Biochemical and genetic analyses of childhood attention deficit/hyperactivity disorder

Using varied technological agents-assisted simultaneous prompting for teaching discrete skills to children with developmental disabilities

This study examines the effectiveness of combining simultaneous prompting method with small group teaching through computer projection, SMART board, tablet computer and humanoid robot to teach discrete skills to children with developmental disabilities (CDD). The study included 14 CDD aged 10-15. It utilizes a multiple probe design across behaviors and probe conditions and replicates them across subjects. Each participant is taught discrete skills within a small group teaching arrangement. The study includes daily probes, full probes, teaching sessions, generalization, and follow-up sessions. It also collects interobserver reliability and application reliability data. Graphical analysis demonstrates the effectiveness of computer-based simultaneous prompting incorporating different technologies in a small group teaching setting. Additionally, we examined differences in children's responses to different technological agents in teaching discrete skills to children with developmental disabilities. The study provided preliminary data on which of these agents is best. The results demonstrate its effectiveness by showing that participants maintained the learned behaviors and applied them to a variety of tools, equipment, and individuals in the first, third, and fourth weeks after the intervention. Additionally, the study highlights the subjects' high accuracy in acquiring behavior through observational learning. Finally, simple humanoid robots, tablets, smart SMART boards, and computer projections have been effective in teaching discrete skills to CDD, respectively.

Serum Biomarker Analysis in Pediatric ADHD: Implications of Homocysteine, Vitamin B12, Vitamin D, Ferritin, and Iron Levels

The current diagnosis of attention deficit hyperactivity disorder (ADHD) is based on history, clinical observation, and behavioral tests. There is a high demand to find biomarkers for the diagnosis of ADHD. The aim of this study is to analyze the serum profiles of several biomarkers, including homocysteine (Hcy), vitamin B12, vitamin D, ferritin, and iron, in a cohort of 133 male subjects (6.5-12.5 years), including 67 individuals with an ADHD diagnosis based on DSM-V criteria and 66 age-matched healthy boys (healthy controls, HC). Assessments for ADHD included the Iowa Conners' Teacher Rating Scale (CPRS) and the ADHDT test, as well as cognitive assessments using the Wechsler Intelligence Scale for Children-Revised (WISC-R) and the TROG-2 language comprehension test. Hcy and iron were quantified using spectrophotometry, while vitamin B12 and total 25-hydroxy vitamin D levels were determined using an electrochemiluminescence immunoassay (ECLIA) and ferritin was measured using a particle-enhanced immunoturbidimetric assay. The results showed significantly increased Hcy levels and decreased vitamin B12 levels in ADHD patients compared to HCs. Multiple logistic regression analysis indicated that Hcy is a potential prognostic indicator for ADHD. These results suggest that elevated homocysteine and decreased vitamin B12 may serve as markers for the diagnosis and prognosis of ADHD.

Magnesium status and attention deficit hyperactivity disorder (ADHD): A meta-analysis

Current research suggests conflicting evidence surrounding the association between serum magnesium levels and the diagnosis of attention deficit hyperactivity disorder (ADHD). This systematic review and meta-analysis aims to explore, summarize and quantify the published literature addressing this topic. We conducted an exhaustive literature search on Scopus and PubMed for all the relevant observational studies published up to August 2018. A meta-analysis using a random-effects model was used to summarize the overall association between serum magnesium level and ADHD from the available data. We identified seven studies which reported the mean and standard deviation (SD) of magnesium concentration in both ADHD and control groups. The random-effects meta-analysis showed that subjects with ADHD had 0.105 mmol/l (95% CI: -0.188, -0.022; P < 0.013) lower serum magnesium levels compared with to their healthy controls. Moreover, we observed striking and statistically significant heterogeneity among the included studies (I² = 96.2%, P = 0.0103). The evidence from this meta-analysis supports the theory that an inverse relationship between serum magnesium deficiency and ADHD exists. High heterogeneity amongst the included studies suggests that there is a residual need for observational and community-based studies to further investigate this issue.

Association of Affected Neurocircuitry With Deficit of Response Inhibition and Delayed Gratification in Attention Deficit Hyperactivity Disorder: A Narrative Review

The neural networks that constitute corticostriatothalamocortical circuits between prefrontal cortex and subcortical structure provide a heuristic framework for bridging gaps between neurocircuitry and executive dysfunction in attention deficit hyperactivity disorder (ADHD). “Cool” and “Hot” executive functional theory and the models of dual pathway are supposed to be applied within the neuropsychology of ADHD. The theoretical model elaborated response inhibition and delayed gratification in ADHD. We aimed to review and summarize the literature about the circuits on ADHD and ADHD-related comorbidities, as well as the effects of neurocircuitry on the executive dysfunction in ADHD.

