self-medication hypothesis of nicotine use in ADHD proposes that ADHD patients seek nicotine for its ability to improve their symptoms, and they have less success quitting, possibly due to the worsening of ADHD symptoms in withdrawal.

METHODS

The present analysis compared transcriptomic data from the brains of rodent models of ADHD and those of ND, with a focus on striatal gene expression. Differential expression analysis, pathway enrichment analysis, and gene-network mapping identified signaling networks and candidate genes that may contribute to the high co-occurrence between ADHD and ND.

RESULTS

We identified novel differentially expressed genes (PRKAG2, MAPK1), and genes with known associations to either ADHD or ND (ANK3, CALD1, CHRNA4, CHRNA7, CMTM8, DLG4, DUSP6, GNG3, GNG11, GRIK5, GRINA2, GRM5, ICAM2, KCNJ6, PRKAB1, SNAP25, SYNPO, SYT1, VAMP2). In addition, synaptic transmission (hsa04728, R-HAS-112315, R-HSA-442755) and MAPK signaling pathways (hsa04010, hsa04014, hsa04015, R-HSA-5673001, R-HSA-5684996) were enriched in both ADHD and ND.

CONCLUSION

The signaling pathways implicated by this analysis mediate neurological mechanisms known to contribute to ND. The association of analogous differently expressed genes and common signaling pathways suggests an important causal relationship between ND and ADHD that may be clinically important.

Interpretable machine learning approaches for children's ADHD detection using clinical assessment data: an online web application deployment

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is a prevalent mental disorder characterized by hyperactivity, impulsivity, and inattention. This study aims to develop a verifiable and interpretable machine learning model to identify ADHD and its subtypes in children using clinical assessment scales data.

METHODS

This study utilized the ADHD-200 dataset, including demographic data, Behavioral Rating Scale, and Wechsler Intelligence Scale assessments, to train and validate our models. The model's performance was evaluated using 10-fold cross-validation within the internal dataset, and the best model will be used for external validation. Seven machine learning models were evaluated. The SHapley Additive exPlanations (SHAP) method was employed for model interpretation. Finally, a web application will deploy the prediction model to provide ADHD probabilities based on user input.

RESULTS

The Random Forest (RF) model performing best in identifying ADHD and the Support Vector Machine (SVM) model excelling in distinguishing ADHD subtypes. The RF model achieved an AUC of 0.99 in 10-fold cross-validation and an AUC of 0.99 in external validation, and the SVM model achieved a micro-average AUC of 0.96 and an accuracy of 0.83 in internal validation and a micro-average AUC of 0.96 and an accuracy of 0.85 in external validation. We used SHAP to interpret the models, revealing that higher ADHD Index pushed the model towards ADHD classification. Additionally, lower IQ scores were correlated with a higher likelihood of ADHD, consistent with previous studies. The dependency analysis found that the model can identify different behavioral scales. We deployed the final model online using a web application and showed users how the model made decisions.

CONCLUSIONS

Our findings highlight the potential of using machine learning and clinical assessment scales to support the diagnosis and subtype identification of ADHD in children, offering a practical solution for improving diagnostic accuracy and efficiency in clinical settings.

Factors associated with attention-deficit/hyperactivity disorder among Tunisian children

Introduction

Attention-deficit/hyperactivity disorder (ADHD) is a chronic neurodevelopmental condition that affects millions of children and adolescents worldwide. Knowledge of risk factors associated with ADHD may reduce its prevalence and its severe impact on patient's quality of life. The aim of this study was to identify risk factors associated with ADHD and to discuss their involvement in the genesis of the disorder.

Methods

This is a case-control study involving a first group of 74 children (mean age = 9 years) diagnosed with ADHD. The second group included 80 healthy control children. They were randomly selected and matched for age and gender. A literature-based questionnaire assessing the socio-demographic data, biological and environmental factors associated with ADHD was administered to the parents. The diagnosis of ADHD group was made by a trained child psychiatrist according to the DSM-5 criteria supplemented by the Conners scales of parents and teachers. For the control group, we added to the questionnaire the MINI-kid section of ADHD to screen for possible presence of ADHD symptoms. Univariate then multivariate analyses were conducted to identify factors associated with ADHD.

Results

Several factors were more prevalent in children with ADHD than in controls: disturbed family dynamics, low socio-economic status, family history of psychiatric and organic pathologies, and particularly several early environmental factors, including passive smoking during pregnancy, prematurity, fetal distress, caesarean delivery and low birth weight. In the early childhood period, early exposure to television was also strongly associated with ADHD. However, the multivariate model conducted to determine the variables independently associated with ADD/ADHD revealed only three determining factors: passive smoking during pregnancy (OR = 4.60 [2.14, 9.94]; p < 0.001), acute fetal distress (OR = 5.08 [1.47, 17.52]; p = 0.01), and familial psychiatric history (OR = 9.37 [2.46, 35.59]; p = 0.001).

Discussion

The recognition of factors involved in the genesis of ADHD within different ethnic populations may help understanding and broaden our knowledge of this disorder to develop targeted strategies for prevention and early intervention. Further participants with more robust statistical output are required to confirm our findings to a more generalized population.

Dopaminergic Perturbation in the Aetiology of Neurodevelopmental Disorders

Brain development may be influenced by both genetic and environmental factors, with potential consequences that may last through the lifespan. Alterations during neurogenesis are linked to neurodevelopmental cognitive disorders. Many neurotransmitters and their systems play a vital role in brain development, as most are present prior to synaptogenesis, and they are involved in the aetiology of many neurodevelopmental disorders. For instance, dopamine (DA) receptor expression begins at the early stages of development and matures at adolescence. The long maturation period suggests how important it is for the stabilisation and integration of neural circuits. DA and dopaminergic (DAergic) system perturbations have been implicated in the pathogenesis of several neurological and neuropsychiatric disorders. The DAergic system controls key cognitive and behavioural skills including emotional and motivated behaviour through DA as a neurotransmitter and through the DA neuron projections to major parts of the brain. In this review, we summarise the current understanding of the DAergic system's influence on neurodevelopment and its involvement in the aetiology and progression of major disorders of the developing brain including autism, schizophrenia, attention deficit hyperactivity disorder, down syndrome, and fragile X syndrome.

Alterations in Striatal Architecture and Biochemical Markers' Levels During Postnatal Development in the Rat Model of an Attention Deficit/Hyperactivity Disorder (ADHD)

Attention deficit/hyperactivity disorder (ADHD) is defined as a neurodevelopmental condition. The precise underlying mechanisms remain incompletely elucidated. A body of research suggests disruptions in both the cellular architecture and neuronal function within the brain regions of individuals with ADHD, coupled with disturbances in the biochemical parameters. This study seeks to evaluate the morphological characteristics with a volume measurement of the striatal regions and a neuron density assessment within the studied areas across different developmental stages in Spontaneously Hypertensive Rats (SHRs) and Wistar Kyoto Rats (WKYs). Furthermore, the investigation aims to scrutinize the levels and activities of specific markers related to immune function, oxidative stress, and metabolism within the striatum of juvenile and maturing SHRs compared to WKYs. The findings reveal that the most pronounced reductions in striatal volume occur during the juvenile stage in SHRs, alongside alterations in neuronal density within these brain regions compared to WKYs. Additionally, SHRs exhibit heightened levels and activities of various markers, including RAC-alpha serine/threonine-protein kinase (AKT-1), glucocorticoid receptor (GCsRβ), malondialdehyde (MDA), sulfhydryl groups (-SH), glucose (G), iron (Fe), lactate dehydrogenase (LDH). alanine transaminase (ALT), and aspartate transaminase (AST). In summary, notable changes in striatal morphology and elevated levels of inflammatory, oxidative, and metabolic markers within the striatum may be linked to the disrupted brain development and maturation observed in ADHD.

