An exploratory study of ADHD among second-degree relatives of ADHD children

The Synaptic and Circuit Functions of Vitamin D in Neurodevelopment Disorders

Vitamin D deficiency/insufficiency is a public health issue around the world. According to epidemiological studies, low vitamin D levels have been associated with an increased risk of some neurodevelopmental disorders, including autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). Animal models reveal that vitamin D has a variety of impacts on the synapses and circuits in the brain. A lack of vitamin D affects the expression of synaptic proteins, as well as the synthesis and metabolism of various neurotransmitters. Depending on where vitamin D receptors (VDRs) are expressed, vitamin D may also regulate certain neuronal circuits through the endocannabinoid signaling, mTOR pathway and oxytocin signaling. While inconsistently, some data suggest that vitamin D supplementation may be able to reduce the core symptoms of ASD and ADHD. This review emphasizes vitamin D's role in the synaptic and circuit mechanisms of neurodevelopmental disorders including ASD and ADHD. Future application of vitamin D in these disorders will depend on both basic research and clinical studies, in order to make the transition from the bench to the bedside.

Comorbidity and patterns of familial aggregation in attention-deficit/hyperactivity disorder and bipolar disorder in a family study of affective and anxiety spectrum disorders

The aim of this study is to examine the familial aggregation of Attention-deficit/hyperactivity disorder (ADHD) and its cross-transmission with bipolar disorder (BD) in a community-based family study of mood spectrum disorders. A clinically-enriched community sample of 562 probands recruited from the greater Washington, DC metropolitan area and their 698 directly interviewed relatives were included in analyses. Inclusion criteria were English speaking and consent to contact at least two first-degree relatives. Standard family study methodology was used and DSM-IV classified mental disorders were ascertained through a best-estimate procedure based on direct semi-structured interviews and multiple family history reports. There was specificity of familial aggregation of both bipolar I disorder (BD I) and bipolar II disorder (BD II) (i.e., BD I OR = 6.08 [1.66, 22.3]; BD II OR = 2.98 [1.11, 7.96]) and ADHD (ADHD OR = 2.13 [1.16, 3.95]). However, there was no evidence for cross-transmission of BD and ADHD in first degree relatives (i.e., did not observe increased rates of BD in relatives of those with ADHD and vice versa; all ps > 0.05). The specificity of familial aggregation of ADHD and BD alongside the absence of shared familial risk are consistent with the notion that the comorbidity between ADHD and BD may be attributable to diagnostic artifact, could represent a distinct BD suptype characterized by childhood-onset symptoms, or the possibility that attention problems serve as a precursor or consequence of BD.

Effect of vitamin D treatment in children with attention-deficit hyperactivity disorder

BACKGROUND

In this research the symptom improvement of attention-deficit hyperactivity disorder (ADHD) of children was assessed by oral vitamin D administration in Tabriz, Iran.

METHODS

In this double-blind, randomized clinical trials, 96 children (2-18 years) were enrolled to placebo and vitamin D groups. Children took vitamin D pearl (50,000 IU/week) or placebo for 6 weeks. Children, who had the change in methylphenidate dosage and received any anticonvulsants and corticosteroids were excluded from the research. ADHD symptoms were diagnosed by Conners parent rating scale (CPRS) test at baseline and after intervention. ADHD Conners divided into inattention (IA), hyperactivity/impulsivity (H/I) and combination type (C) subscales. Vitamin D serum level was assessed at baseline and after 8 weeks in both groups.

RESULTS

The differences between CPRS and its subscales were not significant at baseline (P > 0.05). The Conners IA score was decreased in vitamin D group (P < 0.05; adjusted with age and baseline values). ADHD Conners and all subscale scores reduced remarkably after intervention in patients with insufficient level of vitamin D compared to placebo (P < 0.05).

CONCLUSIONS

Oral vitamin D improved ADHD symptoms with a particular effect on inattention symptoms. In addition, symptoms related to all subscales were improved remarkably in patients with insufficient level of vitamin D. Vitamin D treatment in children with ADHD could be considered due to the expand benefit of vitamin D in body.

Predicting attention deficit hyperactivity disorder using pregnancy and birth characteristics

PURPOSE

The aim of this study was to evaluate maternal, prenatal, perinatal, and postpartum parameters as risk factors for the later development of an attention deficit hyperactivity disorder (ADHD) in the child.

METHODS

Women who had given birth at Erlangen University Hospital between 1996 and 1999 were sent a questionnaire in 2009. The results of the questionnaire were correlated with the prospectively collected data for the births in 1996-1999.

RESULTS

A total of 573 mother and child pairs were analyzed. Forty-four of the mothers reported that their child had ADHD (7.7%). No significant associations were found for the following parameters: mother's age; mother's educational level; number of the pregnancy; maternal weight before and at the end of pregnancy; mother's height; alcohol consumption during pregnancy; mode of delivery; gestational week; birthweight; umbilical artery blood values; Apgar score at 5 and 10 min; or breastfeeding. The parameters of smoking in pregnancy and an Apgar score lower than 7 after 1 min were significantly associated with a risk for later development of ADHD.

CONCLUSIONS

This analysis of maternal, prenatal, perinatal, and postnatal parameters found that smoking in pregnancy and a low Apgar score 1 min after birth are associated with a significantly greater risk for the development of ADHD. Beyond the question of the causal mechanism involved, this is a relevant finding, since smoking during pregnancy is a preventable risk factor.

Vitamin D status in children with attention-deficit-hyperactivity disorder

BACKGROUND

Attention-deficit-hyperactivity disorder (ADHD), one of the most common psychiatric disorders of childhood, has an early onset, affecting 2-18% of children worldwide. The etiopathogenesis of ADHD is obscure. In recent studies, a low level of vitamin D has been found in association with many disorders as well as in neuropsychiatric diseases. The aim of this study was therefore to investigate serum vitamin D level in pediatric ADHD patients.

METHODS

A total of 60 ADHD patients and 30 healthy controls were included in the study. The age of both groups was in the 7-18-year-old range. Serum 25-OH-vitamin D, calcium, phosphorus and alkaline phosphatase were investigated.