SLC6A1 gene involvement in susceptibility to attention-deficit/hyperactivity disorder: A case-control study and gene-environment interaction

Attention-deficit/hyperactivity disorder (ADHD) is an early onset childhood neurodevelopmental disorder with an estimated heritability of approximately 76%. We conducted a case-control study to explore the role of the SLC6A1 gene in ADHD. The genotypes of eight variants were determined using Sequenom MassARRAY technology. The participants in the study were 302 children with ADHD and 411 controls. ADHD symptoms were assessed using the Conners Parent Symptom Questionnaire. In our study, rs2944366 was consistently shown to be associated with the ADHD risk in the dominant model (odds ratio [OR]=0.554, 95% confidence interval [CI]=0.404-0.760), and nominally associated with Hyperactive index score (P=0.027). In addition, rs1170695 has been found to be associated with the ADHD risk in the addictive model (OR=1.457, 95%CI=1.173-1.809), while rs9990174 was associated with the Hyperactive index score (P=0.010). Intriguingly, gene-environmental interactions analysis consistently revealed the potential interactions of rs1170695 with blood lead (P_mul=0.044) to modify the ADHD risk. Expression quantitative trait loci analysis suggested that these positive single nucleotide polymorphisms (SNPs) may mediate SLC6A1 gene expression. Therefore, our results suggest that selected SLC6A1 gene variants may have a significant effect on the ADHD risk.

Daily administration of yokukansan and keishito prevents social isolation-induced behavioral abnormalities and down-regulation of phosphorylation of neuroplasticity-related signaling molecules in mice

BACKGROUND

Our previous studies demonstrated that post-weaning social isolation (ISO) in mice induces behavior abnormalities such as deficits of sociability- and attention-like behaviors. These deficits can be attenuated by methylphenidate (MPH), a drug used for attention deficit hyperactivity disorder (ADHD), suggesting that ISO mice offer a potential animal model of comorbid developmental disorder with ADHD and autism spectrum disorder symptoms. This study investigated the effects of Kampo formulae, yokukansan (YKS) and keishito (KST), on the neuropsychiatric symptoms of ISO mice to clarify the therapeutic or preventive/delaying potential of these formulae for the treatment of neurodevelopmental disorders.

METHODS

Three-to-4-week old male ICR mice were socially isolated during an experimental period and YKS and KST (1523.6 and 2031.8 mg/kg, p.o.) was administered starting from week 2 and week 0 after starting ISO for the analysis of their therapeutic and preventive/delaying potentials, respectively. Sociability, attention-related behavior and fear memory were elucidated by a 3 chamber test, a water-finding test and fear conditioning test, respectively. Moreover, the phosphorylation of neuroplasticity-related signaling molecules in mice hippocampus was analyzed using western blotting.

RESULTS

In a therapeutic procedure, YKS ameliorated ISO-induced impairments of attention-like behavior and context-dependent fear memory, but not of sociability, whereas KST had no beneficial effects in ISO mice. In experiments to analyze the preventive/delaying potentials of these treatments, both YKS and KST improved sociability, attention, and context-dependent fear memory deficits. The improvement of sociability in mice by YKS and KST was not inhibited by a dopamine D₁ receptor antagonist, suggesting that YKS and KST improved the ISO-induced sociability deficit by other mechanisms besides activation of the dopaminergic system. On the other hand, the beneficial effects of YKS and KST on attention-like behavior were inhibited by a muscarinic antagonist, suggesting that YKS and KST ameliorated ISO-induced attention-like behavior through a cholinergic mechanism. Moreover, the phosphorylated forms of CaMKII and CREB were down-regulated by ISO stress and restored by YKS and KST administration.

CONCLUSIONS

These findings suggest that YKS and KST may be useful for the improvement of neurodevelopmental disorders.

Genetic Correlates of Spirituality/Religion and Depression: A Study in Offspring and Grandchildren at High and Low Familial Risk for Depression

RATIONALE

Possible genetic correlates of spirituality and depression have been identified in community samples. We investigate some of the previously identified candidates in a sample of families at both high and low-risk for depression.

METHOD

Offspring and grandchildren of individuals at high and low-risk for depression, participating in a multi-wave thirty-year longitudinal study, were assessed for seven SNPS drawn from four single gene candidates associated with systems implicated in both depression and spirituality: Serotonin (5-HT1B and 5-HT2A), Dopamine (DRD2), Oxytocin (OT) and Monoamine Vesicular Transporter (VMAT1).

RESULTS

Dopamine (DRD2) Serotonin (5-HT1B), their Transporter (VMAT1) and Oxytocin (OXTR) were positively associated with a high level of importance of spirituality or religion (S/R) in the group at low familial risk for depression. DRD2 minor allele was associated with both lifetime major depressive disorder (MDD) and spirituality in the low-risk group for depression. No SNPs were related to S/R in the group at high familial risk for depression. OXTR was associated with lifetime MDD in the full sample.

CONCLUSION

Genes for dopamine, serotonin, their vesicular transporter, and oxytocin may be associated with S/R in people at low familial risk for depression. Genes for dopamine may be associated both with S/R and increased risk for depression in people at low-risk for depression, suggesting a common pathway or physiology to mild to moderate depression. MDD is associated with oxytocin across risk groups. In the high-risk group, phenotypic expression of S/R may be suppressed.

IMPLICATIONS

The shared association of DRD2 by S/R and depression, generally found to be inversely related, calls for further research on their common physiological pathways, and the phenotypic expression of these pathways based upon use and environment. Prevention for offspring at high familial risk for depression might include support for the development of child spirituality.

