Serotonin Syndrome in Children and Adolescents Exposed to Selective Serotonin Reuptake Inhibitors - A Review of Literature

OBJECTIVE

The use of selective serotonin reuptake inhibitors (SSRIs) in children and adolescents is increasing in Canada and internationally. While SSRIs are known for their generally well tolerated side effect profile, serotonin syndrome can arise as a severe complication. The objective of this study is to review literature on SSRI-related serotonin syndrome in the pediatric population.

METHODS

An extensive review of literature on "serotonin syndrome" is conducted using PubMed from inception to March 2019, focusing on subjects zero to 18 years of age. Descriptive statistics are used for data analysis.

RESULTS

The search yielded N=337 references and N=18 studies are included, all of which are case reports. The cases encompass ethnically diverse subjects ranging from 4 to 18 years of age, diagnosed with serotonin syndrome after exposure to SSRI agents. Most common presenting symptoms are confusion, agitation, tachycardia, hypertension, hyperreflexia, rigidity, and tremor. Serotonin syndrome manifested from SSRI monotherapy (7/18; 3 after first dose), when SSRI was combined with another serotonergic agent (6/18), or after an overdose (5/18). Risk factors include high starting doses and co-prescription. Changing multiple medications at the same time adds to diagnostic challenges.

CONCLUSIONS

Serotonin syndrome is a severe adverse drug reaction associated with SSRI, and can be associated with diverse presentations in the pediatrics population and diagnostic challenges. Clinicians are recommended to be vigilant in the monitoring and recognition of serotonin syndrome.

Estimation of enteric methane emission factors for Ndama cattle in the Sudanian zone of Senegal

Methane (CH₄) emission estimations for cattle in Sub-Saharan Africa (SSA) reflect limited production levels and diets that are high in cellulose forage. However, data on these livestock systems is lacking for their accurate evaluation. To provide guidance for climate change mitigation strategies in Senegal, it is necessary to obtain reliable estimates of CH₄ emissions from Ndama cattle reared in grazing systems, which is the predominant cattle system in the country. The objective of this study was to determine the annual methane emission factor (MEF) for enteric fermentation of Ndama cattle following the IPCC Tier 2 procedure. Our estimated annual MEF at the herd scale was 30.8 kg CH₄/TLU (30.7 kg CH₄/head/yr for lactating cows and 15.1 kg CH₄/head/yr for other cattle). These values are well below the default IPCC emission factor (46 and 31 kg CH₄/head/yr for dairy and other cattle, respectively) proposed in the Tier 1 method for Africa. Our study showed that feed digestibility values differ with season (from 46 to 64%). We also showed that cattle lose weight and adapt to lower feed requirements during the long dry season, with a resulting major reduction in methane emissions. The results of this work provide a new framework to re-estimate the contribution of grazing systems to methane emissions in Africa.

Stimulant Withdrawal in a Child with Autism Spectrum Disorder and ADHD - A Case Report

OBJECTIVE

To consider whether the concepts of tolerance and withdrawal to stimulant medications apply to a preadolescent female, affected by autism spectrum disorder (ASD) and treated for associated attention-deficit/hyperactivity disorder (ADHD).

METHODS

We describe the case history and review scientific English language literature pertaining to acute withdrawal effects associated with methylphenidate and amphetamine derivatives in children.

RESULTS

An 11-year-old female with ASD and ADHD referred to our clinic experienced vomiting, headaches, and light sensitivity following abrupt discontinuation of methylphenidate; she subsequently presented with migraines and marked malaise immediately after a dose reduction in lisdexamfetamine. Evidence supports the notion that ADHD symptoms in children with ASD can be effectively treated with methylphenidate; however, beneficial effects are less robust relative to children with a primary ADHD diagnosis. Children affected by ASD are also more susceptible to adverse effects. Literature on withdrawal from stimulants in children is limited to case studies; in contrast, in the adult population more information is available, especially in adults with substance abuse disorders. Adults experiencing stimulant withdrawal often experience depression, fatigue, changes in appetite, and insomnia or hypersomnia.

CONCLUSIONS

We argue that tolerance to stimulants was conceivably developing in this young female, and consequently discontinuation of methylphenidate and dose reduction of lisdexamfetamine resulted in withdrawal symptoms. Children with ASD are more sensitive to stimulant medications and we wonder whether this extends to an increased sensitivity to developing tolerance to stimulant medication. Clinicians ought to be vigilant about the emergence of symptomology suggestive of withdrawal phenomena following stimulant discontinuation.

Depression Screening and Health Outcomes in Children and Adolescents: A Systematic Review

OBJECTIVE

Depression screening among children and adolescents is controversial. In 2009, the United States Preventive Services Task Force first recommended routine depression screening for adolescents, and this recommendation was reiterated in 2016. However, no randomized controlled trials (RCTs) of screening were identified in the original 2009 systematic review or in an updated review through February 2015. The objective of this systematic review was to provide a current evaluation to determine whether there is evidence from RCTs that depression screening in childhood and adolescence improves depression outcomes.

METHOD

Data sources included the MEDLINE, MEDLINE In-Process, EMBASE, PsycINFO, Cochrane CENTRAL and LILACS databases searched February 2, 2017. Eligible studies had to be RCTs that compared depression outcomes between children or adolescents aged 6 to 18 years who underwent depression screening and those who did not.