RESULTS

Serum 25-OH-vitamin D was found to be significantly lower in children and adolescents with ADHD compared to healthy controls, and no significant differences were found between the groups in terms of other variables. 25-OH-vitamin D level in the ADHD group and control group was, respectively, 20.9 ± 19.4 ng/mL and 34.9 ± 15.4 ng/mL (P = 0.001).

CONCLUSION

There is an association between lower 25-OH-vitamin D concentration and ADHD in childhood and adolescence. To the authors' knowledge this is the first study to investigate the relationship between vitamin D and ADHD in children.

Attention deficit hyperactivity disorder

Over the last two decades, there have been numerous technical and methodological advances available to clinicians and researchers to better understand attention deficit hyperactivity disorder (ADHD) and its etiology. Despite the growing body of literature investigating the disorder's pathophysiology, ADHD remains a complex psychiatric disorder to characterize. This chapter will briefly review the literature on ADHD, with a focus on its history, the current genetic insights, neurophysiologic theories, and the use of neuroimaging to further understand the etiology. We address some of the major concerns that remain unclear about ADHD, including subtype instability, heterogeneity, and the underlying neural correlates that define the disorder. We highlight that the field of ADHD is rapidly evolving; the descriptions provided here will hopefully provide a sturdy foundation for which to build and improve our understanding of the disorder.

The longitudinal course of attention deficit/hyperactivity disorder in velo-cardio-facial syndrome

OBJECTIVE

To evaluate predictors of persistence of attention deficit/hyperactivity disorder (ADHD) in a large sample of children with velo-cardio-facial syndrome (VCFS) with and without ADHD followed prospectively into adolescence.

STUDY DESIGN

Children with VCFS with (n = 37) and without (n = 35) ADHD who were on average 11 years old at the baseline assessment and 15 years old at the follow-up assessment were comprehensively assessed with structured diagnostic interviews and assessments of behavioral, cognitive, social, school, and family functioning. Control participants both with and without ADHD were also followed prospectively.

RESULTS

In adolescence, 65% of children with VCFS continued to have findings consistent with ADHD. Childhood predictors of persistence were higher rates of familial ADHD, having childhood depression, having higher levels of hyperactivity, and a larger number of intrusion errors on a verbal list learning test at baseline. Approximately 15% of children with VCFS who did not have ADHD at Time 1 met diagnostic criteria for ADHD at Time 2. All of these children had subthreshold ADHD symptoms at Time 1.

CONCLUSIONS

These findings prospectively confirm that persistence of ADHD into adolescence in VCFS is predicted by childhood variables that have been previously documented in the non-VCFS ADHD literature.

Attention-deficit/hyperactivity disorder genomics: update for clinicians

Attention deficit, hyperactivity disorder (ADHD) is familial and highly heritable. Several candidate genes involved in neurotransmission have been identified, however these confer minimal risk, suggesting that for the most part, ADHD is not caused by single common genetic variants. Advances in genotyping enabling investigation at the level of the genome have led to the discovery of rare structural variants suggesting that ADHD is a genomic disorder, with potentially thousands of variants, and common neuronal pathways disrupted by numerous rare variants resulting in similar ADHD phenotypes. Heritability studies in humans also indicate the importance of epigenetic factors, and animal studies are deciphering some of the processes that confer risk during gestation and throughout the post-natal period. These and future discoveries will lead to improved diagnosis, individualized treatment, cures, and prevention. These advances also highlight ethical and legal issues requiring management and interpretation of genetic data and ensuring privacy and protection from misuse.

The behavioural profile of children with attention-deficit/ hyperactivity disorder and of their siblings

The behavioural profiles in N = 69 index children with attention-deficit/hyperactivity disorder (ADHD),N = 32 siblings with ADHD, N = 35 siblings without ADHD, and N = 36 normal controls were compared by the use of standardized parent and teacher rating scales. The four groups were matched by age and IQ. The behavioural profiles of the two ADHD groups were very similar not only in the behavioural domains of ADHD, but also in scales measuring emotional and conduct problems. Siblings without ADHD shared more similarities with normal controls except for more emotional problems. These general trends were stronger in the parent compared to the teacher ratings. These findings indicate that not only ADHD-related but also other behaviours show a strong family aggregation. The informant differences may reflect context dependent differences in child behaviour and contrast effects particularly in parental ratings.

Parents' reactions to youths' hyperactivity, impulsivity, and attention problems

Hyperactivity, impulsivity, and attention problems (HIA) in children and adolescents are stressful for parents. In this study, we used theories of parents' perceived power and attributions for youths' behaviors to develop a model to understand parents' reactions to their youths' HIA. We followed 706 youths (376 boys and 330 girls, aged 10-12 years at T1) and their parents in a community-based project over 5 years. Measures of youths' HIA, youths' unresponsiveness to correction, parents' feelings of powerlessness, parental monitoring, and parents' negative behaviors toward their youths, were used. HIA in youths predicted increases in parents' perceptions that their youths were unresponsive to correction, which in turn prompted parents to feel more powerless over time. Further, parents' feelings of powerlessness were associated with increases in negative parenting behaviors over time. These results indicate a movement to more negative parenting practices over time as a result of youths' HIA.

Parental ADHD status and its association with proband ADHD subtype and severity

OBJECTIVE

To better understand the familial transmission of attention deficit hyperactivity disorder (ADHD), a highly heritable disorder, the effects of paternal and maternal ADHD status on probands' ADHD symptoms and subtypes were investigated.

STUDY DESIGN

In 323 trios with ADHD, data from a structured interview and a self-report scale (score of >21) were used to determine ADHD probands' diagnostic status and parental ADHD status, respectively. Parental ADHD status on proband ADHD severity and subtypes was investigated.

RESULTS

ADHD criteria were endorsed by 23% of fathers and 27% of mothers, and by at least one parent in 41% of the cases. ADHD severity was higher for children whose parents had ADHD versus those whose parents were without it. Paternal ADHD was associated with an increased likelihood of ADHD combined subtype (odds ratio = 3.56) and a decreased likelihood of the inattentive subtype (odds ratio = 0.34) in male children.

CONCLUSIONS

Parental ADHD status appears to confer different risks for the severity of hyperactive-impulsive and inattentive symptoms depending on parental sex; however, parental ADHD self-report scale score has low to negligible correlation with proband's ADHD severity. Biparental ADHD does not appear to have an additive or synergistic effect on the proband's ADHD severity.