Attention-deficit hyperactivity disorder is associated with risky and unhealthy behaviours among adolescents

OBJECTIVES

Attention-deficit hyperactivity disorder (ADHD) is highly prevalent among adolescents globally, particularly in Israel. This study aimed to evaluate associations between ADHD and engagement in risky/unhealthy behaviours among adolescents.

STUDY DESIGN

Cross-sectional study.

METHODS

Students participating in the 2015-2016 National Health Survey completed self-administered questionnaires, providing demographic, medical and behavioural information (n = 4616, 11-18 years old, 50.2% male). Multivariable logistic regression analyses assessed the associations between ADHD and risky/unhealthy behaviours, including current tobacco/hookah smoking, alcohol consumption (≥1 serving/month), excessive screen time (≥4 h/d), non-compliance with physical activity and sleep recommendations (<1 h/d, and <8 or <9 h/d depending on age, respectively) and unhealthy lifestyle (engagement in ≥3 of these behaviours).

RESULTS

A total of 752 participants reported ever being diagnosed with ADHD (287 of whom were treated with stimulants) and 3864 individuals were included in a non-ADHD comparison group. ADHD was significantly associated with higher prevalence of smoking (odds ratio [OR] 2.15; 95% confidence interval [CI]: 1.65, 2.80), alcohol consumption (OR 1.38; 95% CI: 1.10, 1.73) and excessive screen time [OR 1.41; 95% CI: 1.18, 1.70), each adjusted for sociodemographic characteristics and the other risky/unhealthy behaviours. Unhealthy lifestyle was twice as common in the ADHD group (OR 2.03; 95% CI: 1.64, 2.51). Stimulant-treated and non-treated adolescents with ADHD did not differ in demographic or behavioural characteristics.

CONCLUSIONS

ADHD was significantly associated with an unhealthy lifestyle among adolescents. These behaviours should be detected early and prevention measures put in place to limit their harmful consequences in this adolescent population. Additional large-scale prospective research is needed to deepen the understanding of this association.

Beyond the Brain: Attention Deficit/Hyperactivity Disorder and the Gut-Brain Axis

Attention-deficit/hyperactivity disorder (ADHD) is a complex neurodevelopmental condition, predominantly affecting children, characterized by inattention, hyperactivity, and impulsivity. A growing body of evidence has highlighted the potential influence of the gut microbiota on the onset and presentation of ADHD symptoms. The gut microbiota, a diverse microbial ecosystem residing within the gastrointestinal tract, exerts multiple effects on systemic physiology, including immune modulation, metabolic regulation, and neuronal signalling. The bidirectional gut-brain axis serves as a conduit for communication between gut microbes and the central nervous system, implicating its disruption in neurodevelopmental disorders such as ADHD. This comprehensive literature review aims to shed light on how alterations in the gut microbiota influence the development and manifestation of ADHD symptoms. Examining potential mechanisms involving gut microbial metabolites and their impact on neurotransmitter modulation, neuro-endocrine signalling and neuroinflammation, we dissect the intricate interplay shaping ADHD pathology. Insights into these complex interactions hold promise for personalized therapeutic interventions aimed at modulating the gut microbiota to ameliorate ADHD symptoms. Discussions encompass dietary interventions, faecal microbiota-targeted therapies, and emerging probiotic approaches, underscoring their potential as adjunctive or alternative strategies in managing ADHD. Further research elucidating the precise mechanisms driving these interactions may pave the way for targeted and personalized interventions for individuals grappling with ADHD.

A nitrogen-doped carbon nanosheet/poly(amidoamine) dendrimer-based electrochemical sensor for nicotine in flavored hookah pipe tobacco

Towards the nicotine addiction challenge in the smoking of hookah pipe products, we hereby present the development of an electrochemical sensor for nicotine detection. A nitrogen-doped carbon nanosheet (N-CNS)/poly(amidoamine) dendrimer (PAMAM) nanocomposite-modified electrode was prepared as a sensor for the detection of nicotine in analytical and real samples. The N-CNSs were prepared by a hydrothermal method and dropcast on a glassy carbon electrode followed by electro-deposition of the PAMAM dendrimer to form the sensor (GCE/N-CNSs/PAMAM). The N-CNSs were characterized with electron microscopy, Raman spectroscopy and FTIR. The sensor was characterized with voltammetry and electrochemical impedance spectroscopy. The N-CNS/PAMAM enhanced the electrochemical performance of the electrode towards the oxidation of nicotine. The sensor achieved a detection limit of 0.05 μM in a linear concentration range of 1.93-61.64 μM nicotine standard samples. The sensor showed good reproducibility, repeatability, and selectivity. The sensor was successful in selectively detecting nicotine in two local brands of hookah pipe tobacco with a 113-121 percent recovery. Nicotine, up to a concentration of 0.35-0.39 mg g-1, was found in the sampled hookah pipe tobacco products suggesting possible harm to human health.

Zuranolone therapy protects frontal cortex neurodevelopment and improves behavioral outcomes after preterm birth

BACKGROUND

Preterm birth is associated with brain injury and long-term behavioral abnormalities, for which there are limited prevention options. When born preterm, infants prematurely lose placental neurosteroid (allopregnanolone) support. This increases the risk of excitotoxic damage to the brain, which increases the risk of injury, causing long-term deficits in behavior, myelination, and alterations to neurotransmitter pathways. We propose that postnatal restoration of neurosteroid action through zuranolone therapy will reduce neurological impairments following preterm birth.

METHODS

Guinea pig dams underwent survival cesarean section surgery to deliver pups prematurely (GA64) or at term (GA69). Between birth and term equivalence age, preterm pups received vehicle (15% β-cyclodextrin) or the allopregnanolone analogue zuranolone (1 mg/kg/day). Behavioral analysis was performed at postnatal day (PND) 7 and 40, before tissue collection at PND 42. Immunostaining for myelin basic protein (MBP), as well as real-time polymerase chain reaction to characterize oligodendrocyte lineage and neurotransmitter pathways, was performed in frontal cortex tissues.

RESULTS

Zuranolone treatment prevented the hyperactive phenotype in preterm-born offspring, most markedly in males. Additionally, preterm-related reductions in MBP were ameliorated. Several preterm-related alterations in mRNA expression of dopaminergic, glutamatergic, and GABAergic pathways were also restored back to that of a term control level.

CONCLUSION

This is the first study to assess zuranolone treatment as a neuroprotective therapy following preterm birth. Zuranolone treatment improved behavioral outcomes and structural changes in the preterm offspring, which continued long term until at least a late childhood timepoint. Clinical studies are warranted for further exploring the neuroprotective possibilities of this treatment following preterm birth.