RESULTS

Of 552 unique title/abstracts, none received full-text review. No RCTs that investigated the effects of screening on depression outcomes in children or adolescents were identified.

CONCLUSIONS

There is no direct RCT evidence that supports depression screening among children and adolescents. Groups that consider recommending screening should carefully consider potential harms, as well as the use of scarce health resources, that would occur with the implementation of screening programs.

Combined Modality Intervention for ADHD With Comorbid Reading Disorders: A Proof of Concept Study

To evaluate the relative efficacy of two reading programs with and without adjunctive stimulant medication for children with attention-deficit/hyperactivity disorder and comorbid reading disorder (ADHD+RD). Sixty-five children (7-11 years in age) were assigned randomly to one of three intensive remedial academic programs (phonologically or strategy-based reading instruction, or general academic strategy and social skills training) in combination with either immediate-release methylphenidate or placebo. Multiple-blind procedures were used for medication/placebo, given twice daily. Children received 35 hours of instruction in 10 weeks, taught by a trained teacher in a separate school classroom, in small matched groups of 2 to 3. Children's behavior and reading abilities were assessed before and after intervention. Stimulant medication produced expected beneficial effects on hyperactive/impulsive behavioral symptoms (reported by classroom teachers) but none on reading. Children receiving a reading program showed greater gains than controls on multiple standardized measures of reading and related skills (regardless of medication status). Small sample sizes precluded interpretation of possible potentiating effects of stimulant medication on reading skills taught in particular reading programs. Intensive reading instruction, regardless of treatment with stimulant medication, may be efficacious in improving reading problems in children with ADHD+RD and warrants further investigation in a large-scale study.

Accuracy of Depression Screening Tools to Detect Major Depression in Children and Adolescents: A Systematic Review

OBJECTIVE

Depression screening among children and adolescents is controversial, and no clinical trials have evaluated benefits and harms of screening programs. A requirement for effective screening is a screening tool with demonstrated high accuracy. The objective of this systematic review was to evaluate the accuracy of depression screening instruments to detect major depressive disorder (MDD) in children and adolescents.

METHOD

Data sources included the MEDLINE, MEDLINE In-Process, EMBASE, PsycINFO, HaPI, and LILACS databases from 2006 to September 30, 2015. Eligible studies compared a depression screening tool to a validated diagnostic interview for MDD and reported accuracy data for children and adolescents aged 6 to 18 years. Risk of bias was assessed with QUADAS-2.

RESULTS

We identified 17 studies with data on 20 depression screening tools. Few studies examined the accuracy of the same screening tools. Cut-off scores identified as optimal were inconsistent across studies. Width of 95% confidence intervals (CIs) for sensitivity ranged from 9% to 55% (median 32%), and only 1 study had a lower bound 95% CI ≥80%. For specificity, 95% CI width ranged from 2% to 27% (median 9%), and 3 studies had a lower bound ≥90%. Methodological limitations included small sample sizes, exploratory data analyses to identify optimal cut-offs, and the failure to exclude children and adolescents already diagnosed or treated for depression.

CONCLUSIONS

There is insufficient evidence that any depression screening tool and cut-off accurately screens for MDD in children and adolescents. Screening could lead to overdiagnosis and the consumption of scarce health care resources.

Epilepsy, Attention-Deficit/Hyperactivity Disorder and Methylphenidate: Critical Examination of Guiding Evidence

OBJECTIVE

Attention-Deficit/Hyperactivity Disorder (ADHD) and epilepsy are commonly comorbid; yet in the psychiatric literature, there is a remarkable paucity of guiding evidence regarding the safety and efficacy of treatment using methylphenidate (MPH) in this population. The objective of this review is to critically appraise evidence regarding the treatment of ADHD in the context of seizure disorders in order to better inform management considerations and practices.

METHOD

A comprehensive search of the Central, Embase, Medline, and Web of Science databases identified 349 references. After a thorough review, only nine relevant references contributing new information and providing reliable and interpretable data were identified; seven were prospective studies (two double-blind placebo controlled trials, five open-label trials) and two were retrospective reviews. Prospective studies were then reviewed in detail, critically appraised, and interpreted.

RESULTS

All studies reported no increase in seizure rates in a majority of participants after exposure to MPH. MPH was effective in treating ADHD symptoms. However, the following major limitations to the studies impede drawing confident conclusions: small sample sizes, lack of uniformity regarding seizure type and severity, seizure-free period pre-stimulant treatment, and low baseline seizure rates.

CONCLUSIONS

Given the academic, social, emotional, and functional impact of untreated ADHD, a watchful approach to the use of MPH in children with stable epilepsy who are impaired by ADHD symptoms is justified.