Family-based association analysis of a statistically derived quantitative traits for ADHD reveal an association in DRD4 with inattentive symptoms in ADHD individuals

The objective of this study was to determine whether single nucleotide polymorphisms (SNPs) within candidate genes for ADHD are associated with quantitative phenotypes generated from inattentive and hyperactive-impulsive symptoms. One hundred forty-three SNPs were genotyped in and around five ADHD candidate genes. A highly heritable quantitative phenotype was generated at each SNP by weighting inattentive and hyperactive-impulsive symptoms. Once these phenotypes were generated, a screening procedure was used to select and test the five SNP/phenotype combinations with the greatest power to detect an association for each candidate gene. Adjacent SNPs in the promoter region of DRD4, hCV26775267 and hCV26775266, were associated with the quantitative phenotypes generated from the ADHD symptoms (corrected P-values = 0.012 for both SNPs). The correlations between the ADHD symptoms and quantitative phenotype revealed that inattentive symptoms had a strong influence on the generated phenotype. Subsequent family-based association test-principal components (FBAT-PC) analyses using inattentive symptoms only also had significant associations. SNPs in the promoter region of DRD4 are associated with the phenotypes generated from ADHD symptoms. The strong correlation of the inattentive symptoms with these quantitative phenotypes and the subsequent FBAT-PC analyses suggest this region is primarily associated with inattentive symptoms. This analysis adds to previous findings by suggesting that variants at these loci may be specifically associated with inattentive symptoms.

Partial replication of a DRD4 association in ADHD individuals using a statistically derived quantitative trait for ADHD in a family-based association test

BACKGROUND

Previous research found an association between single nucleotide polymorphisms (SNPs) in the promoter region of DRD4 and statistically derived phenotypes generated from attention-deficit/hyperactivity disorder (ADHD) symptoms. We sought to replicate this finding by using the same methodology in an independent sample of ADHD individuals.

METHODS

Four SNPs were genotyped in and around DRD4 in 2631 individuals in 642 families. We developed a quantitative phenotype at each SNP by weighting nine inattentive and nine hyperactive-impulsive symptoms. The weights were selected to maximize the heritability at each SNP. Once a quantitative phenotype was generated at each SNP, the screening procedure implemented in PBAT was used to select and test the five SNPs/genetic model combinations with the greatest power to detect an association for DRD4.

RESULTS

One of the four SNPs was associated with the quantitative phenotypes generated from the ADHD symptoms (corrected p-values = .02). A rank ordering of the correlation between each of the ADHD symptoms and the quantitative phenotype suggested that hyperactive-impulsive symptoms were more strongly correlated with the phenotype; however, including inattentive symptoms was necessary to achieve a significant result.

CONCLUSIONS

This study partially replicated a previous finding by identifying an association between rs7124601 and a quantitative trait generated from ADHD symptoms. The rs7124601 is in linkage disequilibrium (LD) with the SNPs identified previously. In contrast to the previous study, this finding suggests that both hyperactive-impulsive and inattentive symptoms are important in the association.

Evidence for an Association of the Dopamine D5 Receptor Gene on Age at Onset of Attention Deficit Hyperactivity Disorder

The purpose of this study was to determine whether the single nucleotide polymorphisms (SNPs) within candidate genes for attention deficit hyperactivity disorder (ADHD) are associated with the age at onset for ADHD. One hundred and forty-three SNPs were genotyped across five candidate genes (DRD5, SLC6A3, HTR1B, SNAP25, DRD4) for ADHD in 229 families with at least one affected offspring. SNPs with the highest estimated power to detect an association with age at onset were selected for each candidate gene, using a power-based screening procedure that does not compromise the nominal significance level. A time-to-onset analysis for family-based samples was performed on these SNPs to determine if an association exists with age at onset for ADHD. Seven consecutive SNPs surrounding the D5 dopamine receptor gene (DRD5), were associated with the age at onset for ADHD; FDR adjusted q-values ranged from 0.008 to 0.023. This analysis indicates that individuals with the risk genotype develop ADHD earlier than individuals with any other genotype. A haplotype analysis across the 6 significant SNPs that were in linkage disequilibrium with one another, CTCATA, was also found to be significant (p-value = 0.02). We did not observe significant associations with age at onset for the other candidate loci tested. Although definitive conclusions await independent replication, these results suggest that a variant in DRD5 may affect age at onset for ADHD.

A study of how socioeconomic status moderates the relationship between SNPs encompassing BDNF and ADHD symptom counts in ADHD families

Recent animal research suggests that brain-derived neurotrophic factor (BDNF), may mediate response to different environmental stimuli. In this paper, we evaluated the possible role of BDNF as a moderator of attention deficit hyperactivity disorder (ADHD) in the context of different socioeconomic classes. We genotyped ten single nucleotide polymorphisms (SNPs) in and around BDNF in 229 families and evaluate whether there are SNP-by-socioeconomic status (SES) interactions for attention deficit hyperactivity. We developed three quantitative phenotypes for ADHD from nine inattentive and nine hyperactive-impulsive symptoms that were used in SNP-by-SES interaction analyses using a new methodology implemented in the computer program PBAT. Findings were adjusted for multiple comparisons using the false discovery rate. We found multiple significant SNP-by-SES interactions using the inattentive symptom count. This study suggests that different SES classes may modify the effect of the functional variant(s) in and around BDNF to have an impact on the number of ADHD symptom counts that are observed. The two exons within BDNF represent potential functional variants that may be causing the observed associations.

Impaired temporal resolution of visual attention and dopamine beta hydroxylase genotype in attention-deficit/hyperactivity disorder

BACKGROUND

Dopamine beta hydroxylase (DbetaH) catalyzes the conversion of dopamine to noradrenaline. Attention-deficit/hyperactivity disorder (ADHD) has been associated with the A2 allele of a Taq I polymorphism of the DBH gene. Since catecholamines regulate visual attention, we examined whether participants with ADHD were impaired on a task requiring temporal attention and how DBH genotype influenced temporal attention in ADHD.

METHODS

Thirty-seven children and adolescents with ADHD and 52 matched, normal control subjects participated. Participants were presented with two visual stimuli, separated in time by either 50, 100, or 200 milliseconds, and were asked to judge the temporal order of their onset. Genotypes for the Taq 1 polymorphism were available for 33 of the ADHD participants.