A boy with conduct disorder (CD), attention deficit hyperactivity disorder (ADHD), borderline intellectual disability, and 47,XXY syndrome in combination with a 7q11.23 duplication, 11p15.5 deletion, and 20q13.33 deletion

BACKGROUND

This is a case with multiple chromosomal aberrations which are likely etiological for the observed psychiatric phenotype consisting of attention deficit hyperactivity and conduct disorders.

CASE PRESENTATION

We report on an 11 year-old boy, admitted to the pediatric hospital for behavioral difficulties and a delayed neurodevelopmental trajectory. A cytogenetic analysis and high-resolution microarray comparative genomic hybridization (CGH) analysis was performed. The cytogenetic analysis revealed 47,XYY syndrome, while CGH analysis revealed an additional duplication and two deletions. The 7q11.23 duplication is associated with speech and language delay and behavioral symptoms, a 20q13.33 deletion is associated with autism and early onset schizophrenia and the 11p15.5 microdeletion is associated with developmental delay, autism, and epilepsy. The patient underwent a psychiatric history, physical examination, laboratory testing, and a detailed cognitive, psychiatric, and occupational therapy evaluation which are reported here in detail.

CONCLUSIONS

In the case of psychiatric patients presenting with complex genetic aberrations and additional psychosocial problems, traditional psychiatric and psychological approaches can lead to significantly improved functioning. Genetic diagnostic testing can be highly informative in the diagnostic process and may be applied to patients in psychiatry in case of complex clinical presentations.

A Preliminary Study on Investigation of Serum α-Synuclein and Tau Protein Levels in Children with Attention Deficit Hyperactivity Disorder

Neurodegenerative molecules play an important role in maintaining a supply for synaptic vesicles; and they are also likely to help regulate the dopamine release which is the primary mechanism of action in pharmacological treatments for attention deficit hyperactivity disorder (ADHD). It is suggested that there could be interactions between α-synuclein and tau in cytoskeletal disorganization and synaptic dystrophy. Therefore, we aim to determine the serum levels of neurodegenerative molecules such as α-synuclein and tau in children with ADHD. The study group consisted of 25 children, aged 6-10, diagnosed with ADHD according to DSM-IV criteria and who appeared at Dicle University, Faculty of Medicine, and Department of Child Psychiatry in Diyarbakır, Turkey. 25 children, having no psychiatric disorders and medical illnesses, were selected as healthy control group. Serum α-synuclein and tau concentrations were determined by Enzyme-Linked Immuno Sorbent Assay. The α-synuclein levels of ADHD were not significantly different than those of controls. The tau levels of ADHD were found to be statistically significantly higher than those of controls. Moreover, α-synuclein levels showed a statistically significantly positive correlation with tau levels in children with ADHD. The results of our preliminary study can suggest that ADHD might possibly share a common disease mechanism with other diseases in terms of tau pathology. Increased serum tau level may be an indication of disturbance of microtubule transportation in the brains of children with ADHD.

Prevalence and assessment of biochemical parameters of attention-deficit hyperactivity disorder children in Bangladesh

Background and Objectives:

This study aimed to evaluate some new biochemical parameters that help ensuring the early and precise diagnosis of attention-deficit hyperactivity disorder (ADHD) in blood plasma.

Design and Settings:

A prospective study conducted with patients scheduled for some new biochemical parameters that help ensuring the early and precise diagnosis of ADHD in blood plasma in a Child Development Center of the Chittagong, Bangladesh.

Materials and Methods:

The study was carried out at two levels. The first level was questionnaire on personal data and disease history while the second was on biochemical examination of the plasma ammonia and lactate status. A total of 100 children (age range 2 years 4 months to 12 years 6 months, mean age 7 years 5 months) were investigated in this study among 75 were male and 25 were female. This study was conducted in Chittagong Maa-O-Shishu General Hospital, Bangladesh.

Results:

We observed that the level of plasma ammonia and lactate were higher in ADHD children (36-60 μmol/L; P < 0.05 and 22-30 μmol/L; P < 0.05, respectively) compare to a reference value. The prevalence of ADHD is higher in male (75%) than in female (25%) with a ratio of 3:1. Consanguinity increases the risk of having ADHD in the next generation.

Conclusion:

This study concludes that there might be a correlation between ADHD and increased level of plasma ammonia and lactate level, and those might be an important parameter in the diagnosis of ADHD patients.