Methanogenic potential of forages consumed throughout the year by cattle in a Sahelian pastoral area

Methane (CH4) emission from ruminants in African pastoral systems may be affected by intake and type of plants, which vary highly between rainy and dry seasons. In each of two sites located in the semiarid Sahelian area of Senegal, three Gobra zebus were monitored throughout 1 year. A representative sample of their diet was obtained once every month. Diet was mainly composed of grasses, herbaceous legumes, tree and shrub foliage and pods, and dried forage residues. CH4 production and volatile fatty acid (VFA) concentration, which reflects VFA production, were determined in vitro. Crude protein, neutral detergent fibre (NDF) and acid detergent fibre were measured by near-infrared spectrophotometry. CH4 production varied between 24.6 and 35.2 mL/g forage dry matter (DM), being minimal in August (rainy season) and maximal in February (dry season). Seasonal difference disappeared when CH4 was expressed in mL/g NDF. The acetate : propionate ratio varied in the same way as CH4 (3.2 and 4.6 in August and February, respectively); VFA concentration was minimum in March and maximum in September (69.2 and 77.4 mmol/L, respectively). CH4 production was closely related to dietary NDF content (r = 0.82) and to acetate : propionate ratio (r = 0.96). For six successive periods (February to July), plant categories constituting the diet were incubated separately. Reconstituting the CH4 production and VFA concentration in the diet on the basis of the proportion of plant components gave values similar to those of the global diet (33.4 and 34.2 mL CH4/g DM and 75.9 and 70.9 mmol VFA/L, respectively). This result suggests the absence of interaction among plant components on rumen fermentation.

Can virtual fences be used to control grazing sheep?

Virtual fences (VF) are based on sensory cues delivered to domestic animals with the aim of controlling their spatial behaviour without any physical barrier. VF represent an approach for controlling the distribution of free-ranging large herbivores in large rangeland areas where the implementation of human control or the use of physical fencing is made impossible by their cost, environmental concerns or specific regulations. The potential of using VF for sheep was investigated by studying the spatial behaviour of groups of 5 or 32 ewes submitted to a commercial animal-borne VF device aimed at containing them in a defined area in a series of experiments. All tests were performed in pasture alleys virtually divided in their centre by a 4-m-wide warning/punishment zone). The ewes were introduced on one side of the zone, the other side being made attractive by the presence of tall grass (feed attractant), the presence of peers (social attractant) or being made unattractive by the presence of short grass (same feed as in the alley). In a first experiment, ewes were trained in groups of 5 with a feed attractant, following a 3-stage procedure: 30-min adaptation, 90-min training with a visual cue (three white strings above the wire of the VF) and 30-min test without a visual cue. In a second experiment, the test stage was repeated for each group with feed, social and zero attractants. In a third experiment, the test with feed attractant was performed with groups of 32 ewes comprising previously trained and equipped ewes mixed in different percentages of trained: naïve (untrained and unequipped) ewes (100 : 0, 75 : 25, 50 : 50 and 0 : 100%). One year later, this test was repeated with a feed attractant either close (30 m) or far (60 m) from the punishment zone. By increasing the distance to the feed attractant, it was anticipated that this would stimulate the conflict of motivation between feed and peers. Ewes learned readily the concept of VF after a couple of contacts with the punishment zone. In the second experiment in the test with a social attractant, a few trained ewes penetrated the VF to re-associate with peers located in the pen opposite the VF. Expression of the behaviour to challenge or cross the punishment zone differed widely among individuals. In mixed groups, naïve ewes crossed the punishment zone and lead part of their trained peers across the punishment zone, regardless of the distance of the feed attractant from the punishment zone. The results suggest that VF can be used to alter the distribution of grazing sheep within large fenced areas although they cannot replace conventional fences for absolute control.

Stop signal and Conners' continuous performance tasks: test--retest reliability of two inhibition measures in ADHD children

OBJECTIVE

To measure test-retest reliability of the Stop-Signal Task (SST) and the Conners' Continuous Performance Test (CPT) in children with ADHD.

METHODS

12 children with ADHD (age 11.46 +/-1.66) participated in the study. Primary outcome measures were stop-signal reaction time (SSRT) for the SST and CPT's commission errors (%FP). For each participant, we acquired three morning (8:00am) measurements and behavioral observations, separated by two 7-day intervals. Reliability of cognitive measures and behavioral observations was measured using the Intraclass-correlation coefficient (ICC).

RESULTS

ICC values for SSRT and %FP were 0.72. Consistency of behavioral observations was much lower (ICC =0.41).

CONCLUSION

Both the SST and the CPT yielded reliable measurements in ADHD children. Our findings lend further support to using these measures in the study of ADHD.

An innovative child CBT training model for community mental health practitioners in Ontario

OBJECTIVE

Cognitive behavior therapy (CBT) for children has been shown efficacious, but community access to it is often limited by the lack of trained therapists. This study evaluated a child, CBT-focused, 20-session weekly group supervision seminar with a didactic component which was provided to community mental health practitioners by experienced CBT therapists from an academic center.

METHODS

Twenty-two practitioners from four community mental health agencies completed the training in four groups (one for each agency); one group was trained by videoconference. The authors assessed outcomes immediately after the training and at 6-month follow-up using a mixed-method design including quantitative and qualitative methods to ensure a comprehensive evaluation.

RESULTS

Participants' knowledge on a multiple-choice test of child CBT increased with training, as did their self-reported confidence using CBT and desire to do further child CBT. Therapist age and use of an intake diagnostic screen related to positive outcomes, and participants advocated for more structured training.

CONCLUSION

Child CBT can be successfully taught to community practitioners using this training model, but refinement based on participant feedback and further studies that include direct observation of CBT skills are needed.