RESULTS

Attention-deficit/hyperactivity disorder participants were more error prone than control subjects, particularly when stimuli were presented close together in time (i.e., at the 50 milliseconds asynchrony). Moreover, ADHD individuals homozygous for the A2 allele performed more poorly than those without this allele, and this difference was accentuated at the 50 milliseconds asynchrony.

CONCLUSIONS

Attention-deficit/hyperactivity disorder participants have an impaired rate of perceptual processing for rapidly presented visual events. Deficits in the temporal resolution of visual attention in ADHD are associated with the A2 allele of the Taq I DBH polymorphism or another variant with which it is in linkage disequilibrium.

Attention-deficit hyperactivity disorder in girls: epidemiology and management

Attention-deficit hyperactivity disorder (ADHD) in girls is a topic of growing research and clinical interest. For many years, girls with ADHD have been ignored and overshadowed by hyperkinetic and impulsive boys, but they are now attracting interest in an effort to understand the similarities and differences in the prevalence, symptoms, familial risk, comorbidities and treatment of ADHD in the two sexes. A review of past and current literature finds that the symptoms of ADHD are not sex specific, but that identification of girls with ADHD is hampered by parental and teacher bias, and confusion. Girls are more likely to be inattentive without being hyperactive or impulsive, compared with boys. Girls and boys share the same familial risk patterns, as well as similar, although not identical, comorbidity or impairment patterns. The risk of non-treatment is as great in girls as it is in boys; up to 70-80% of identified children will have persistent symptoms and impairment that extends into adolescence and adulthood. Treatment modalities are equally effective in girls and boys. Stimulants, non-stimulants and behavioural modalities are the mainstays of effective treatment.

Association of attention-deficit/hyperactivity disorder with serotonin 4 receptor gene polymorphisms in Han Chinese subjects

Attention-deficit/hyperactivity disorder (ADHD) is an important public health problem. Although serotonin is believed to be an important neurotransmitter in the etiology of this disorder, it remains unclear which specific 5-HT receptors are involved in regulating the symptoms of ADHD. Previous studies have provided favorable evidence for the association of ADHD with both the serotonin transporter gene and serotonin 1B receptor gene. To further investigate the role of other genes of the serotonergic pathway in ADHD, the current study examined variants of the serotonin 4 receptor gene in a relatively large sample of ADHD nuclear families. The T allele of the 83097 C>T polymorphism of HTR4 showed a tendency of preferential transmission to probands with ADHD (chi(2)=2.699, P=0.100). When haplotype TDT analysis of HTR4 was performed, we further found that the C/G haplotype of the 83097 C>T and 83198 A>G polymorphisms (chi(2)=8.783, P=0.003) and the C/G/C haplotype of these and the -36 C>T polymorphism (chi(2)=5.762, P=0.016) were under-transmitted to probands with ADHD. These results suggest that the HTR4 gene may play a role in the genetic predisposition to ADHD.

Family Correlates of Oppositional and Conduct Disorders in Children With Attention Deficit/Hyperactivity Disorder

Comorbidities among children with ADHD are key determinants of treatment response, course, and outcome. This study sought to separate family factors (parental psychopathology and parenting practices) associated with comorbid Oppositional Defiant Disorder (ODD) from those associated with Conduct Disorder (CD) among children with Attention Deficit/Hyperactivity Disorder. Clinic-referred families (n = 149) were diagnosed using DSM-IV criteria. Parents completed measures of parenting practices. Comorbid ODD and CD were significantly associated with maternal negative/ineffective discipline. Comorbid CD, but not ODD, was significantly associated with lack of maternal warmth and involvement, paternal negative/ineffective discipline, and with paternal Antisocial Personality Disorder (APD). However, the risk of CD posed by parenting appeared concentrated among children without a father having APD. While consistent discipline appears important for addressing comorbid ODD and CD, paternal psychopathology and the quality of the relationship between mother and child may pose risk specifically for comorbid CD. Efforts to prevent and/or treat CD should consider not only provision of structure and prudent discipline, but also the affective qualities of the relationship between the primary caretaker and child.

Association of the dopamine transporter (DAT1) 10/10-repeat genotype with ADHD symptoms and response inhibition in a general population sample

Association between attention-deficit hyperactivity disorder (ADHD) and the 10-repeat allele of the dopamine transporter gene (DAT1) has been reported in independent clinical samples using a categorical clinical definition of ADHD. The present study adopts a quantitative trait loci (QTL) approach to examine the association between DAT1 and a continuous measure of ADHD behaviours in a general-population sample, as well as to explore whether there is an independent association between DAT1 and performance on neuropsychological tests of attention, response inhibition, and working memory. From an epidemiological sample of 872 boys aged 6-11 years, we recruited 58 boys scoring above the 90th percentile for teacher reported ADHD symptoms (SWAN ADHD scale) and 68 boys scoring below 10th percentile for genotyping and neuropsychological testing. A significant association was found between the DAT1 homozygous 10/10-repeat genotype and high-scoring boys (chi(2)square=4.6, P<0.03; odds ratio=2.4, 95% CI 1.1-5.0). Using hierarchical linear regression, a significant independent association was found between the DAT1 10/10-repeat genotype and measures of selective attention and response inhibition after adjusting for age, IQ, and ADHD symptoms. There was no association between DAT1 and any component of working memory. Furthermore, performance on tasks of selective attention although associated with DAT1 was not associated with SWAN ADHD high scores after controlling for age and IQ. In contrast, impairment on tasks that tapped sustained attention and the central executive component of working memory were found in high-scoring boys after adjusting for age and IQ. The results suggest that DAT1 is a QTL for continuously distributed ADHD behaviours in the general population and the cognitive endophenotype of response inhibition.