A Systematic Review and Meta-analysis of Chemical Exposures and Attention-Deficit/Hyperactivity Disorder in Children

Exposure to certain chemicals prenatally and in childhood can impact development and may increase risk for attention-deficit/hyperactivity disorder (ADHD). Leveraging a larger set of literature searches conducted to synthesize results from longitudinal studies of potentially modifiable risk factors for childhood ADHD, we present meta-analytic results from 66 studies that examined the associations between early chemical exposures and later ADHD diagnosis or symptoms. Studies were eligible for inclusion if the chemical exposure occurred at least 6 months prior to measurement of ADHD diagnosis or symptomatology. Included papers were published between 1975 and 2019 on exposure to anesthetics (n = 5), cadmium (n = 3), hexachlorobenzene (n = 4), lead (n = 22), mercury (n = 12), organophosphates (n = 7), and polychlorinated biphenyls (n = 13). Analyses are presented for each chemical exposure by type of ADHD outcome reported (categorical vs. continuous), type of ADHD measurement (overall measures of ADHD, ADHD symptoms only, ADHD diagnosis only, inattention only, hyperactivity/impulsivity only), and timing of exposure (prenatal vs. childhood vs. cumulative), whenever at least 3 relevant effect sizes were available. Childhood lead exposure was positively associated with ADHD diagnosis and symptoms in all analyses except for the prenatal analyses (odds ratios (ORs) ranging from 1.60 to 2.62, correlation coefficients (CCs) ranging from 0.14 to 0.16). Other statistically significant associations were limited to organophosphates (CC = 0.11, 95% confidence interval (CI): 0.03-0.19 for continuous measures of ADHD outcomes overall), polychlorinated biphenyls (CC = 0.08, 95% CI: 0.02-0.14 for continuous measures of inattention as the outcome), and both prenatal and childhood mercury exposure (CC = 0.02, 95% CI: 0.00-0.04 for continuous measures of ADHD outcomes overall for either exposure window). Our findings provide further support for negative impacts of prenatal and/or childhood exposure to certain chemicals and raise the possibility that primary prevention and targeted screening could prevent or mitigate ADHD symptomatology. Furthermore, these findings support the need for regular review of regulations as our scientific understanding of the risks posed by these chemicals evolves.

Dysfunctional hippocampal-prefrontal network underlies a multidimensional neuropsychiatric phenotype following early-life seizure

Brain disturbances during development can have a lasting impact on neural function and behavior. Seizures during this critical period are linked to significant long-term consequences such as neurodevelopmental disorders, cognitive impairments, and psychiatric symptoms, resulting in a complex spectrum of multimorbidity. The hippocampus-prefrontal cortex (HPC-PFC) circuit emerges as a potential common link between such disorders. However, the mechanisms underlying these outcomes and how they relate to specific behavioral alterations are unclear. We hypothesized that specific dysfunctions of hippocampal-cortical communication due to early-life seizure would be associated with distinct behavioral alterations observed in adulthood. Here, we performed a multilevel study to investigate behavioral, electrophysiological, histopathological, and neurochemical long-term consequences of early-life Status epilepticus in male rats. We show that adult animals submitted to early-life seizure (ELS) present working memory impairments and sensorimotor disturbances, such as hyperlocomotion, poor sensorimotor gating, and sensitivity to psychostimulants despite not exhibiting neuronal loss. Surprisingly, cognitive deficits were linked to an aberrant increase in the HPC-PFC long-term potentiation (LTP) in a U-shaped manner, while sensorimotor alterations were associated with heightened neuroinflammation, as verified by glial fibrillary acidic protein (GFAP) expression, and altered dopamine neurotransmission. Furthermore, ELS rats displayed impaired HPC-PFC theta-gamma coordination and an abnormal brain state during active behavior resembling rapid eye movement (REM) sleep oscillatory dynamics. Our results point to impaired HPC-PFC functional connectivity as a possible pathophysiological mechanism by which ELS can cause cognitive deficits and psychiatric-like manifestations even without neuronal loss, bearing translational implications for understanding the spectrum of multidimensional developmental disorders linked to early-life seizures.

Exploring Differences in Physical Health in Young Children With and Without ADHD

OBJECTIVE

To assess differences in child physical health outcomes and metrices associated with obesity in a sample of predominantly Hispanic/Latinx young children with and without attention-deficit/hyperactivity disorder (ADHD).

METHODS

Participants included 127 children diagnosed with ADHD and 96 typically developing (TD) children between 4 and 7 years of age. Objective measures of children's body composition, fitness, and physical activity were conducted. Parents of children completed food recalls to assess their child's dietary intake, diet quality was calculated based on the Healthy Eating Index-2015, and parents completed a survey about their family's health habits.

RESULTS

Logistic regression revealed that those with ADHD were more likely to be classified as having an overweight or obese (Ov/O) body mass index (BMI). Linear regression analyses indicated that children with ADHD performed worse on a fitness test and consumed more calories relative to TD children. Moderation analyses indicated that sex differences in steps were prominent in our TD sample, but not among those with ADHD.

CONCLUSIONS

Young children with ADHD are at greater risk for having an Ov/O BMI, being less fit, and eating a greater intake of calories compared to TD children.

A new mechanistic insight into the association between environmental perfluorooctane sulfonic acid (PFOS) exposure and attention deficit and hyperactivity disorder (ADHD)-like behavior

Perfluorooctane sulfonic acid (PFOS) is one of the main residual environmental pollutants that threaten human health. PFOS exposure is positively correlated with the prevalence of attention deficit hyperactivity disorder (ADHD); however, the underlying mechanism is unknown. Given that dopamine (DA) is a crucial target for PFOS and that its dysfunction is a key role in ADHD development, it is speculated that PFOS exposure contributes to the occurrence of ADHD to some extent by disrupting DA homeostasis. To establish the relationship between PFOS exposure, DA dysfunction, and ADHD-like behavior, adult zebrafish were exposed to PFOS for 21 days using PFOS concentrations in the serum of patients with ADHD as the reference exposure dose. Results showed that PFOS caused ADHD-like behaviors, with the presence of the slightly elevated percentage of time spent in movement and prolonged time spent in reaching the target zone in the T-maze. Hyperactivity and cognitive ability impairment were more severe with increasing PFOS concentrations. Further investigation showed that PFOS exposure resulted in a decrease in the DA content, accompanied by a decrease in the number of dopaminergic neurons and a disturbance in the transcription profiles of genes associated with the dopaminergic system. Treatment with Ritalin effectively alleviated PFOS-induced ADHD-like behavior and restored DA levels, number of dopaminergic neurons, and expression of DA metabolism-related genes, suggesting that PFOS exposure induced ADHD-like behavior by triggering DA secretion disorder. This study enriches our understanding of the pathogenic mechanisms underlying ADHD development and emphasizes the importance of focusing on the health risks pertaining to environmental exposure.

Methylphenidate as a treatment option for substance use disorder: a transdiagnostic perspective

A transition in viewing mental disorders from conditions defined as a set of unique characteristics to one of the quantitative variations on a collection of dimensions allows overlap between disorders. The overlap can be utilized to extend to treatment approaches. Here, we consider the overlap between attention-deficit/hyperactivity disorder and substance use disorder to probe the suitability to use methylphenidate as a treatment for substance use disorder. Both disorders are characterized by maladaptive goal-directed behavior, impaired cognitive control, hyperactive phasic dopaminergic neurotransmission in the striatum, prefrontal hypoactivation, and reduced frontal cortex gray matter volume/density. In addition, methylphenidate has been shown to improve cognitive control and normalize associated brain activation in substance use disorder patients and clinical trials have found methylphenidate to improve clinical outcomes. Despite the theoretical basis and promising, but preliminary, outcomes, many questions remain unanswered. Most prominent is whether all patients who are addicted to different substances may equally profit from methylphenidate treatment.