Association of attention-deficit/hyperactivity disorder with a candidate region for reading disabilities on chromosome 6p

BACKGROUND

Reading disabilities (RD) and attention-deficit hyperactivity/disorder (ADHD) are two common childhood disorders that co-occur by chance more often than expected. Twin studies and overlapping genetic linkage findings indicate that shared genetic factors partially contribute to this comorbidity. Linkage of ADHD to 6p, an identified RD candidate locus, has previously been reported, suggesting the possibility of a pleiotropic gene at this locus. RD has been previously associated with five genes in the region, particularly DCDC2 and KIAA0319.

METHODS

To test whether these genes also contribute to ADHD, we investigated markers previously associated with RD for association with ADHD and ADHD symptoms in a sample of families with ADHD (n = 264). Markers were located in two subregions, VMP/DCDC2 and KIAA0319/TTRAP.

RESULTS

Across all analyses conducted, strong evidence for association was observed in the VMP/DCDC2 region. Association was equally strong with symptoms of both inattention and hyperactivity/impulsivity, suggesting that this locus contributes to both symptom dimensions. Markers were also tested for association with measures of reading skills (word identification, decoding); however, there was virtually no overlap in the markers associated with ADHD and those associated with reading skills in this sample.

CONCLUSIONS

Overall this study supports a previous linkage study of ADHD indicating a risk gene for ADHD on 6p and points to VMP or DCDC2 as the most likely candidates.

Association of ADHD and the Protogenin gene in the chromosome 15q21.3 reading disabilities linkage region

Twin studies indicate genetic overlap between symptoms of attention deficit hyperactivity disorder (ADHD) and reading disabilities (RD), and linkage studies identify several chromosomal regions possibly containing common susceptibility genes, including the 15q region. Based on a translocation finding and association to two specific alleles, the candidate gene, DYX1C1, has been proposed as the susceptibility gene for RD in 15q. Previously, we tested markers in DYX1C1 for association with ADHD. Although we identified association for haplotypes across the gene, we were unable to replicate the association to the specific alleles reported. Thus, the risk alleles for ADHD are yet to be identified. The susceptibility alleles may be in a remote regulatory element, or DYX1C1 may not be the risk gene. To continue study of 15q, we tested a coding region change in DYX1C1, followed by markers across the gene Protogenin (PRTG) in 253 ADHD nuclear families. PRTG was chosen based on its location and because it is closely related to DCC and Neogenin, two genes known to guide migratory cells and axons during development. The markers in DYX1C1 were not associated to ADHD when analyzed individually; however, six markers in PRTG showed significant association with ADHD as a categorical trait (P = 0.025-0.005). Haplotypes in both genes showed evidence for association. We identified association with ADHD symptoms measured as quantitative traits in PRTG, but no evidence for association with two key components of reading, word identification and decoding was observed. These findings, while preliminary, identify association of ADHD to a gene that potentially plays a role in cell migration and axon growth.

Developing a risk-model of time to first-relapse for children and adolescents with a psychotic disorder

Individuals treated for psychotic disorders and mood disorders with psychotic features have a high likelihood of relapse across the life course. This study examines the relapse rate and its associated predictors for children and adolescents experiencing a first-episode and develops a statistical risk-model for prediction of time to first-relapse. A multiyear, retrospective cohort design was used to track youth, under the age of 18 years, who experienced a first-episode of psychosis, and were admitted to 1 of 6 inpatient hospital psychiatric units (N = 87). Participants were followed for at least 2 years (M = 3.9, SD = 1.3) using survival analysis. Approximately 60% of subjects experienced relapse requiring hospital readmission by the end of follow-up, with 33% readmitted within the first year and 44% within 2 years. Median survival time was 34 months. Cox proportional hazards regression identified 4 key risk factors for relapse: medication nonadherence, female gender, receiving clinical treatment, and a decline in social support before first admission.

Association study for genes at chromosome 5p13-q11 in attention deficit hyperactivity disorder

Linkage of attention deficit hyperactivity disorder (ADHD) to the short arm-centromeric region of chromosome 5 has been reported in multiple studies. The overlapping region (5p13-q11) contains a number of strong candidate genes for ADHD, based on their role in brain function or neurodevelopment. The aim of this study was to investigate some of the top candidates among these genes in relation to ADHD in a sample of 245 nuclear families from the Toronto area. We investigated the genes for the glial cell-derived neurotropic factor (GDNF), the fibroblast growth factor 10 (FGF10), islet-1 (ISL1), the hyperpolarized potassium channel (HCN1) and the integrin alpha 1 (ITGA1). In addition to these genes, we assessed the 3'region of the SLC1A3 gene, a glutamate transporter implicated in ADHD by a previous association study. A total of 36 polymorphisms were selected across the six genes. We performed family-based association and haplotype analyses. ADHD is a dimensional disorder, with symptoms of inattention and hyperactivity-impulsivity therefore, we also conducted quantitative analysis in relation to symptom scores for both dimensions. Single marker and haplotype analyses yielded little evidence of association for any of the genes tested in this study. Moreover, we were unable to replicate the positive association findings reported for SLC1A3. Our results suggest that these six genes are unlikely to be susceptibility genes in the chromosome 5p13-q11 region and other genes should now be considered for priority study.