Child maltreatment, impulsivity, and antisocial behavior in African American children: Moderation effects from a cumulative dopaminergic gene index

A model examining the effects of an increasing number of maltreatment subtypes experienced on antisocial behavior, as mediated by impulsivity and moderated by a polygenic index of dopaminergic genotypes, was investigated. An African American sample of children (N = 1,012, M age = 10.07) with and without maltreatment histories participated. Indicators of aggression, delinquency, and disruptive peer behavior were obtained from peer- and counselor-rated measures to form a latent variable of antisocial behavior; impulsivity was assessed by counselor report. Five genotypes in four dopaminergic genes (dopamine receptors D4, D2, known as DRD4, DRD2; dopamine active transporter 1, known as DAT1; and catechol-O-methyltransferase, known as COMT) conferring heightened environmental sensitivity were combined into one polygenic index. Using structural equation modeling, a first-stage, moderated-mediation model was evaluated. Age and sex were entered as covariates, both as main effects and in interaction with maltreatment and the gene index. The model had excellent fit: χ2 (32, N = 1,012) = 86.51, p < .001; comparative fit index = 0.982, Tucker-Lewis index = 0.977, root mean square error of approximation = 0.041, and standardized root mean square residual = 0.022. The effect of maltreatment subtypes on antisocial behavior was partially mediated by impulsivity (β = 0.173, p < .001), and these relations were moderated by the number of differentiating dopaminergic genotypes. Specifically, a significant Gene × Environment interaction (β = 0.016, p = .013) indicated that the relation between maltreatment and impulsivity was stronger as children evinced more differentiating genotypes, thereby strengthening the mediational effect of impulsivity on antisocial behavior. These findings elucidate the manner by which maltreated children develop early signs of antisocial behavior, and the genetic mechanisms involved in greater vulnerability for maladaptation in impulse control within the context of child maltreatment.

Developmentally Sensitive Interaction Effects of Genes and the Social Environment on Total and Subcortical Brain Volumes

Smaller total brain and subcortical volumes have been linked to psychopathology including attention-deficit/hyperactivity disorder (ADHD). Identifying mechanisms underlying these alterations, therefore, is of great importance. We investigated the role of gene-environment interactions (GxE) in interindividual variability of total gray matter (GM), caudate, and putamen volumes. Brain volumes were derived from structural magnetic resonance imaging scans in participants with (N = 312) and without ADHD (N = 437) from N = 402 families (age M = 17.00, SD = 3.60). GxE effects between DAT1, 5-HTT, and DRD4 and social environments (maternal expressed warmth and criticism; positive and deviant peer affiliation) as well as the possible moderating effect of age were examined using linear mixed modeling. We also tested whether findings depended on ADHD severity. Deviant peer affiliation was associated with lower caudate volume. Participants with low deviant peer affiliations had larger total GM volumes with increasing age. Likewise, developmentally sensitive GxE effects were found on total GM and putamen volume. For total GM, differential age effects were found for DAT1 9-repeat and HTTLPR L/L genotypes, depending on the amount of positive peer affiliation. For putamen volume, DRD4 7-repeat carriers and DAT1 10/10 homozygotes showed opposite age relations depending on positive peer affiliation and maternal criticism, respectively. All results were independent of ADHD severity. The presence of differential age-dependent GxE effects might explain the diverse and sometimes opposing results of environmental and genetic effects on brain volumes observed so far.

Disorder-specific genetic factors in obsessive-compulsive disorder: A comprehensive meta-analysis

Much remains to be learned about the etiology of obsessive-compulsive disorder (OCD). Twin studies suggest that it arises from both disorder-specific and non-specific genetic factors. To understand the etiology of OCD per se, it is necessary to identify disorder-specific factors. Previous research shows that OCD is associated with serotonin-related polymorphisms (5-HTTLPR coded as triallelic and HTR2A rs6311/rs6313) and, in males, a polymorphism involved in catecholamine modulation; COMT (rs4680). The present study is the first comprehensive meta-analysis to investigate whether these polymorphisms are specific to OCD. A meta-analysis was conducted for genetic association studies of OCD or any other psychiatric disorder, published in any language, in any country. A total of 551 studies were examined, of which 290 were included, consisting of 47,358 cases and 68,942 controls from case control studies, and 2,443 trios from family based studies. The main meta-analysis was limited to those disorders in which there were at least five datasets (studies or sub-studies) per disorder. Results confirmed that OCD is associated with polymorphisms of 5-HTTLPR, HTR2A, and, in males only, COMT. These polymorphisms were not associated with almost all other forms of psychopathology, including unipolar mood disorders, bipolar disorder, panic disorder, schizophrenia, and alcohol dependence. OCD, compared to most other disorders, had a significantly stronger association with particular alleles of each of the polymorphisms. Results did not differ across ancestral groups (Asian vs. Caucasian), designs (case control vs. family based), or diagnostic systems. Results suggest that the polymorphisms investigated in this study are relatively specific to OCD.

Dopamine's Actions in Primate Prefrontal Cortex: Challenges for Treating Cognitive Disorders

The prefrontal cortex (PFC) elaborates and differentiates in primates, and there is a corresponding elaboration in cortical dopamine (DA). DA cells that fire to both aversive and rewarding stimuli likely project to the dorsolateral PFC (dlPFC), signaling a salient event. Since 1979, we have known that DA has an essential influence on dlPFC working memory functions. DA has differing effects via D1 (D1R) versus D2 receptor (D2R) families. D1R are concentrated on dendritic spines, and D1/5R stimulation produces an inverted U-shaped dose response on visuospatial working memory performance and Delay cell firing, the neurons that generate representations of visual space. Optimal levels of D1R stimulation gate out "noise," whereas higher levels, e.g., during stress, suppress Delay cell firing. These effects likely involve hyperpolarization-activated cyclic nucleotide-gated channel opening, activation of GABA interneurons, and reduced glutamate release. Dysregulation of D1R has been related to cognitive deficits in schizophrenia, and there is a need for new, lower-affinity D1R agonists that may better mimic endogenous DA to enhance mental representations and improve cognition. In contrast to D1R, D2R are primarily localized on layer V pyramidal cell dendrites, and D2/3R stimulation speeds and magnifies the firing of Response cells, including Response Feedback cells. Altered firing of Feedback neurons may relate to positive symptoms in schizophrenia. Emerging research suggests that DA may have similar effects in the ventrolateral PFC and frontal eye fields. Research on the orbital PFC in monkeys is just beginning and could be a key area for future discoveries.