Adolescent ADHD and electrophysiological reward responsiveness: A machine learning approach to evaluate classification accuracy and prognosis

We evaluated event-related potential (ERP) indices of reinforcement sensitivity as ADHD biomarkers by examining, in N=306 adolescents (M_age=15.78, SD=1.08), the extent to which ERP amplitude and latency variables measuring reward anticipation and response (1) differentiate, in age- and sex-matched subsamples, (i) youth with vs. without ADHD, (ii) youth at-risk for vs. not at-risk for ADHD, and, in the with ADHD subsample, (iii) youth with the inattentive vs. the hyperactive/impulsive (H/I) and combined presentations. We further examined the extent to which ERP variables (2) predict, in the ADHD subsample, substance use (i) concurrently and (ii) prospectively at 18-month follow-up. Linear support vector machine analyses indicated ERPs weakly differentiate youth with/without (65%) - and at-risk for/not at-risk for (63%) - ADHD but better differentiate ADHD presentations (78%). Regression analyses showed in adolescents with ADHD, ERPs explain a considerable proportion of variance (50%) in concurrent alcohol use and, controlling for concurrent marijuana and tobacco use, explain a considerable proportion of variance (87 and 87%) in, and predict later marijuana and tobacco use. Findings are consistent with the dual-pathway model of ADHD. Results also highlight limitations of a dichotomous, syndromic classification and indicate differences in neural reinforcement sensitivity are a promising ADHD prognostic biomarker.

The association between attention deficit hyperactivity disorder (ADHD) and smoking experience or exposure to environmental tobacco smoke among children and adolescents

INTRODUCTION

Direct and indirect smoking exposure is highly related to mental health in children. This study aimed to identify the association between exposure to smoking or secondhand smoke (SHS) and attention deficit hyperactivity disorder (ADHD).

METHODS

We used data from the Korean National Health and Nutrition Examination Survey (KNHANES) from 2007 to 2019, including variables such as diagnosed ADHD, smoking status, SHS, and urine cotinine levels among children and adolescents. We estimated the risk of ADHD according to smoking or SHS exposure in various exposure groups using adjusted logistic or linear regression models.

RESULTS

Among 16434 participants, 133 children were diagnosed with ADHD (0.8%). Of these, 58 (43.6%) were aged <12 years and 75 (56.3%) were aged ≥12 years. Smoking was significantly associated with ADHD (crude odds ratio, OR=1.48; 95% CI: 1.14-3.26 and adjusted odds ratio, AOR=1.22; 95% CI: 1.02- 1.64). SHS exposure and ADHD were attenuated after adjustment (OR=2.42; 95% CI: 1.08-4.02; AOR=1.42; 95% CI: 0.86-2.64) in the logistic regression model. Smoking history was statistically associated with a younger age of ADHD diagnosis in the linear regression model.

CONCLUSIONS

Smoking and the amount of smoking among children and adolescents was associated with ADHD.

Cardiovascular risk factors in attention-deficit/hyperactivity disorder: A family design study of Swedish conscripts

OBJECTIVE

(1) investigate the associations of attention-deficit/hyperactivity disorder (ADHD) with systolic and diastolic blood pressure, resting heart rate, pulse pressure (PP), physical fitness, and BMI; (2) explore whether cardiovascular risk factors and ADHD share genetic and environmental influences; (3) assess if pharmacological treatment for ADHD influences these associations.

METHODS

We identified 395,978 individuals born between 1973 and 1991 who had military conscription examinations at a mean age of 18.3 years (SD = 0.57) and their full-siblings within the same cohort (N = 208,060) by linking population-based registers in Sweden.

RESULTS

Significantly increased risk of ADHD was observed in individuals with low systolic blood pressure (SBP) and PP, low physical fitness, and in those who had overweight or obesity after adjustments (adjusted Odds Ratio [OR] ranging from 1.10 to 1.45). Full siblings of individuals with low SBP, low physical fitness, and obesity were more likely to receive an ADHD diagnosis compared to full siblings without those risk factors (OR ranging from 1.17 to 1.31). Additionally, analyses showed robust associations between ADHD and low SBP, low physical fitness, and obesity, even in ADHD medication-naïve individuals.

CONCLUSIONS

Individuals with several cardiovascular risk factors are more often diagnosed with ADHD, regardless of psychiatric comorbidity. These association are not explained by ADHD pharmacotherapy, rather, they are in part due to shared familial risk factors.

Smoking cessation among people with mental illness: A South African perspective

Tobacco use is recognised as a serious, worldwide public health concern. Smoking cessation is of great interest across a wide range of medical specialities, including family medicine. However, smoking cessation among people with mental illness (PWMI) has attracted scant attention in South African literature. This is despite PWMI suffering disproportionately from the damages of tobacco. The harms of smoking are not limited to physical health but extend to mental health. This article discusses the need for multifaceted smoking cessation treatments for PWMI in the public health sector, taking into consideration the prevalence and unique drivers of smoking in this population. A brief overview of patterns of tobacco use, associated harms and smoking cessation interventions in South Africa is given; all within the context of mental illness.

The therapeutic potential of exercise and caffeine on attention-deficit/hyperactivity disorder in athletes

Attention-deficit/hyperactivity disorder (ADHD) is characterized by evident and persistent inattention, hyperactivity, impulsivity, and social difficulties and is the most common childhood neuropsychiatric disorder, and which may persist into adulthood. Seventy to 80% of children and adults with ADHD are treated with stimulant medication, with positive response rates occurring for both populations. Medicated ADHD individuals generally show sustained and improved attention, inhibition control, cognitive flexibility, on-task behavior, and cognitive performance. The ethics of ADHD medication use in athletics has been a debated topic in sport performance for a long time. Stimulants are banned from competition in accordance with World Anti-Doping Association and National Collegiate Athletic Association regulations, due to their ability to not only enhance cognitive performance but also exercise performance. Limited research has been conducted looking at the differences in exercise performance variables in unmedicated ADHD verses medicated ADHD. Not all ADHD athletes choose stimulant medication in their treatment plan due to personal, financial, or other reasons. Non-stimulant treatment options include non-stimulant medication and behavioral therapy. However, the use of caffeinated compounds and exercise has both independently been shown to be effective in the management of ADHD symptoms in human studies and animal models. This mini review will discuss the effect of exercise and caffeine on neurobehavioral, cognitive, and neurophysiological factors, and exercise performance in ADHD athletes, and whether exercise and caffeine should be considered in the treatment plan for an individual with ADHD.

Longer screen time utilization is associated with the polygenic risk for Attention-deficit/hyperactivity disorder with mediation by brain white matter microstructure

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) has been reported to be associated with longer screen time utilization (STU) at the behavioral level. However, whether there are shared neural links between ADHD symptoms and prolonged STU is not clear and has not been explored in a single large-scale dataset.

METHODS

Leveraging the genetics, neuroimaging and behavioral data of 11,000+ children aged 9-11 from the Adolescent Brain Cognitive Development cohort, this study investigates the associations between the polygenic risk and trait for ADHD, STU, and white matter microstructure through cross-sectionally and longitudinal analyses.