Mathematical learning disorder in school-age children with attention-deficit hyperactivity disorder

OBJECTIVES

To explore the prevalence of mathematics disorder (MD) relative to reading disorders (RD) in school-age children with attention-deficit hyperactivity disorder (ADHD) and examine the effects of age, sex, cooccurring conduct disorder (CD), and ADHD subtype on this comorbidity.

METHODS

Participants were school-age children (n = 476) with confirmed DSM-IV diagnosis of ADHD. The assessment included semistructured parent and teacher interviews and standardized measures of intelligence, academic attainment, and language abilities. Based on the presence or absence of concurrent learning disorders, we compared the emerging 4 groups: ADHD-only, ADHD + MD, ADHD + RD, and ADHD + MD + RD.

RESULTS

Overall prevalence of comorbid ADHD + MD was 18.1%. Age, sex, ADHD subtypes, or comorbid CD did not affect the frequency of MD. Children with concurrent ADHD and either MD or RD attained lower IQ, language, and academic scores than those with ADHD alone. Children with ADHD + MD + RD were more seriously impaired and demonstrated distinct deficits in receptive and expressive language.

CONCLUSION

MDs are relatively common in school-age children with ADHD and are frequently associated with RDs. Children with ADHD + MD + RD are more severely impaired. These deficits simply cannot be explained as consequences of ADHD and might have unique biological underpinnings, with implications for diagnostic classification and therapeutic interventions.

No evidence for genetic association between DARPP-32 (PP1R1B) polymorphisms and attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) has a strong genetic basis, and evidence from human and animal studies suggests that a dopamine system dysfunction plays a role in the disorder pathophysiology. Several genes involved in dopamine neurotransmission have shown replicated genetic association with ADHD. These include the dopamine receptors D4 (DRD4), D5 (DRD5), and the dopamine transporter (DAT1) genes. Recently, evidence has also accumulated in favor of the dopamine receptor D1 gene (DRD1). The dopamine- and cAMP-regulated phosphoprotein of relative molecular mass of 32 kDa (DARPP-32) is a key component of dopamine signaling, acting as a converging point for several neurotransmitter systems influencing dopaminergic neurons and regulating a wide variety of downstream effectors. Here, we tested the DARPP-32 gene, PPP1R1B, for association with ADHD using four polymorphic markers selected across the gene in a sample of 255 ADHD families. We did not detect evidence of association of individual marker alleles and haplotype analysis did not reveal significant association in this sample of families. Moreover, we found no relationship between the same alleles or haplotypes and symptom scores of inattention or hyperactivity/impulsivity in these families using a quantitative approach. In conclusion, albeit a key regulatory role in dopamine signaling, our data do not support a major contribution of the DARPP-32 gene in ADHD.

Cognitive and behavioral effects of multilayer-release methylphenidate in the treatment of children with attention-deficit/hyperactivity disorder

OBJECTIVE

The aim of this study was to compare the pharmacodynamics of a new multilayer-release (MLR) formulation methylphenidate (MPH; Biphentin) with immediate-release (IR) MPH (Ritalin) in a double-blind, cross-over, placebo-controlled study in patients with attention-deficit/hyperactivity disorder (ADHD).

METHOD

Patients were randomized to equivalent doses of MPH as MLR (once per day), IR (twice per day) or placebo. Each treatment was taken for 1 week prior to repeated behavioral and cognitive laboratory evaluations on a single day in each phase of the crossover.

RESULTS

Two girls and 15 boys 6.8-15.3 years old (mean age 11.3 +/- 2.2 years) participated. Both MLR and IR MPH significantly reduced the Stop Signal Reaction Time (p = 0.0001, p = 0.0005), the Errors of Omission on the Continuous Performance Task (p = 0.0039, p = 0.0001), the IOWA-Conners Inattention/Overactivity Index (p = 0.0001, p = 0.0001), and increased the Clinical Global Impressions (CGI) Efficacy Index (p = 0.0001, p = 0.0017) and reduced the CGI Global Improvement Index (p = 0.0001, p = 0.0006) compared to placebo. Mild adverse events were experienced by 4, 6, and 3 patients on placebo, IR, and MLR MPH, respectively.

CONCLUSIONS

MLR MPH given once daily produces equivalent improvements in behavioral and cognitive measures, and has a duration of effect at least as long as that of IR MPH given twice daily.

Investigation of the G protein subunit Galphaolf gene (GNAL) in attention deficit/hyperactivity disorder

The dopamine system plays an important role in the regulation of attention and motor behavior, subsequently, several dopamine-related genes have been associated with Attention Deficit/Hyperactivity Disorder (ADHD). Among them are the dopamine receptors D1 and D5 that mediate adenylyl cyclase activation through coupling with G(s)-like proteins. We thus hypothesized that the G(s)-like subunit Galpha(olf), expressed in D1-rich areas of the brain, contributes to the genetic susceptibility of ADHD. To evaluate the involvement of the Galpha(olf) gene, GNAL, in ADHD, we examined the inheritance pattern of 12 GNAL polymorphisms in 258 nuclear families ascertained through a proband with ADHD (311 affected children) using the transmission/disequilibrium test (TDT). Categorical analysis of individual marker alleles demonstrated biased transmission of one polymorphism in GNAL intron 3 (rs2161961; P=0.011). We also observed significant relationships between rs2161961 and dimensional symptoms of inattention and hyperactivity/impulsivity (P=0.003 and P=0.008). In addition, because of recent evidence of imprinting at the GNAL locus, secondary analyses were split into maternal and paternal transmissions to assess a contribution of parental effects. We found evidence of strong maternal effect, with preferential transmission of maternal alleles for rs2161961A (P=0.005) and rs8098539A (P=0.035). These preliminary findings suggest a possible contribution of GNAL in the susceptibility to ADHD, with possible involvement of parent-of-origin effects.