Doping the Mind: Dopaminergic Modulation of Prefrontal Cortical Cognition

The prefrontal cortex is the center of cognitive control. Processing in prefrontal cortical circuits enables us to direct attention to behaviorally relevant events; to memorize, structure, and categorize information; and to learn new concepts. The prefrontal cortex receives strong projections from midbrain neurons that use dopamine as a transmitter. In this article, we review the crucial role dopamine plays as a modulator of prefrontal cognitive functions, in the primate brain in particular. Following a summary of the anatomy and physiology of the midbrain dopamine system, we focus on recent studies that investigated dopaminergic effects in prefrontal cortex at the cellular level. We then discuss how unregulated prefrontal dopamine signaling could contribute to major disorders of cognition. The studies highlighted in this review demonstrate the powerful influence dopamine exerts on the mind.

A Population-Based Imaging Genetics Study of Inattention/Hyperactivity: Basal Ganglia and Genetic Pathways

OBJECTIVE

Although attention-deficit/hyperactivity disorder (ADHD) is 1 of the most common neurodevelopmental disorders, little is known about the neurobiology. Clinical studies suggest basal ganglia morphology plays a role. Furthermore, hyperactivity/impulsivity symptoms have recently been linked to genetic pathways involved in dopamine/norepinephrine and serotonin neurotransmission and neuritic outgrowth. We aimed to assess the association between ADHD symptoms, basal ganglia volume, and the 3 proposed genetic pathways in a pediatric population-based sample. With this, we aimed to investigate the generalizability of earlier clinical findings to the general population.

METHOD

This study included a population-based sample of 1,871 children with data on ADHD symptoms and genetic data, and 344 children with additional neuroimaging data. Regression analyses between ADHD symptom severity and volumetric data of the basal ganglia were performed. Also, gene-set analyses investigating the association between both ADHD symptom severity and basal ganglia volume with the dopamine/norepinephrine, serotonin, and neuritic outgrowth pathways were performed.

RESULTS

More inattention and hyperactivity/impulsivity symptoms were associated with a smaller volume of the putamen (β = -0.13, p = .034), which was regarded as trend-level after correction for multiple testing. Stratified analyses showed a stronger putamen-hyperactivity association in children with clinical scores, although a similar trend was visible in the nonclinical subsample. The genetic pathways were not related to either ADHD symptoms or basal ganglia volume.

CONCLUSION

ADHD symptoms were marginally related to putamen volume in our population-based sample. We found no evidence for a role of dopamine/norepinephrine, serotonin, or neuritic outgrowth genetic pathways in ADHD symptom severity.

Association of SNAP-25, SLC6A2, and LPHN3 with OROS methylphenidate treatment response in attention-deficit/hyperactivity disorder

OBJECTIVES

Our study aimed to identify the association of norepinephrine transporter gene (SLC6A2), synaptosomal-associated protein of the 25-kDa gene (SNAP-25), and latrophilin 3 gene (LPHN3) with osmotic-controlled release oral delivery system methylphenidate (OROS MPH) treatment response.

METHODS

One hundred thirty-nine children and adolescents with attention-deficit/hyperactivity disorder (ADHD) were recruited. We selected rs192303, rs3785143 in SLC6A2; rs3746544 (1065 T>G) in SNAP-25; and rs6551665, rs1947274, and rs2345039 in LPHN3 to examine the association of OROS MPH treatment response with each single nucleotide polymorphism. We first defined good response group when the Korean version of the ADHD rating scale score at 8 weeks was decreased for more than 50% of baseline scores and compared genotype frequencies in good response group with poor group. Second, we defined it when the Clinical Global Impression-Improvement score at 8 weeks was 1 or 2, and we also analyzed the genotype frequencies.

RESULTS

There was a significant association between the 1065 T>G of SNAP-25 gene and OROS MPH response, with the good response group defined by the Korean version of ADHD rating scale scores; 33.3% of the subjects with GG genotype showed a good response, whereas 74.7% of those with TT genotype and 72.5% of those with TG genotype showed good responses (P=0.034). SLC6A2 rs192303 was related with OROS MPH treatment response when we defined good treatment response by Clinical Global Impression-Improvement (P=0.009).

CONCLUSIONS

Our study suggested that SNAP-25 gene and SLC6A2 were involved with OROS MPH response.