FINDINGS

Children with higher polygenic risk scores for ADHD tend to have longer STU and more severe ADHD symptoms. Fractional anisotropy (FA) values in several white matter tracts are negatively correlated with both the ADHD polygenic risk score and STU, including the inferior frontal-striatal tract, inferior frontal-occipital fasciculus, superior longitudinal fasciculus and corpus callosum. Most of these tracts are linked to visual-related functions. Longitudinal analyses indicate a directional effect of white matter microstructure on the ADHD scale, and a bi-directional effect between the ADHD scale and STU. Furthermore, reduction of FA in several white matter tracts mediates the association between the ADHD polygenic risk score and STU.

INTERPRETATION

These findings shed new light on the shared neural overlaps between ADHD symptoms and prolonged STU, and provide evidence that the polygenic risk for ADHD is related, via white matter microstructure and the ADHD trait, to STU.

FUNDING

This study was mainly supported by NSFC and National Key R&D Program of China.

Fibroblast growth factor 21 associating with serotonin and dopamine in the cerebrospinal fluid predicts impulsivity in healthy subjects

BACKGROUND

Impulsivity is more commonly reported in subjects with mental disorders compared to healthy subjects, suggesting a potential application of impulsivity in predicting impulsivity-related mental disorders. However, no biomarker of impulsivity available so far. This study explored the association between cerebrospinal fluid (CSF) fibroblast growth factor 21 (FGF21), a key hormonal mediator of the stress response, and impulsivity in healthy subjects.

METHODS

A total of 126 healthy persons subjected to surgery of anterior cruciate ligament were recruited in the present study. The impulsiveness of the subjects was evaluated by the Chinese version of the Barratt Impulsiveness Scale (BIS)-11 before surgery. CSF and blood samples of the subjects were collected before spinal anesthesia for surgery. The levels of FGF21, serotonin and dopamine in CSF and the level of FGF21 in blood of the subjects were measured by ELISA using commercial kits.

RESULTS

Negative correlations were found between BIS-11 total score and either FGF21, serotonin or dopamine in CSF. However, BIS-11 total score was not correlated with FGF21 in blood. In addition, FGF21 was positively correlated with serotonin and dopamine in CSF, respectively. Multivariable linear regression models indicated that the decrease of FGF21 level associating with the decrease of serotonin and dopamine level in CSF contributed to the higher impulsivity. Furthermore, receiver operating characteristic curve (ROC) analysis indicated an important role of CSF FGF21 predicting high impulsivity.

CONCLUSIONS

FGF21, serotonin and dopamine in CSF associate with impulsivity in opposite directions. The decrease of CSF FGF21 is related to higher impulsivity, and indicate that CSF FGF21 may predict impulsivity in healthy subjects.

Effects of an Adenosine A2A Receptor Antagonist on Striatal Dopamine D2-Type Receptor Availability: A Randomized Control Study Using Positron Emission Tomography

Introduction: Altered dopaminergic neurotransmission, especially in the functioning of dopamine D2-type receptors, is considered central to the etiology of a variety of neuropsychiatric disorders. In particular, individuals with substance use disorders have been consistently observed to exhibit lower D2-type receptor availability (quantified as binding potential; BPND) using positron emission tomography (PET). Upregulation of D2-type receptor density thus may therefore provide a therapeutic effect for substance use disorders. Importantly, in vitro studies reveal that D2 receptors coexist with adenosine 2A (A2A) receptors to form the highest density of heteromers in the whole striatum, and there is a functional interaction between these two receptors. As such, blockade of A2A receptor's function may prevent D2 receptor downregulation, yet no study has currently examined this hypothesis in humans. Methods and Analysis: This double-blind, randomized controlled trial aims to evaluate the effect of the A2A receptor antagonist istradefylline (compared to placebo) on both dopamine D2-type receptor availability in the human brain and on neuropsychological measurements of impulsivity. It is hypothesized that istradefylline will both increase striatal D2-type BPND and improve control of impulsivity more than placebo. Forty healthy participants, aged 20-65 with no history of psychiatric or neurological disorders, will be recruited and randomized into two groups and will undergo [11C]raclopride PET, once before and once after administration of either 40 mg/day istradefylline or placebo for 2 weeks. Neuropsychological measurements will be administered on the same days of the PET scans. Ethics and Dissemination: The study protocol was approved by the Certified Review Boards (CRB) of National Center of Neurology and Psychiatry (CR18-011) and prospectively registered with the Japan Registry of Clinical Trials (jRCTs031180131; https://jrct.niph.go.jp/latest-detail/jRCTs031180131). The findings of this study will be disseminated through peer reviewed scientific journals and conferences. Clinical Trial Registration:www.ClinicalTrials.gov, identifier jRCTs031180131.

Monoaminergic hypo- or hyperfunction in adolescent and adult attention-deficit hyperactivity disorder?

Disturbances of dopamine (DA), serotonin (5-HT) and/or norepinephrine (NE) functions are implied in attention-deficit hyperactivity disorder (ADHD). However, the precise cortical and subcortical mechanisms are still not fully understood. In the present survey, we conducted a PUBMED search, which provided 37 in vivo investigations with PET and SPECT on 419 ADHD patients and 490 controls. The retrospective analysis revealed increased striatal DA transporter (DAT) in adolescent as well as adult medication-naïve and not acutely medicated patients. In acutely medicated adults, DAT was not different from controls. Midbrain DAT was normal in adults, but decreased in adolescents. Striatal D₂ receptor (R) binding was normal in both adolescents (not acutely medicated) and adults (acutely medicated and not acutely medicated). In medication-naïve adults, DA synthesis was decreased in putamen and amygdala, but normal in the whole striatum and midbrain. In not acutely medicated adults, DA synthesis was reduced in putamen, whole striatum, prefrontal cortex, frontal cortex, amygdala and midbrain, whereas, in adolescents, no regional differences were observed. In adult (not acutely medicated) subjects, cingulate D₁R was reduced. 5-HT transporter (SERT) binding was decreased in striatum and thalamus, but normal in midbrain, neocortex and limbic regions, whereas, in medication-naïve adults, SERT was diminished in striatum and midbrain, but normal in thalamus and neocortex. The findings suggest transient stages of synaptic DA shortage as well as DA surplus in individual brain regions, which elicit presynaptic as well as postsynaptic compensatory mechanisms, striving to attain functional homeostasis. Thereby, it remains a matter of debate, whether ADHD may be characterized by a general hypo- or hyperactivity of DA and/or 5-HT function.

Dopamine, Prediction Error and Beyond

A large body of work has linked dopaminergic signaling to learning and reward processing. It stresses the role of dopamine in reward prediction error signaling, a key neural signal that allows us to learn from past experiences, and that facilitates optimal choice behavior. Latterly, it has become clear that dopamine does not merely code prediction error size but also signals the difference between the expected value of rewards, and the value of rewards actually received, which is obtained through the integration of reward attributes such as the type, amount, probability and delay. More recent work has posited a role of dopamine in learning beyond rewards. These theories suggest that dopamine codes absolute or unsigned prediction errors, playing a key role in how the brain models associative regularities within its environment, while incorporating critical information about the reliability of those regularities. Work is emerging supporting this perspective and, it has inspired theoretical models of how certain forms of mental pathology may emerge in relation to dopamine function. Such pathology is frequently related to disturbed inferences leading to altered internal models of the environment. Thus, it is critical to understand the role of dopamine in error-related learning and inference.

Electronic Cigarettes Associated With Incident and Polysubstance Use Among Youth

PURPOSE

Electronic cigarette (e-cigarette) use has increased exponentially among the youth in the United States and may increase the incidence of substance use.