Predictive validity of DSM-IV and ICD-10 criteria for ADHD and hyperkinetic disorder

BACKGROUND

The goal of this study was to compare the predictive validity of the two main diagnostic schemata for childhood hyperactivity - attention-deficit hyperactivity disorder (ADHD; Diagnostic and Statistical Manual- IV) and hyperkinetic disorder (HKD; International Classification of Diseases- 10th Edition).

METHODS

Diagnostic criteria for ADHD and HKD were used to classify 419 children ages 6 to 16 years referred to a clinic for behavioral problems into one of four groups: HKD, ADHD combined subtype (ADHD-C), ADHD hyperactive-impulsive subtype (ADHD-HI), ADHD inattentive subtype (ADHD-IA). These groups were compared on clinical characteristics including total symptom severity, overall impairment, exposure to psychosocial and neuro-developmental risks, family history of ADHD in first-degree family members, rate and type of comorbidity, intelligence, academic achievement, and on laboratory tests of motor response inhibition and working memory with each other and with normal controls (47).

RESULTS

Of the 419 cases, there were 46 HKD (11.0%), 200 ADHD-C (47.7%), 60 ADHD-HI (14.3%) and 113 ADHD-IA (27.0%) cases. The HKD group had more symptoms and was more impaired on teachers' ratings than were the other groups. The ADHD-C and HKD groups had poorer inhibitory control than the ADHD-IA, ADHD-HI and control groups, and all four clinic groups showed inhibition deficit compared to controls. Groups did not differ in working memory. Compared to controls, the HKD, ADHD-C, ADHD-HI and ADHD-IA groups had higher familial risk of ADHD, greater psychosocial risk exposure, lower intellectual level and poorer academic attainment. However, we observed no differences among the clinic groups in these characteristics.

CONCLUSIONS

Like earlier versions, ICD-10 and DSM-IV continue to delineate diagnostic entities with substantially different prevalence in clinic samples. However, HKD, ADHD-C, ADHD-IA and ADHD-HI groups overlap substantially in terms of important clinical characteristics, although HKD and ADHD-C may be somewhat more severe variants of the condition than ADHD-IA and ADHD-HI.

Association study of the brain-derived neurotropic factor (BDNF) gene in attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a prevalent neurodevelopmental childhood psychiatric disorder. Brain-derived neurotropic factor (BDNF) has been suggested to play a role in the pathogenesis of ADHD and two family-based association studies demonstrated an association of BDNF polymorphisms with ADHD. The aim of the current study was to investigate the BDNF gene for association with ADHD in a large sample of families from Toronto. The transmission of three polymorphisms of the BDNF gene (rs6265, rs11030104, and rs2049046) was examined in 266 nuclear families ascertained through a proband with ADHD (315 affected children) using the transmission/disequilibrium test (TDT). In addition, we conducted quantitative analysis to assess the relationship between these marker alleles and the symptom dimensions of ADHD (inattention and hyperactivity/impulsivity) and cognitive measures of working memory. None of the individual marker alleles showed significant evidence of association with ADHD, dimensional symptom scores, or working memory ability in our sample of ADHD families. There was no significant evidence for biased transmission of individual haplotypes with frequency >10% (global chi2 for these three haplotypes: chi2 = 6.349, df = 3, P = 0.096). One uncommon haplotype (A-G-G; frequency 2.2%) showed a significant association with ADHD in the categorical (chi2 = 5.293, df = 1, P = 0.021) and quantitative analyses (parents' rated inattention: Z = -2.504, P = 0.012; and hyperactivity/impulsivity: Z = -2.651, P = 0.008). These results should be interpreted cautiously, however, because of the low haplotype frequency. In light of the evidence for an involvement of BDNF in ADHD, further analysis of the BDNF gene in ADHD is warranted.

The gene for synapsin III and attention-deficit hyperactivity disorder

OBJECTIVE

Recent studies have implicated the involvement of proteins regulating neurotransmitter release in the etiology of attention deficit hyperactivity disorder. On the basis of the role of synapsin III in the modulation of neurotransmitter release, we tested this gene as a candidate contributing to the genetic susceptibility of attention deficit hyperactivity disorder.

METHOD

In this study, we genotyped five markers across the gene on 177 small, nuclear families consisting of an attention deficit hyperactivity disorder proband, their parents, and 43 affected siblings. We examined the transmission of the alleles at each one of these sites and the haplotypes of the polymorphisms using the transmission disequilibrium test.