Differential susceptibility to maternal expressed emotion in children with ADHD and their siblings? Investigating plasticity genes, prosocial and antisocial behaviour

The differential susceptibility theory states that children differ in their susceptibility towards environmental experiences, partially due to plasticity genes. Individuals carrying specific variants in such genes will be more disadvantaged in negative but, conversely, more advantaged in positive environments. Understanding gene-environment interactions may help unravel the causal mechanisms involved in multifactorial psychiatric disorders such as Attention-Deficit/Hyperactivity Disorder (ADHD). The differential susceptibility theory was examined by investigating the presence of interaction effects between maternal expressed emotion (EE; warmth and criticism) and the solitary and combined effects of plasticity genes (DAT1, DRD4, 5-HTT) on prosocial and antisocial behaviour (measured with parent- and self-reports) in children with ADHD and their siblings (N = 366, M = 17.11 years, 74.9% male). Maternal warmth was positively associated with prosocial behaviour and negatively with antisocial behaviour, while maternal criticism was positively associated with antisocial behaviour and negatively with prosocial behaviour. No evidence of differential susceptibility was found. The current study found no evidence for differential susceptibility based on the selected plasticity genes, in spite of strong EE-behaviour associations. It is likely that additional factors play a role in the complex relationship between genes, environment and behaviour.

Functional and structural specific roles of activity-driven BDNF within circuits formed by single spiny stellate neurons of the barrel cortex

Brain derived neurotrophic factor (BDNF) plays key roles in several neurodevelopmental disorders and actions of pharmacological treatments. However, it is unclear how specific BDNF’s effects are on different circuit components. Current studies have largely focused on the role of BDNF in modification of synaptic development. The precise roles of BDNF in the refinement of a functional circuit in vivo remain unclear. Val66Met polymorphism of BDNF may be associated with increased risk for cognitive impairments and is mediated at least in part by activity-dependent trafficking and/or secretion of BDNF. Using mutant mice that lacked activity-driven BDNF expression (bdnf-KIV), we previously reported that experience regulation of the cortical GABAergic network is mediated by activity-driven BDNF expression. Here, we demonstrate that activity-driven BDNF’s effects on circuits formed by the layer IV spiny stellate cells are highly specific. Structurally, dendritic but not axonal morphology was altered in the mutant. Physiologically, GABAergic but not glutamatergic synapses were severely affected. The effects on GABA transmission occurs via presynaptic alteration of calcium-dependent release probability. These results suggest that neuronal activity through activity-driven BDNF expression, can selectively regulate specific features of layer IV circuits in vivo. We postulate that the role of activity-dependent BDNF is to modulate the computational ability of circuits that relate to the gain control (i.e., feed-forward inhibition); whereas the basic wiring of circuits relevant to the sensory pathway is spared. Gain control modulation within cortical circuits has broad impact on cognitive processing and brain state-transitions. Cognitive behavior and mode is determined by brain states, thus the studying of circuit alteration by endogenous BDNF provides insights into the cellular and molecular mechanisms of diseases mediated by BDNF.

Short-term oral atrazine exposure alters the plasma metabolome of male C57BL/6 mice and disrupts α-linolenate, tryptophan, tyrosine and other major metabolic pathways

Overexposure to the commonly used herbicide atrazine (ATR) affects several organ systems, including the brain. Previously, we demonstrated that short-term oral ATR exposure causes behavioral deficits and dopaminergic and serotonergic dysfunction in the brains of mice. Using adult male C57BL/6 mice, the present study aimed to investigate effects of a 10-day oral ATR exposure (0, 5, 25, 125, or 250mg/kg) on the mouse plasma metabolome and to determine metabolic pathways affected by ATR that may be reflective of ATR's effects on the brain and useful to identify peripheral biomarkers of neurotoxicity. Four hours after the last dosing on day 10, plasma was collected and analyzed with high-performance, dual chromatography-Fourier-transform mass spectrometry that was followed by biostatistical and bioinformatic analyses. ATR exposure (≥5mg/kg) significantly altered plasma metabolite profile and resulted in a dose-dependent increase in the number of metabolites with ion intensities significantly different from the control group. Pathway analyses revealed that ATR exposure strongly correlated with and disrupted multiple metabolic pathways. Tyrosine, tryptophan, linoleic acid and α-linolenic acid metabolic pathways were among the affected pathways, with α-linolenic acid metabolism being affected to the greatest extent. Observed effects of ATR on plasma tyrosine and tryptophan metabolism may be reflective of the previously reported perturbations of brain dopamine and serotonin homeostasis, respectively. ATR-caused alterations in the plasma profile of α-linolenic acid metabolism are a potential novel and sensitive plasma biomarker of ATR effect and plasma metabolomics could be used to better assess the risks, including to the brain, associated with ATR overexposure.

Biomarkers in the diagnosis of ADHD--promising directions

The etiology and pathogenesis of attention-deficit/hyperactivity disorder (ADHD) are unclear and a more valid diagnosis would certainly be welcomed. Starting from the literature, we built an hypothetical pyramid representing a putative set of biomarkers where, at the top, variants in DAT1 and DRD4 genes are the best candidates for their associations to neuropsychological tasks, activation in specific brain areas, methylphenidate response and gene expression levels. Interesting data come from the noradrenergic system (norepinephrine transporter, norepinephrine, 3-methoxy-4-hydroxyphenylglycol, monoamine oxidase, neuropeptide Y) for their altered peripheral levels, their association with neuropsychological tasks, symptomatology, drugs effect and brain function. Other minor putative genetic biomarkers could be dopamine beta hydroxylase and catechol-O-methyltransferase. In the bottom, we placed endophenotype biomarkers. A more deep integration of "omics" sciences along with more accurate clinical profiles and new high-throughput computational methods will allow us to identify a better list of biomarkers useful for diagnosis and therapies.