METHODS

Youth participants (12-17 years) were surveyed through the Population Assessment of Tobacco and Health study over a three-year time period. Youth with any baseline substance use or diagnosis of an attention deficit disorder were excluded from the analysis. Multivariable logistic regressions were used to assess the association between e-cigarette use at Wave 1 and incident substance use (marijuana, painkillers, sedatives, or tranquilizers and Ritalin/Adderall) and polysubstance use at Wave 2 or 3, and marijuana use in the electronic nicotine device at Wave 3.

RESULTS

Baseline ever e-cigarette users who had no history of marijuana, nonprescribed drugs and illicit substance use in Wave 1 had increased odds of reporting incident use of marijuana (odds ratio 2.59, 95% confidence interval: 1.90-3.52), nonprescribed Ritalin/Adderall use (1.89, 1.09-3.28), or polysubstance use (2.09, 1.43-3.05) in Wave 2 or 3 compared to never e-cigarette users. They were also more likely to report use of marijuana in the electronic nicotine product (2.26, 1.56-3.27) in Wave 3 compared to never e-cigarette users. There was no statistically significant association between baseline e-cigarette use and incident use of painkillers, sedatives, or tranquilizers in Wave 2 or 3 (1.21, .79-1.87).

CONCLUSIONS

E-cigarette use is associated with incident use of marijuana, marijuana in electronic nicotine devices, Ritalin/Adderall, and polysubstance use but not painkillers, sedatives, or tranquilizers. Results indicate that e-cigarettes are associated with subsequent additional risky health behaviors in youth.

Visual statistical learning and integration of perceptual priors are intact in attention deficit hyperactivity disorder

Background

Deficits in visual statistical learning and predictive processing could in principle explain the key characteristics of inattention and distractibility in attention deficit hyperactivity disorder (ADHD). Specifically, from a Bayesian perspective, ADHD may be associated with flatter likelihoods (increased sensory processing noise), and/or difficulties in generating or using predictions. To our knowledge, such hypotheses have never been directly tested.

Methods

We here test these hypotheses by evaluating whether adults diagnosed with ADHD (n = 17) differed from a control group (n = 30) in implicitly learning and using low-level perceptual priors to guide sensory processing. We used a visual statistical learning task in which participants had to estimate the direction of a cloud of coherently moving dots. Unbeknown to the participants, two of the directions were more frequently presented than the others, creating an implicit bias (prior) towards those directions. This task had previously revealed differences in other neurodevelopmental disorders, such as autistic spectrum disorder and schizophrenia.

Results

We found that both groups acquired the prior expectation for the most frequent directions and that these expectations substantially influenced task performance. Overall, there were no group differences in how much the priors influenced performance. However, subtle group differences were found in the influence of the prior over time.

Conclusion

Our findings suggest that the symptoms of inattention and hyperactivity in ADHD do not stem from broad difficulties in developing and/or using low-level perceptual priors.

Transgenerational transmission of behavioral phenotypes produced by exposure of male mice to saccharin and nicotine

The use of non-nutritive sweeteners such as saccharin is widely prevalent. Although saccharin is considered safe for human consumption, it produces behavioral changes in experimental animals. We report that saccharin’s behavioral effects are much more pervasive than currently recognized. In a mouse model, saccharin exposure produced motor impulsivity not only in the saccharin-exposed males but also in their offspring. In addition, the offspring showed locomotor hyperactivity and working memory deficit not observed in fathers. Spermatazoal DNA was hypermethylated in the saccharin-exposed fathers, especially at dopamine receptor promoter regions, suggesting that epigenetic modification of germ cell DNA may mediate transgenerational transmission of behavioral phenotypes. Dopamine’s role in hyperactivity was further highlighted by the finding that the stimulant drug methylphenidate mitigated the hyperactivity. Nicotine is another substance that is widely used. Its use via smokeless tobacco products, some of which contain saccharin, is on the rise contributing to concerns about adverse outcomes of co-exposure to saccharin and nicotine. We found that co-exposure of male mice to saccharin and nicotine produced significant behavioral impairment in their offspring. Thus, our data point to potential adverse neurobehavioral consequences of exposure to saccharin alone or saccharin and nicotine for the exposed individuals and their descendants.

Early substance use in the pathway from childhood attention-deficit/hyperactivity disorder (ADHD) to young adult substance use: Evidence of statistical mediation and substance specificity

This study tested whether early and developmentally atypical substance use mediates risk for adult substance use among children with attention-deficit/hyperactivity disorder (ADHD), and whether that risk is substance-specific. Participants were children with ADHD previously enrolled in a randomized controlled trial (RCT), and a demographically similar non-ADHD group, assessed at 2 through 16 years after the original RCT baseline. Self-reports of heavy drinking, marijuana use, daily smoking, and other illicit drug use were collected at follow-ups to establish atypically early and frequent use. Models estimated statistically mediated effects of childhood ADHD on adult substance use via early substance involvement, with planned comparisons to evaluate substance specificity. Results supported the mediation hypothesis, showing that childhood ADHD was associated with more frequent adult substance use via early substance involvement for marijuana, cigarettes, illicit drugs, and to a lesser extent, alcohol. Mediation was not escalated by comorbid childhood conduct disorder or oppositional defiant disorder except for early use of nonmarijuana illicit drugs. Substance-specificity in the mediational pathway was largely absent except for cigarette use, where ADHD-related early smoking most strongly predicted adult daily smoking. Findings from this study provide new evidence that atypically early substance use associated with childhood ADHD signals important cross-drug vulnerability by early adulthood, but cigarette use at a young age is especially associated with increased risk for habitual (daily) smoking specifically. Efforts to prevent, delay, or reduce substance experimentation should occur early and focus on factors relevant to multiple drugs of abuse in this at-risk population. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Electrochemical detection of paracetamol and dopamine molecules using nano-particles of cobalt ferrite and manganese ferrite modified with graphite

Some electrodes for efficient detection of paracetamol and dopamine were developed from nano sized material of cobalt ferrite (np-CoFe₂O₄) and manganese ferrite (np-MnFe₂O₄). These oxides were synthesized by combustion method using cobalt nitrate, manganese acetate and ferric nitrate as precursors in the presence of sugar and ethanolamine. The crystallite size, shape and morphology of nano material were characterized by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS) techniques. The crystallite sizes of synthesized nano-particles (nps) were in the range from 10 to 12 nm (calculated using Debye-Scherrer equation) with cubic crystal system. These particles were utilized as electrode modified with graphite for simultaneous detection of paracetamol and dopamine through cyclic voltammetry and Differential pulse voltammetry techniques and was found to be superior to reported literatures. The minimum detection limit of paracetamol and dopamine at CoFe₂O₄/GP electrode were 250 nM and 350 nM while at MnFe₂O₄/GP electrode it was 300 nM and 400 nM, respectively. Both the electrodes exhibited the linearity range from3 μM to 200 μM & 3 μM-160 μM for paracetamol and 3 μM-180 μM & 5 μM to 200 for dopamine, respectively. Two oxidation peaks of paracetamol and dopamine were well separated in phosphate buffer (pH = 6) in mixture with 100 mVs^-1 and 50 mVs^-1 scan rate for cyclic voltammetry and Differential pulse voltammetry, respectively. Both the electrodes demonstrated satisfactory results in real samples of paracetamol and dopamine.