RESULT

Our observations did not yield any evidence of biased transmission of the alleles at any polymorphism or haplotype. On the basis of the evidence for synapsins in learning and memory from animal models, we also investigated the relationship of this gene to verbal short-term and working memory as measured by digit span forward and backwards. No evidence was found for an association of this gene to these traits.

CONCLUSION

Our findings with this particular sample do not support the synapsin III locus as a major susceptibility locus contributing to attention deficit hyperactivity disorder.

Association study of the nicotinic acetylcholine receptor alpha4 subunit gene, CHRNA4, in attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is a common childhood-onset psychiatric condition with a strong genetic component. Evidence from pharmacological, clinical and animal studies has suggested that the nicotinic system could be involved in the disorder. Previous studies have implicated the nicotinic acetylcholine receptor alpha4 subunit gene, CHRNA4, in ADHD. Particularly, a polymorphism in the exon 2-intron 2 junction of CHRNA4 has been associated with severe inattention defined by latent class analysis. In the current study, we used the transmission disequilibrium test (TDT) to investigate four polymorphisms encompassing this region of CHRNA4 for association with ADHD in a sample of 264 nuclear families from Toronto. No significant evidence of biased transmission was observed for any of the marker alleles for ADHD defined as a categorical trait (all subtypes included), although one haplotype showed marginal evidence of under-transmission. No association was found with the ADHD predominantly inattentive subtype or with symptom dimension scores of inattention. On the contrary, nominally significant evidence of association of individual markers was obtained for the ADHD combined subtype and with teacher-rated hyperactivity-impulsivity scores, with the same haplotype being under-transmitted. Based on our results and others, CHRNA4 may be involved in ADHD; however, its role in ADHD symptomatology remains to be clarified.

Comparison of the predictive validity of hyperkinetic disorder and attention deficit hyperactivity disorder

INTRODUCTION

We compared the predictive validity of attention deficit hyperactivity disorder (ADHD; Diagnostic and Statistical Manual - IV Edition) and hyperkinetic disorder (HKD; International Classification of Diseases - 10th Edition) while controlling for the presence of comorbid psychopathology.

METHOD

ADHD and HKD criteria were used to classify 804 clinic-referred children ages 6 to 16 years into one of four non-overlapping groups: HKD, ADHD combined subtype (ADHD-C), ADHD hyper-active-impulsive subtype (ADHD-HI), ADHD inattentive subtype (ADHD-IA). Groups were compared with each other and with normal controls (67) while controlling for age and intelligence on a range of criteria both before and after excluding cases with comorbidity.

RESULTS

Of the 804 clinic participants, 72 (8.9 %) met criteria for ICD-10 HKD, 353 (43.9 %) for ADHD-C, 142 (17.7 %) for ADHD-HI and 237 (29.5 %) for ADHD-IA. There were no differences among the four clinic groups in rate of comorbidity, neuro-developmental or psychosocial risk indices, inter-parental or parent-child discord, family history of ADHD, working memory, and academic or intelligence test scores, but all clinic groups differed from normal controls. By contrast, total number of symptoms, teacher-rated impairment and inhibitory control deficit were greatest in HKD and least in ADHD-C, ADHD-HI, ADHD-IA in that order. Results of the comparisons were essentially unchanged after excluding cases (75%) with a comorbid condition.

CONCLUSIONS

HKD, ADHD-C, ADHD-HI and ADHD-IA had approximately equivalent predictive validity even when comorbidity was taken into account.

Restraint and Cancellation: Multiple Inhibition Deficits in Attention Deficit Hyperactivity Disorder

We used variations of the stop signal task to study two components of motor response inhibition-the ability to withhold a strong response tendency (restraint) and the ability to cancel an ongoing action (cancellation)-in children with a diagnosis of attention deficit hyperactivity disorder (ADHD) and in non-ADHD controls of similar age (ages 7-14 years). The goal was to determine if restraint and cancellation were related and if both were deficient in ADHD. The stop signal task involved a choice reaction time task (go task) which required a rapid response. The demand for inhibitory control was invoked through the presentation of a stop signal on a subset of go trials which required that the ongoing response be suspended. The stop signal was presented either concurrently with the go signal (restraint version) or after a variable delay (cancellation version). In Study 1, we compared ADHD and control children on the cancellation version of the stop task; in Study 2, we compared ADHD and controls on the restraint version. In Study 3, a subset of ADHD and control participants completed both tasks so that we could examine convergence of these dimensions of inhibition. Compared to control participants, ADHD participants showed a deficit both in the ability to cancel and to restrain a speeded motor response. Performance on the restraint version was significantly correlated with performance on the cancellation version in controls, but not in ADHD participants. We conclude that ADHD is associated with deficits in both restraint and cancellation subcomponents of inhibition.

The serotonin receptor HTR1B: gene polymorphisms in attention deficit hyperactivity disorder

Serotonin plays an essential role in cognition, locomotor activity, and the regulation of sleep, pain, mood, and aggression. Polymorphisms of the HTR1B gene have been implicated in a variety of psychiatric disorders including attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD). The objectives of this study were to: (i) expand our original investigation of the relationship between the HTR1B receptor gene and attention deficit/hyperactivity and; (ii) to investigate a possible association of obsessive behaviors/perfectionism and the HTR1B gene in a sample of 203 families with an ADHD proband. Six single nucleotide polymorphisms (SNPs) of the HTR1B receptor gene were genotyped using standard methods. Evidence for an association between the HTR1B gene and ADHD as a qualitative diagnosis, or the inattentive and hyperactive-impulsive quantitative traits was not supported by either TDT single marker analysis or haplotype analysis. In addition we did not find evidence to suggest an association between HTR1B and perfectionism in this sample of ADHD families.