Methylphenidate ameliorates depressive comorbidity in ADHD children without any modification on differences in serum melatonin concentration between ADHD subtypes

The vast majority of Attention-deficit/hyperactivity disorder (ADHD) patients have other associated pathologies, with depressive symptoms as one of the most prevalent. Among the mediators that may participate in ADHD, melatonin is thought to regulate circadian rhythms, neurological function and stress response. To determine (1) the serum baseline daily variations and nocturnal excretion of melatonin in ADHD subtypes and (2) the effect of chronic administration of methylphenidate, as well as the effects on symptomatology, 136 children with ADHD (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision: DSM-IV-TR criteria) were divided into subgroups using the “Children’s Depression Inventory” (CDI). Blood samples were drawn at 20:00 and 09:00 h, and urine was collected between 21:00 and 09:00 h, at inclusion and after 4.61 ± 2.29 months of treatment. Melatonin and its urine metabolite were measured by radioimmunoassay RIA. Factorial analysis was performed using STATA 12.0. Melatonin was higher predominantly in hyperactive-impulsive/conduct disordered children (PHI/CD) of the ADHD subtype, without the influence of comorbid depressive symptoms. Methylphenidate ameliorated this comorbidity without induction of any changes in the serum melatonin profile, but treatment with it was associated with a decrease in 6-s-melatonin excretion in both ADHD subtypes. Conclusions: In untreated children, partial homeostatic restoration of disrupted neuroendocrine equilibrium most likely led to an increased serum melatonin in PHI/CD children. A differential cerebral melatonin metabolization after methylphenidate may underlie some of the clinical benefit.

Maternal unresponsiveness and child disruptive problems: the interplay of uninhibited temperament and dopamine transporter genes

This study examined how and why dopamine transporter (DAT1) susceptibility alleles moderate the relation between maternal unresponsiveness and young children's behavior problems in a disadvantaged, predominantly minority sample of 201 two-year-old children and their mothers. Using a multimethod, multisource design, the findings indicated that a genetic composite of DAT1 susceptibility alleles (rs27072, rs40184) potentiated associations between maternal unresponsive caregiving and increases in children's behavior problems 2 years later. Moderator-mediated-moderation analyses further revealed that the DAT1 diathesis was more proximally mediated by the potentiating effects of children's uninhibited temperament in the pathway between maternal unresponsiveness and disruptive behavior problems. Results are interpreted in the context of supporting and advancing the biosocial developmental model (Beauchaine & Gatzke-Kopp, 2012).

Sex-specific association of brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and plasma BDNF with attention-deficit/hyperactivity disorder in a drug-naïve Han Chinese sample

A functional polymorphism of the brain derived neurotrophic factor gene (BDNF) (Val66Met) has been suggested to be involved in the pathogenesis of attention-deficit/hyperactivity disorder (ADHD). It also has an impact on peripheral BDNF levels in psychiatric disorders. This study examined the association of Val66Met with plasma BDNF level of ADHD in Han Chinese children (170 medication - naïve ADHD patients and 155 unaffected controls, aged 6-16 years). The Val allele was showed a higher frequency in females with ADHD (n=84) than controls (P=0.029) from the case-control association study. The analysis of covariance (ANCOVA) indicated that the mean plasma BDNF levels of ADHD patients were significantly higher than that of controls (P=0.001). We performed both total sample and sex stratified analyses to investigate the effect of Val66Met genotype on the plasma BDNF levels, but only a trend of association was found in females with ADHD (n=84), with a tendency of lower plasma BDNF level in Val allele carriers than Met/Met genotype carriers (P=0.071). Our results suggested a sex-specific association between BDNF and ADHD. Furthermore, there was a possible sex-specific relationship between the BDNF Val66Met genotype and plasma BDNF levels. However, further studies are required to elucidate the role of BDNF in ADHD.

Does adult ADHD interact with COMT val (158) met genotype to influence working memory performance?

Both attention-deficit/hyperactivity disorder (ADHD) and catechol-O-methyltransferase (COMT) genotype have been linked to altered dopaminergic transmission and possible impairment in frontal lobe functioning. This study offers an investigation of a possible interaction between ADHD diagnosis and COMT genotype on measures of working memory and executive function. Thirty-five adults with ADHD, who were recruited from the ADHD outpatient clinic at the Department of Psychiatry, Psychosomatics and Psychotherapy, University of Würzburg, and thirty-five matched healthy controls completed the Digit Span test and the Stroop Color Word Test. While there were no main effects of ADHD or COMT, the two factors interacted on both Digit Span subtests with the two groups' met/met carriers showing significantly different performance on the Digit Span Forward subtest and the val/val carriers showing significantly different performance on the Digit Span Backward subtest. Findings provide preliminary support for a differential impact of COMT genotype on working memory measures in adult patients with ADHD compared to healthy controls.