Serotonin 5-HT1B receptor gene and attention deficit hyperactivity disorder in Chinese Han subjects

Serotonin is an endogenous neurotransmitter that regulates aggressive and impulsive behavior and may be involved in the development of attention deficit hyperactivity disorder (ADHD). 5-HT1B knockout mice display hyperactivity, increased exploratory activity and aggression, reduced anxiety, increased vulnerability to cocaine self-administration, and elevated alcohol consumption. Many of these same behaviors are seen in patients with ADHD. Prior studies reported excess transmission of the 861G allele of 5-HT1B to ADHD offspring. We used the transmission disequilibrium test (TDT) and haplotype analysis to investigate the A-161T and G861C polymorphisms in the 5-HT1B receptor gene in ADHD trios from the Chinese Han population. We found no association with ADHD but did find a tendency for excess transmission of the 861G allele (chi(2) = 3.766, P = 0.052) and the G/A haplotype (chi(2) = 2.925, df = 1, P = 0.087), and under-transmission of C/A haplotype (chi(2) = 3.707, df = 1, P = 0.054) to offspring with inattentive ADHD.

Catechol-O-methyltransferase (COMT) Val108/158 Met polymorphism does not modulate executive function in children with ADHD

Background

An association has been observed between the catechol-O-methyltransferase (COMT) gene, the predominant means of catecholamine catabolism within the prefrontal cortex (PFC), and neuropsychological task performance in healthy and schizophrenic adults. Since several of the cognitive functions typically deficient in children with Attention Deficit Hyperactivity Disorder (ADHD) are mediated by prefrontal dopamine (DA) mechanisms, we investigated the relationship between a functional polymorphism of the COMT gene and neuropsychological task performance in these children.

Methods

The Val^108/158 Met polymorphism of the COMT gene was genotyped in 118 children with ADHD (DSM-IV). The Wisconsin Card Sorting Test (WCST), Tower of London (TOL), and Self-Ordered Pointing Task (SOPT) were employed to evaluate executive functions. Neuropsychological task performance was compared across genotype groups using analysis of variance.

Results

ADHD children with the Val/Val, Val/Met and Met/Met genotypes were similar with regard to demographic and clinical characteristics. No genotype effects were observed for WCST standardized perseverative error scores [F_2,97 = 0.67; p > 0.05], TOL standardized scores [F_2,99 = 0.97; p > 0.05], and SOPT error scores [F_2,108 = 0.62; p > 0.05].

Conclusions

Contrary to the observed association between WCST performance and the Val^108/158 Met polymorphism of the COMT gene in both healthy and schizophrenic adults, this polymorphism does not appear to modulate executive functions in children with ADHD.

Association of the 480 bp DAT1 allele with methylphenidate response in a sample of Irish children with ADHD

Several studies have implicated the dopamine transporter gene (DAT1) as conferring susceptibility to attention deficit hyperactivity disorder (ADHD), in particular, a VNTR situated at the 3' end of the gene. In addition, the 10-repeat VNTR allele associated with ADHD has been reported to be associated with an over-active transporter protein (DAT). Thus children possessing this variant might be particularly responsive to methylphenidate, a drug known to act by blocking DAT. We have examined this hypothesis and now report an association between the 10-repeat VNTR DAT1 polymorphism and retrospectively rated methylphenidate response in a sample of 119 Irish children with ADHD (chi(2) = 7.918, df = 1, P = 0.005). Our findings suggest a role for the 10-repeat DAT1 risk allele in medication response and may help to predict positive clinical outcome in ADHD.

The dopaminergic system in attention deficit/hyperactivity disorder

Numerous studies have shown the importance of the mesocorticolimbic dopamine system in the pathophysiology of attention deficit/hyperactivity disorder. However, there has been inconsistency in the findings of those studies. Varied and sometimes contradictory interpretation has been made on the basis of similar results. It is, therefore, still unclear whether the dopaminergic system is hypo- or hyperfunctioning in attention deficit/hyperactivity disorder. The majority of the functional brain imaging studies in both clinical and experimental settings support hypofunction of the basal ganglia which receive abundant dopaminergic afferent. The experimental studies, using dopamine-depleted animals, also support the hypodopaminergic hypothesis, whereas recent studies with the dopamine transporter knockout/knockdown mouse suggest hyperdopaminergic function as the underlying abnormality. In this review we attempt to clarify the issues raised by previous neuroimaging and functional neuroimaging studies. Research involving animal models with genetic traits, genetic manipulation or with brain lesions is analysed, concentrating on the significance of the dopaminergic system in the abnormal behavior of attention deficit/hyperactivity disorder. In addition, the functional state of the dopaminergic system is considered through the speculated mechanism of psychostimulant therapy of the disorder. No final conclusions have been reached regarding the pathological, biochemical and physiological mechanisms responsible for various symptoms. Inconsistency in the findings and their interpretations may indicate the heterogeneity of the pathogenesis of this syndrome.

Family-based and case-control association studies of catechol-O-methyltransferase in attention deficit hyperactivity disorder suggest genetic sexual dimorphism

Attention deficit hyperactivity disorder (ADHD) is the most common childhood-onset behavioral disorder. Boys are more often affected than girls. Family, twin, and adoption studies have supported a strong genetic basis. Some studies show that a catechol-O-methyltransferase (COMT) polymorphism affecting enzyme activity was associated with personality characteristics and diseases, such as novelty-seeking personality, substance abuse, and heroin addiction, whose features are similar to ADHD or are associated with ADHD. These findings suggest that the COMT gene may be a candidate gene for ADHD. TDT, HHRR, and case-control association studies were conducted within a sample of 202 nuclear ADHD families, 340 ADHD cases, and 226 controls in the Han Chinese population. Diagnoses and ADHD subtypes were ascertained according to DSM-IV criteria using American Clinical Diagnostic Interviewing Scales. The HHRR analysis suggested that the low enzyme-activity COMT Met allele was preferentially transmitted to ADHD boys (160 trios, chi(2) = 3.858, P = 0.05, df = 1) but not girls. This association is particularly pronounced among male ADHD probands without any comorbidity (50 trios, HHRR: chi(2) = 5.128, P = 0.024, df = 1; TDT: chi(2) = 4.558, P = 0.033, df = 1), especially the ADHD-I subtype (32 trios, HHRR: chi(2) = 5.792, P = 0.016, df = 1; TDT: chi(2) = 5.333, P = 0.021, df = 1). The case-control study revealed that the Val allele was more frequent in females meeting ICD-10 or DSM-IV criteria for ADHD than in female controls (86 and 79.5%, respectively, chi(2) = 4.059, P = 0.044, df = 1). Although these results suggest the COMT gene exerts some influence on the risk for ADHD in the Han Chinese population, given the potential for Type I error, these findings require replication before drawing definitive conclusions.