Dissociation of impulsivity and aggression in mice deficient for the ADHD risk gene Adgrl3: Evidence for dopamine transporter dysregulation

Adhesion G protein-coupled receptor L3 (ADGRL3, LPHN3) has putative roles in neuronal migration and synapse function. Various polymorphisms in ADGRL3 have been linked with an increased risk of attention deficit/hyperactivity disorder (ADHD). In this study, we examined the characteristics of Adgrl3-deficient mice in multiple behavioural domains related to ADHD: locomotive activity, impulsivity, gait, visuospatial and recognition memory, sociability, anxiety-like behaviour and aggression. Additionally, we investigated the effect of Adgrl3-depletion at the transcriptomic level by RNA-sequencing three ADHD-relevant brain regions: prefrontal cortex (PFC), hippocampus and striatum. Adgrl3^-/- mice show increased locomotive activity across all tests and subtle gait abnormalities. These mice also show impairments across spatial memory and learning domains, alongside increased levels of impulsivity and sociability with decreased aggression. However, these alterations were absent in Adgrl3^+/- mice. Across all brain regions tested, the numbers of genes found to exhibit differential expression was relatively small, indicating a specific pathway of action, rather than a broad neurobiological perturbation. Gene-set analysis of differential expression in the PFC detected a number of ADHD-relevant pathways including dopaminergic synapses as well as cocaine and amphetamine addiction. The Slc6a3 gene coding for the dopamine transporter was the most dysregulated gene in the PFC. Unexpectedly, several neurohormone/peptides which are typically only expressed in the hypothamalus were found to be dysregulated in the striatum. Our study further validates Adgrl3 constitutive knockout mice as an experimental model of ADHD while providing neuroanatomical targets for future studies involving ADGRL3 modified models. This article is part of the Special Issue entitled 'Current status of the neurobiology of aggression and impulsivity'.

Iron and manganese-related CNS toxicity: mechanisms, diagnosis and treatment

INTRODUCTION

Iron (Fe) and manganese (Mn) are essential nutrients for humans. They act as cofactors for a variety of enzymes. In the central nervous system (CNS), these two metals are involved in diverse neurological activities. Dyshomeostasis may interfere with the critical enzymatic activities, hence altering the neurophysiological status and resulting in neurological diseases. Areas covered: In this review, the authors cover the molecular mechanisms of Fe/Mn-induced toxicity and neurological diseases, as well as the diagnosis and potential treatment. Given that both Fe and Mn are abundant in the earth crust, nutritional deficiency is rare. In this review the authors focus on the neurological disorders associated with Mn and Fe overload. Expert commentary: Oxidative stress and mitochondrial dysfunction are the primary molecular mechanism that mediates Fe/Mn-induced neurotoxicity. Although increased Fe or Mn concentrations have been found in brain of patients, it remains controversial whether the elevated metal amounts are the primary cause or secondary consequence of neurological diseases. Currently, treatments are far from satisfactory, although chelation therapy can significantly decrease brain Fe and Mn levels. Studies to determine the primary cause and establish the molecular mechanism of toxicity may help to adapt more comprehensive and satisfactory treatments in the future.

Frontostriatal Dysfunction During Decision Making in Attention-Deficit/Hyperactivity Disorder and Obsessive-Compulsive Disorder

Background

The aim of the current paper is to provide the first comparison of computational mechanisms and neurofunctional substrates in adolescents with attention-deficit/hyperactivity disorder (ADHD) and adolescents with obsessive-compulsive disorder (OCD) during decision making under ambiguity.

Methods

Sixteen boys with ADHD, 20 boys with OCD, and 20 matched control subjects (12–18 years of age) completed a functional magnetic resonance imaging version of the Iowa Gambling Task. Brain activation was compared between groups using three-way analysis of covariance. Hierarchical Bayesian analysis was used to compare computational modeling parameters between groups.

Results

Patient groups shared reduced choice consistency and relied less on reinforcement learning during decision making relative to control subjects, while adolescents with ADHD alone demonstrated increased reward sensitivity. During advantageous choices, both disorders shared underactivation in ventral striatum, while OCD patients showed disorder-specific underactivation in the ventromedial orbitofrontal cortex. During outcome evaluation, shared underactivation to losses in patients relative to control subjects was found in the medial prefrontal cortex and shared underactivation to wins was found in the left putamen/caudate. ADHD boys showed disorder-specific dysfunction in the right putamen/caudate, which was activated more to losses in patients with ADHD but more to wins in control subjects.

Conclusions

The findings suggest shared deficits in using learned reward expectancies to guide decision making, as well as shared dysfunction in medio-fronto-striato-limbic brain regions. However, findings of unique dysfunction in the ventromedial orbitofrontal cortex in OCD and in the right putamen in ADHD indicate additional, disorder-specific abnormalities and extend similar findings from inhibitory control tasks in the disorders to the domain of decision making under ambiguity.

Stress, attention deficit hyperactivity disorder (ADHD) symptoms and tobacco smoking: The i-Share study

BACKGROUND

The contribution of mental health to the risk of smoking is increasingly acknowledged but still insufficiently studied during the key period of student life. In particular, the simultaneous action of stress and Attention Deficit Hyperactivity Disorder (ADHD) symptoms on the risk of smoking remains poorly understood.

AIMS

To assess the effects of stress and ADHD symptoms on tobacco smoking.

METHOD

Multivariate modeling was conducted on the French i-Share study (n=8110, median age 20.3 years, 74.8% females, 32.9% regular/occasional smokers) to evaluate the associations between stress, ADHD symptoms and tobacco smoking, adjusting for potential family/socio-demographic confounders.

RESULTS

Students with high levels of stress were more likely to smoke>10 cigarettes/day (adjusted odds ratio (aOR): 1.48, 95% CI: 1.12-1.96) than those with low levels of stress. Students with high levels of ADHD symptoms were more likely to smoke>10 cigarettes/day (aOR: 2.08, 95% CI: 1.58-2.75) than those with low levels of ADHD symptoms.

CONCLUSIONS

Stress and ADHD contribute independently to the risk of smoking. Interventions targeting each condition are likely to reduce the burden of tobacco use in students.

Predictors of Nicotine Dependence in Adolescents: Symptoms of Bipolar Disorder and Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

Bipolar disorder (BD) and attention-deficit/hyperactivity disorder (ADHD) have been associated with the use of cigarettes, but little is known about the impact of the subthreshold symptoms of BD or ADHD on the course of nicotine dependence. Identifying the links is essential for elucidating the pathway and supporting the development of nicotine prevention strategies for adolescents.

METHODS

Participants (n = 3322) aged 15-17 years completed the Chinese version of the ADHD Self-Report Scale and the Mood Disorder Questionnaire. The modified Fagerström Tolerance Questionnaire was completed to measure their nicotine use or dependence. Mediation analyses were performed to explore the relationship of two predictors.

RESULTS

The prevalence rates of cigarette smoking and nicotine dependence in this study were 14.4% and 2.3%, respectively. Male gender (odds ratio [OR] 2.30; 95% confidence interval [CI] 1.60-3.30), subclinical symptoms of ADHD (OR 1.34; 95% CI 1.04-1.71), clinical symptoms of ADHD (OR 1.69; 95% CI 1.08-2.66), and symptoms of BD (OR 1.59; 95% CI1.09 to 2.32) were associated with nicotine use. Male gender (OR 4.60; 95% CI 1.41-14.98) and symptoms of BD (OR 6.14; 95% CI 3.37-11.18), but not symptoms of ADHD, were associated with nicotine dependence. In mediation analyses, we found that the effect of ADHD symptoms was no longer significant after controlling for symptoms of BD, and the mediation ratio (P_M) was 0.39.