The Roots of Autism and ADHD Twin Study in Sweden (RATSS)

Neurodevelopmental disorders affect a substantial minority of the general population. Their origins are still largely unknown, but a complex interplay of genetic and environmental factors causing disturbances of the central nervous system's maturation and a variety of higher cognitive skills is presumed. Only limited research of rather small sample size and narrow scope has been conducted in neurodevelopmental disorders using a twin-differences design. The Roots of Autism and ADHD Twin Study in Sweden (RATSS) is an ongoing project targeting monozygotic twins discordant for categorical or dimensional autistic and inattentive/hyperactive-impulsive phenotypes as well as other neurodevelopmental disorders, and typically developing twin controls. Included pairs are 9 years of age or older, and comprehensively assessed for psychopathology, medical history, neuropsychology, and dysmorphology, as well as structural, functional, and molecular brain imaging. Specimens are collected for induced pluripotent (iPS) and neuroepithelial stem cells, genetic, gut bacteria, protein-/monoamine, and electron microscopy analyses. RATSS's objective is to generate a launch pad for novel surveys to understand the complexity of genotype-environment-phenotype interactions in autism spectrum disorder and attention-deficit hyperactivity disorder (ADHD). By October 2013, RATSS had collected data from 55 twin pairs, among them 10 monozygotic pairs discordant for autism spectrum disorder, seven for ADHD, and four for other neurodevelopmental disorders. This article describes the design, recruitment, data collection, measures, collected pairs' characteristics, as well as ongoing and planned analyses in RATSS. Potential gains of the study comprise the identification of environmentally mediated biomarkers, the emergence of candidates for drug development, translational modeling, and new leads for prevention of incapacitating outcomes.

Sons and daughters beyond your control: episodes in the prehistory of the attention deficit/hyperactivity syndrome

Hyperactive and inattentive children have been discussed in both the pedagogic and medical literature since the nineteenth century, and many controversies associated with attention deficit and hyperactivity disorder (ADHD) have been repeatedly analyzed in different contexts. The 'prehistory' of the ADHD concept-that is, up to the definition of ADHD in DSM-III and of the corresponding 'hyperkinetic disorder' in ICD-9-is outlined, with an emphasis on the literature not previously discussed in English language reviews of the subject.

Genome-wide copy number variation analysis in adult attention-deficit and hyperactivity disorder

Attention-deficit and hyperactivity disorder (ADHD) is a common psychiatric disorder with a worldwide prevalence of 5-6% in children and 4.4% in adults. Recently, copy number variations (CNVs) have been implicated in different neurodevelopmental disorders such as ADHD. Based on these previous reports that focused on pediatric cohorts, we hypothesize that structural variants may also contribute to adult ADHD and that such genomic variation may be enriched for CNVs previously identified in children with ADHD. To address this issue, we performed for the first time a whole-genome CNV study on 400 adults with ADHD and 526 screened controls. In agreement with recent reports in children with ADHD or in other psychiatric disorders, we identified a significant excess of insertions in ADHD patients compared to controls. The overall rate of CNVs >100 kb was 1.33 times higher in ADHD subjects than in controls (p = 2.4e-03), an observation mainly driven by a higher proportion of small events (from 100 kb to 500 kb; 1.35-fold; p = 1.3e-03). These differences remained significant when we considered CNVs that overlap genes or when structural variants spanning candidate genes for psychiatric disorders were evaluated, with duplications showing the greatest difference (1.41-fold, p = 0.024 and 2.85-fold, p = 8.5e-03, respectively). However, no significant enrichment was detected in our ADHD cohort for childhood ADHD-associated CNVs, CNVs previously identified in at least one ADHD patient or CNVs previously implicated in autism or schizophrenia. In conclusion, our study provides tentative evidence for a higher rate of CNVs in adults with ADHD compared to controls and contributes to the growing list of structural variants potentially involved in the etiology of the disease.

Sequence analysis of the ADRA2A coding region in children affected by attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a common neurobehavioral pathology characterized by distinct degrees of inattention, hyperactivity and impulsivity. Although ADHD etiology remains elusive, the ADRA2A candidate gene underlies a particular interest, since it participates in the prefrontal cortex regulation of executive function. Three SNPs located on 5' and 3'UTR regions of the gene have been extensively explored but none of them have been definitely validated as a predisposition or a causative sequence variation. In this study, in order to determine whether ADRA2A non-synonymous sequence variants, resulting in biochemical modifications of the protein, are a common cause of the disease we sequenced the complete ADRA2A coding region in a panel of ADHD children of Colombian origin. We identified the c.1138 C>A (p.Arg380Arg) silent substitution. We conclude that ADRA2A non-synonymous sequence variants do not cause ADHD in our sample population. We cannot formerly discard a potential role of this gene during ADHD pathogenesis since only the coding region was analysed. We hope that these results will encourage further researchers to sequence the promoter and coding regions of ADRA2A in large panels of ADHD patients from distinct ethnical origins.