Long-term stability of the Child Behavior Checklist in a clinical sample of youth with attention deficit hyperactivity disorder

Evaluated the long-term stability of the Child Behavior Checklist (CBCL) in a longitudinal clinical sample of youth with attention deficit hyperactivity disorder (ADHD), testing the hypothesis that the CBCL scales will show stability over time. Participants were 105 Caucasian, non-Hispanic boys with ADHD between the ages of 6 and 17 assessed at baseline and at a 4-year follow-up. Stability of CBCL scales were computed for dimensional (intraclass correlation coefficients [ICCs], Pearson correlations) and dichotomized scale scores (kappa coefficients and odds ratios [ORs]). Evidence was found for stability of the categorical and dimensional types of scores, as demonstrated by statistically significant stability of the Pearson correlation coefficients, kappas, and ORs. The robust findings obtained from ICCs and kappa coefficients document substantial stability for CBCL scales over time within individuals with ADHD. These results support the informativeness of the CBCL as a useful measure of longitudinal course in clinical samples of youth with ADHD.

Families of children with attention-deficit/hyperactivity disorder: review and recommendations for future research

This review integrates and critically evaluates what is known about family characteristics associated with childhood Attention-Deficit/Hyperactivity Disorder (ADHD). Evidence suggests that the presence of ADHD in children is associated to varying degrees with disturbances in family and marital functioning, disrupted parent-child relationships, specific patterns of parental cognitions about child behavior and reduced parenting self-efficacy, and increased levels of parenting stress and parental psychopathology, particularly when ADHD is comorbid with conduct problems. However, the review reveals that little is known about the developmental mechanisms that underlie these associations, or the pathways through which child and family characteristics transact to exert their influences over time. In addition, the influence of factors such as gender, culture, and ADHD subtype on the association between ADHD and family factors remains largely unknown. We conclude with recommendations regarding the necessity for research that will inform a developmental psychopathology perspective of ADHD.

Pre-, peri-, and postnatal trauma in subjects with attention-deficit hyperactivity disorder

OBJECTIVE

To review research on pre-, peri-, and postnatal stress and their potential relation to attention-deficit hyperactivity disorder (ADHD).

METHOD

We selected and critically reviewed 51 research reports from the medical and psychology literature, between January 1, 1976 and May 1, 2001, based on the subjects of pre-, peri-, or postnatal stress and ADHD.

RESULTS

Children with ADHD show higher percentages of pre-, peri-, or postnatal insult, compared with unaffected children; however, the relative influence of various factors is still controversial.

CONCLUSIONS

The etiology of ADHD encompasses genetic and environmental factors. Pre-, peri-, and postnatal stressors are environmental factors that may play a role in its etiology. Future research should carefully examine interactions between genetic predisposition and environmental factors as etiologies of ADHD.

Clinical and molecular genetics of ADHD and Tourette syndrome. Two related polygenic disorders

ADHD is a polygenic disorder due to the additive effect of genes affecting dopamine, norepinephrine, serotonin, GABA, and other neurotransmitters. Some of the specific loci involved are dopamine genes--DRD2, DRD4, DRD5, and the dopamine transporter; norepinephrine (NE) and epinephrine (EPI) genes--dopamine beta-hydroxylase, ADRA2A, ADRA2C, PNMT, norepinephrine transporter, MAOA, COMT; serotonin genes--TDO2, HTR1A, HTR1DA, serotonin transporter; GABA genes--GABRB3; androgen receptor and other genes. This model is consistent with all of the present knowledge about ADHD including (a) the increased frequency of ADHD in the relatives of ADHD probands, (b) the presence of a wide spectrum of comorbid behaviors (depression, anxiety, learning, conduct, oppositional-defiant, conduct and substance abuse disorders) in ADHD probands and their relatives on both parental sides, (c) the close relationship to Tourette syndrome (TS), (d) the failure to find the genes for TS using linkage analysis, (e) the brain imaging studies showing hypometabolism of the frontal lobes, (f) the relationship between dopamine D2 receptor density and regional blood flow, (g) the correlation between tics and dopamine D2 receptor density in TS, (h) the motor hyperactivity of dopamine transporter and dopamine D3 receptor gene knockout mice, (i) the LeMoal and Shaywitz dopamine deficiency animal models of ADHD, (j) the NE models of ADHD, (k) the failure to explain ADHD on the basis of any single neurotransmitter defect, (l) the response of ADHD to dopamine and alpha 2-adrenergic agonists, (m) the small percentage of the variance of specific behaviors accounted for by each gene, and numerous other aspects of ADHD. The implications of the polygenic model for the understanding, diagnosis and treatment of ADHD and TS, as well as other psychiatric disorders, are reviewed.

Haplotype study of three polymorphisms at the dopamine transporter locus confirm linkage to attention-deficit/hyperactivity disorder

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is often treated using methylphenidate, a psychostimulant that inhibits the dopamine transporter. This led E.H. Cook and colleagues to consider the dopamine transporter locus (DAT1) as a primary candidate gene for ADHD. That group reported a significant association between ADHD and the 480-base pair (bp) allele of the variable number of tandem repeats (VNTR) polymorphism located in the 3' untranslated region of the DAT1 gene. This association was later replicated in additional studies.

METHODS

The DAT1 gene has additional common polymorphisms in intron 9 and exon 9. We investigated the possibility of linkage of DAT1 and ADHD using the VNTR polymorphism and two additional common polymorphisms in 102 nuclear families with an ADHD proband. Using the transmission disequilibrium test, we examined the transmission of the alleles of each of these polymorphisms, as well as the haplotypes of the polymorphisms.

RESULTS

We did not observe significant evidence for the biased transmission of the alleles of either the VNTR or the additional two polymorphisms when examined individually, although there was a trend for the biased transmission of the 480-bp allele of the VNTR. When we examined the haplotypes of the three polymorphisms we found significant evidence for biased transmission of one of the haplotypes containing the 480-bp VNTR allele. We also genotyped six additional DNA sequence variants of the DAT1 gene. However, these variants were not sufficiently polymorphic in our sample to be informative. Two of the DNA variants that result in an amino acid change, Ala559Val and Glu602Gly, were not observed in our sample.