CONCLUSIONS

Our findings suggest that mood disturbances other than symptoms of ADHD are more likely to be a key predictor of nicotine dependence among adolescents. The conclusions may improve our understanding of the course of nicotine dependence and help to promote potential health policy for nicotine control among youths.

Attention deficit-hyperactivity disorder is associated with reduced blood pressure and serum vitamin D levels: results from the nationwide German Health Interview and Examination Survey for Children and Adolescents (KiGGS)

Alterations in blood pressure in attention-deficit/hyperactivity disorder (ADHD), specifically during dopaminergic stimulant intake, are not fully understood. It has been reported that vitamin D deficiency might modify dopaminergic pathways and thus influence ADHD symptoms. Using data from the nationwide German Health Interview and Examination Survey for Children and Adolescents (KiGGS) study, we compared blood pressure and vitamin D levels in healthy controls to both diagnosed ADHD patients and suspected ADHD subjects, as defined by a value of ≥7 on the hyperactivity-inattention subscale of the Strengths and Difficulties Questionnaire. In a total cohort of n = 6922 study participants aged 11-17 years, mean arterial blood pressure was significantly higher in controls (86.7 ± 8.2 mmHg) than in the two groups of confirmed (85.5 ± 7.8 mmHg, p = 0.004, n = 430) and suspected ADHD patients (84.6 ± 8.2, p < 0.001, n = 399). In addition, we found an inverse association between vitamin D and blood pressure in both ADHD groups (p < 0.003). Regression analyses adjusted for age, sex, body-mass index, psychotropic medication use, and serum vitamin D levels confirmed that low blood pressure was a significant and independent predictor of ADHD. Furthermore, we observed that vitamin D mediated the effect of systolic blood pressure on ADHD diagnosis (b = 0.007, 95 % confidence interval [CI] 0.001-0.013, p = 0.021, R ² = 0.050). In a large and representative national sample of German adolescents, we found a significant association between low blood pressure and ADHD symptoms. In addition, we observed that circulating vitamin D mediated the inverse relation between blood pressure and ADHD, although the effect size was very low. These findings highlight the role of dysregulated pathways of the autonomic nervous system in ADHD.

Strategies to promote smoking cessation among adolescents

In recent years, youth have been exposed to a broader spectrum of tobacco products including smokeless tobacco, hookah (water pipe) and e-cigarettes. Despite active local, provincial/territorial and national prevention strategies and legislated controls, thousands of teenagers develop an addiction to tobacco products each year. Current and available smoking cessation interventions for youth have the potential to help teens stop smoking and, as a result, greatly reduce Canada's health burden in the future. Paediatricians and health care professionals can play a key role in helping teens make informed decisions related to tobacco consumption and cessation. This practice point presents the evidence and rationales for smoking cessation interventions which have been studied in youth specifically, such as individual counselling, psychological support, nicotine replacement therapy, bupropion and varenicline. Interventions for which limited or conflicting data exist are also discussed.

Symbolic dynamics of heart rate variability — a promising tool to investigate cardiac sympathovagal control in attention deficit/hyperactivity disorder (ADHD)?

We aimed to evaluate complex cardiac sympathovagal control in attention deficit/hyperactivity disorder (ADHD) by using heart rate variability (HRV) nonlinear analysis — symbolic dynamics. We examined 29 boys with untreated ADHD and 25 healthy boys (age 8–13 years). ADHD symptoms were evaluated by ADHD-RS-IV scale. ECG was recorded in 3 positions: baseline supine position, orthostasis, and clinostasis. Symbolic dynamics indices were used for the assessment of complex cardiac sympathovagal regulation: normalised complexity index (NCI), normalised unpredictability index (NUPI), and pattern classification measures (0V%, 1V%, 2LV%, 2UV%). The results showed that HRV complexity was significantly reduced at rest (NUPI) and during standing position (NCI, NUPI) in ADHD group compared to controls. Cardiac-linked sympathetic index 0V% was significantly higher during all posture positions and cardiovagal index 2LV% was significantly lower to standing in boys suffering from ADHD. Importantly, ADHD symptom inattention positively correlated with 0V%, and negatively correlated with NCI, NUPI. Concluding, symbolic dynamics revealed impaired complex neurocardiac control characterised by potential cardiac beta-adrenergic overactivity and vagal deficiency at rest and to posture changes in boys suffering from ADHD that is correlated with inattention. We suggest that symbolic dynamics indices could represent promising cardiac biomarkers in ADHD.

Specific cognitive-neurophysiological processes predict impulsivity in the childhood attention-deficit/hyperactivity disorder combined subtype

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent neuropsychiatric disorders in childhood. Besides inattention and hyperactivity, impulsivity is the third core symptom leading to diverse and serious problems. However, the neuronal mechanisms underlying impulsivity in ADHD are still not fully understood. This is all the more the case when patients with the ADHD combined subtype (ADHD-C) are considered who are characterized by both symptoms of inattention and hyperactivity/impulsivity.

METHOD

Combining high-density electroencephalography (EEG) recordings with source localization analyses, we examined what information processing stages are dysfunctional in ADHD-C (n = 20) compared with controls (n = 18).

RESULTS

Patients with ADHD-C made more impulsive errors in a Go/No-go task than healthy controls. Neurophysiologically, different subprocesses from perceptual gating to attentional selection, resource allocation and response selection processes are altered in this patient group. Perceptual gating, stimulus-driven attention selection and resource allocation processes were more pronounced in ADHD-C, are related to activation differences in parieto-occipital networks and suggest attentional filtering deficits. However, only response selection processes, associated with medial prefrontal networks, predicted impulsive errors in ADHD-C.

CONCLUSIONS

Although the clinical picture of ADHD-C is complex and a multitude of processing steps are altered, only a subset of processes seems to directly modulate impulsive behaviour. The present findings improve the understanding of mechanisms underlying impulsivity in patients with ADHD-C and might help to refine treatment algorithms focusing on impulsivity.

Nicotine and the adolescent brain

Adolescence encompasses a sensitive developmental period of enhanced clinical vulnerability to nicotine, tobacco, and e-cigarettes. While there are sociocultural influences, data at preclinical and clinical levels indicate that this adolescent sensitivity has strong neurobiological underpinnings. Although definitions of adolescence vary, the hallmark of this period is a profound reorganization of brain regions necessary for mature cognitive and executive function, working memory, reward processing, emotional regulation, and motivated behavior. Regulating critical facets of brain maturation are nicotinic acetylcholine receptors (nAChRs). However, perturbations of cholinergic systems during this time with nicotine, via tobacco or e-cigarettes, have unique consequences on adolescent development. In this review, we highlight recent clinical and preclinical data examining the adolescent brain's distinct neurobiology and unique sensitivity to nicotine. First, we discuss what defines adolescence before reviewing normative structural and neurochemical alterations that persist until early adulthood, with an emphasis on dopaminergic systems. We review how acute exposure to nicotine impacts brain development and how drug responses differ from those seen in adults. Finally, we discuss the persistent alterations in neuronal signaling and cognitive function that result from chronic nicotine exposure, while highlighting a low dose, semi-chronic exposure paradigm that may better model adolescent tobacco use. We argue that nicotine exposure, increasingly occurring as a result of e-cigarette use, may induce epigenetic changes that sensitize the brain to other drugs and prime it for future substance abuse.