CONCLUSIONS

Our results support previous findings of an association between the DAT1 gene and ADHD.

Familial aggregation of ADHD characteristics

Patterns of familial aggregation of ADHD symptoms in parents of ADHD and non-ADHD children were examined. Within the ADHD sample, symptom aggregation was examined as a function of biological relationship, parent and child gender, and children's comorbid diagnoses. Participants consisted of parents of 579 children with ADHD, Combined Type participating in the multimodal treatment study of children with ADHD and parents of 288 normal control participants. Adult symptoms of ADHD were measured by both self-report and report of a significant other. Results indicated that the parents of children with ADHD had higher ratings of inattention/cognitive problems, hyperactivity/restlessness, impulsivity/emotional lability, and lower self-concept than parents of children without ADHD on both self-report and other-report ratings. Within the ADHD sample of children, other-report ratings of inattention/cognitive problems and impulsivity/emotional lability were higher for biological parents compared to nonbiological parents whereas self-ratings were not related to biological status. These findings support previous research documenting familial aggregation of ADHD and appear to strengthen the hypothesis that there is a genetic contribution to ADHD.

Toward guidelines for pedigree selection in genetic studies of attention deficit hyperactivity disorder

Converging evidence from family, twin, and adoption studies points to a substantial genetic component of the etiology of attention deficit hyperactivity disorder (ADHD). These data about ADHD have motivated molecular genetic studies of the disorder, which have produced intriguing but somewhat conflicting results. Some studies have reported associations with candidate genes and others not. Our review of the literature shows that one problem facing molecular genetic studies of ADHD is that its recurrence risk to first-degree relatives is only about five times higher than the population prevalence. This suggests that, to produce consistently replicated results, molecular genetic studies should either use much larger samples or should select those families in which genes exert the largest effect. Risch [(1990a) Am J Hum Genet 46:222-228; (1990b) Am J Hum Genet 46:229-241] proved that the statistical power of a linkage study increases with the magnitude of risk ratios (lambda's) computed by dividing the affection rate among each relative type to the rate of affection in the population. Our prior work suggests two dimensions of genetic heterogeneity that might be useful for selecting ADHD subjects for molecular genetic studies: comorbidity with conduct disorder and persistence of ADHD into adolescence. This paper shows that these sub-phenotypes are useful for molecular genetic studies because (1) they have much higher empirical lambda values and (2) they affect a substantial minority of ADHD patients.

Diagnosis of attention-deficit/hyperactivity disorder in the office

The evaluation of the child with ADHD can be a complex and time-consuming process. Because there are no specific diagnostic tests, the physician must rely on the old standard of history and observation. An approach to diagnosis has been outlined in this article, which views ADHD as one of many clinical expressions of a more generalized impairment of neurologic processing. This approach suggest that four separate areas should be investigated: family and medical history, behavior, cognition, and coordination, while searching for signs of impairment in each area. This can provide a framework for the private practitioner to effectively and efficiently evaluate a child for ADHD within a busy office practice.

Evaluation of ADHD typology in three contrasting samples: a latent class approach

OBJECTIVE

To identify subtypes of attention-deficit/hyperactivity disorder (ADHD) and characterize them as either categorical or continuous; to investigate familial resemblance for ADHD among sibling pairs; and to test the robustness of all results by using contrasting data sets.

METHOD

Latent class analysis was applied to the ADHD symptom profiles obtained from parents or best informant about their offspring in 3 samples: a population-based set of female adolescent twins (724 monozygotic pairs, 594 dizygotic pairs) and male (N = 425) and female (N = 430) child and adolescent offspring ascertained from high-risk alcoholic families.

RESULTS

Latent class analysis revealed 2 categories of clinically significant ADHD which were replicated in all 3 study groups: a subtype with high endorsements of ADHD inattention symptoms and a second combined type with high endorsements of both inattention and hyperactivity-impulsivity items. Both appeared to be continuous across all 3 data groups. The high-risk families contained a class in which members heavily endorsed the ADHD "fidget" item but not other ADHD items. A large proportion of the monozygotic sibs (80%) versus a smaller proportion of dizygotic sibs (52%) were assigned to the same latent class. Among the high-risk children and adolescents, 51% of the female and 41% of the male siblings were concordant for class membership.

CONCLUSIONS

The pattern of latent classes suggested that ADHD consists of an inattentive and a combined subtype, within each of which lies a dimensional domain. These analyses further support that genetic factors are significant determinants of latent class membership.

Attention deficit hyperactivity disorder: an evolutionary perspective

Attention deficit hyperactivity disorder (ADHD) affects a significant portion of the population--some 5% of all school-aged children--and approximately half of these individuals continue to show the full disorder in adulthood. Recent studies point to a strong genetic component in the etiology of this disorder. Questions have been raised as to the relatively high prevalence of this condition in the population, given its apparent maladaptive nature in present-day society. In this article, we review and discuss three theories regarding the possible adaptive function of ADHD: the hunter, fighter, and wader theories. Although no theory entirely explains the occurrence of ADHD, it is worthwhile to note that, at least historically, ADHD may have served an adaptive function and may have been selected by the environment for survival.

Is season of birth a risk factor for attention-deficit hyperactivity disorder?

OBJECTIVE

To investigate seasonal variations in the birth patterns of children with attention-deficit hyperactivity disorder (ADHD) in reference to a group of normal control children, attending to issues of comorbidity, familiality, and learning disability.

METHOD

Subjects were boys with DSM-III-R ADHD (n = 140) and normal controls (n = 120). The ADHD children were stratified by the presence of comorbid psychiatric disorders, learning disability, and family history of ADHD, and logistic regression was used to estimate relative risks.

RESULTS

No statistically major effect for season of birth was observed in the comparison of ADHD and control children. However, significant effects were found for September births for ADHD children with learning disability (odds ratio = 5.4) and for ADHD children without psychiatric comorbidity (odds ratio = 4.5). A trend was also noted for winter births in ADHD children with learning disabilities, no psychiatric comorbidity, and positive family history for ADHD.

CONCLUSIONS

These preliminary results suggest that there may be a seasonal pattern of birth for subtypes of ADHD. If season of birth serves as a proxy for the timing of seasonally mediated viral infections, it may lead to a greater understanding of the etiology and pathophysiology of ADHD.

Families of children with attention deficit hyperactivity disorder: a review

OBJECTIVES

1) To review the evidence of attention deficit hyperactivity disorder (ADHD) and other conditions in family members (siblings and parents) of children with ADHD and determine the importance of genetic and environmental factors in this condition. 2) To describe the prospective 10-year follow-up of 65 families with ADHD children and 43 families of matched normal controls. 3) To review various studies that have looked at parent-child interactions with ADHD children on and off stimulant medication, and such interactions over time. The paper thus provides an overview of family pathology and functioning of families of ADHD children over time.

METHOD

The paper outlines twin, sibling, family and adoption studies with regard to possible genetic and environmental factors in ADHD. It also presents data of a prospective 10-year follow-up of 65 families with ADHD children and 43 families of normal controls. This family study evaluated sociocultural factors, child rearing practices, health of family members and relationships, as well as the parental view of the child's functioning over time.

RESULTS

A review of the literature suggests that ADHD has a strong genetic component, but that environmental factors also play an important role. Families of children with ADHD have more problems than families of normal controls, but these problems improve as the child with ADHD grows up and leaves home. Families of ADHD subjects can appreciate positive as well as negative changes in their children over time. Generally, family interactions with children with ADHD are problematic but improve when the child is on medication and when the child becomes an adult.

CONCLUSIONS

This condition has strong genetic underpinnings; therefore, diagnosing and treating family members (parents and siblings) as well as the child with ADHD is important in improving parent-child interactions and better long-term outcome for the child and his or her family.

Attention deficit disorder in adults and nicotine dependence: psychobiological factors in resistance to recovery?

The addictive nature of nicotine appears to depend on a number of psychobiological factors. This study explores the psychoactive effects of nicotine in relationship to the particular dysphoric aspects of Attention Deficit Disorder as a coincident factor in nicotine dependence and resistance to treatment. The psychological and behavioral effects of nicotine directly correspond to reduction in symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD) and the neurochemical effects of nicotine are qualitatively similar to stimulant medications used to treat ADHD. Aspects of the treatment of nicotine or other addictions in such comorbid situations are discussed in the context of self-medication.

Polygenic inheritance of Tourette syndrome, stuttering, attention deficit hyperactivity, conduct, and oppositional defiant disorder: the additive and subtractive effect of the three dopaminergic genes--DRD2, D beta H, and DAT1

Polymorphisms of three different dopaminergic genes, dopamine D2 receptor (DRD2), dopamine beta-hydroxylase (D beta H), and dopamine transporter (DAT1), were examined in Tourette syndrome (TS) probands, their relatives, and controls. Each gene individually showed a significant correlation with various behavioral variables in these subjects. The additive and substractive effects of the three genes were examined by genotyping all three genes in the same set of subjects. For 9 of 20 TS associated comorbid behaviors there was a significant linear association between the degree of loading for markers of three genes and the mean behavior scores. The behavior variables showing the significant associations were, in order attention deficit hyperactivity disorder (ADHD), stuttering oppositional defiant, tics, conduct, obsessive-compulsive, mania, alcohol abuse and general anxiety-behaviors that constitute the most overt clinical aspects of TS. For 16 of the 20 behavior scores there was a linear progressive decrease in the mean score with progressively lesser loading for the three gene markers. These results suggest that TS, ADHD, stuttering oppositional defiant and conduct disorder, and other behaviors associated with TS, are polygenic, due in part to these three dopaminergic genes, and that the genetics of other polygenic psychiatric disorders may be deciphered using this technique.

A pilot family study of childhood-onset mania

OBJECTIVE

To investigate the familial association of attention-deficit hyperactivity disorder (ADHD) and bipolar disorder (BPD) among the first-degree relatives of children with comorbid ADHD and BPD.

BACKGROUND

In contrast to a growing body of literature on childhood non-bipolar depression, little is known about childhood BPD. Among the explanations accounting for the lack of recognition and identification of these children is the symptomatic overlap of BPD with ADHD. Family-genetic studies provide information external to the clinical picture and thus are uniquely suited to clarify such issues of diagnostic comorbidity.

METHOD

Structured diagnostic interviews were used to obtain DSM-III-R psychiatric diagnoses on first-degree relatives (n = 46) of referred children (aged < or = 12 years) satisfying diagnostic criteria for mania using the Schedule for Affective Disorders and Schizophrenia for School-Age Children-Epidemiologic Version (n = 16). For comparison, diagnostic information on the first-degree relatives of non-bipolar ADHD children and control children was examined.

RESULTS

The results show high rates of comorbidity between BPD and ADHD in children and high rates of both BPD and ADHD in the first-degree relatives of these children. Moreover, ADHD and BPD cosegregated among the relatives of children with BPD.

CONCLUSIONS

These findings, which are consistent with the authors' prior study of children with ADHD, provide family-genetic evidence for the validity of BPD and ADHD when they exist comorbidly in children. Moreover, they suggest that the comorbid condition of ADHD+BPD may be a distinct nosological entity.

How reliable are maternal reports of their children's psychopathology? One-year recall of psychiatric diagnoses of ADHD children

OBJECTIVE

Although childhood psychiatric diagnoses often rely on maternal reports, little is known about their long-term reliability and diagnostic accuracy. Thus, the authors sought to examine these psychometric features in a cohort of ADHD and control children.

METHOD

The sample consisted of 140 referred children with ADHD and 120 normal controls. The authors compared childhood diagnoses based on maternal reports of their children's psychopathology at this baseline assessment with those collected 1 year later.

RESULTS

Both reliability and accuracy were excellent for ADHD. Reliability and specificity were also excellent for conduct disorder, oppositional defiant disorder, major depression, bipolar disorder, separation anxiety, and multiple anxiety disorders. Reliability and sensitivity were relatively low for simple phobia, social phobia, agoraphobia, and overanxious disorder.

CONCLUSIONS

With some exceptions, maternal reports of their children's psychopathology provided a reliable and accurate means of assessment. Generally, maternally derived diagnoses were less accurate for internalizing compared with externalizing disorders. However, specificity was high for all diagnoses, suggesting that mothers were not biased to report symptoms that had not occurred.