Association of the glutamate receptor subunit gene GRIN2B with attention-deficit/hyperactivity disorder

The glutamatergic signaling pathway represents an ideal candidate susceptibility system for attention-deficit/hyperactivity disorder (ADHD). Disruption of specific N-methyl-D-aspartate-type glutamate receptor subunit genes (GRIN1, 2A-D) in mice leads to significant alterations in cognitive and/or locomotor behavior including impairments in latent learning, spatial memory tasks and hyperactivity. Here, we tested for association of GRIN2B variants with ADHD, by genotyping nine single nucleotide polymorphisms (SNPs) in 205 nuclear families identified through probands with ADHD. Transmission of alleles from heterozygous parents to affected offspring was examined using the transmission/disequilibrium test. Quantitative trait analyses for the ADHD symptom dimensions [inattentive (IA) and hyperactive/impulsive (HI)] and cognitive measures of verbal working memory and verbal short-term memory were performed using the fbat program. Three SNPs showed significantly biased transmission (P < 0.05), with the strongest evidence of association found for rs2,284,411 (chi(2)= 7.903, 1 degree of freedom, P= 0.005). Quantitative trait analyses showed associations of these markers with both the IA and the HI symptom dimensions of ADHD but not with the cognitive measures of verbal short-term memory or verbal working memory. Our data suggest an association between variations in the GRIN2B subunit gene and ADHD as measured categorically or as a quantitatively distributed trait.

Gene for the serotonin transporter and ADHD: no association with two functional polymorphisms

Evidence from both human and animal studies implicates the serotonergic system in the development of attention-deficit hyperactivity disorder (ADHD) including positive association studies for several key serotonergic genes. The serotonin transporter (HTT) regulates the availability of serotonin by reuptake of the neurotransmitter from the synaptic cleft. Several studies have reported an association of this gene to ADHD, specifically the long variant of a common insertion/deletion polymorphism located in the promoter of this gene that results in increased transcription and higher HTT expression. An additional study found no evidence for an association with this polymorphism. Recently, an A/G single nucleotide polymorphism (SNP) was found within the promoter polymorphism with functional studies indicating that the long variant containing the G allele at this site behaves like the short variant. This previously unidentified functional change may have confounded earlier association studies. We investigated the relationship of several variants to ADHD: the promoter polymorphisms, SNP in the 3' untranslated region (3'UTR) with a reported association to ADHD and a rare, non-synonymous coding SNP. These polymorphisms were genotyped in 209 ADHD families identified through an affected proband. We did not find evidence for an association of these polymorphisms, or haplotypes of these polymorphisms, to ADHD in this sample.

A methodology for conducting retrospective chart review research in child and adolescent psychiatry

INTRODUCTION

Retrospective research has become largely undervalued and underutilized in child and adolescent psychiatry with the increasing singular focus on randomized control trials, despite the wealth of clinically relevant data available in historical medical records. In this paper a systematic and scientific approach to chart review research methodology for psychiatry is described.

METHOD

Informed by available literature, a methodological stepwise approach for retrospective chart review was developed.

RESULTS

A nine step method aimed at maximizing benefits and minimizing limitations is discussed.

CONCLUSIONS

Retrospective chart review is an important methodology with distinct advantages and has the potential to provide psychiatry with valuable research opportunities. This method of study should not be lost in the field of psychiatry.

Stimulant treatment over 5 years: effects on growth

OBJECTIVE

Long-term effects of psychostimulants on growth in height and in weight are investigated in children with attention-deficit/hyperactivity disorder.

METHOD

Participants were 79 children, 6 to 12 years of age, with attention-deficit/hyperactivity disorder, who were followed annually for up to 5 years, between the years 1993 and 1994 and 1998 and 1999. Annual height and weight measurements were standardized by age and gender using the 2000 Centers for Disease Control and Prevention Growth Charts for the United States and reported as z scores. For children taking stimulants throughout the previous school year, dose potency was standardized to methylphenidate in milligrams per kilogram per day. We used hierarchical linear modeling to investigate the influence of dose and duration of stimulant treatment on the rate of growth in height and weight.

RESULTS

Controlling for time since initiation of treatment, daily dose of stimulant medication was negatively associated with z scores for height (beta = -.11, SE = 0.03, p <.01) and for weight (beta = -.29, SE = 0.04, p <.01). Estimates based on the statistical model suggest that children receiving > or = 1.5 mg/kg/day methylphenidate will show diminished weight gain after 1 year; those receiving > or = 2.5 mg/kg/day methylphenidate will show diminished gains in height after 4 years.

CONCLUSION

Long-term use of high doses of stimulants during a period of 1 to 5 years is likely to have measurable effects on the rate of growth in school-age children with attention-deficit/hyperactivity disorder.

The parent interview for child symptoms: a situation-specific clinical research interview for attention-deficit hyperactivity and related disorders

OBJECTIVE

To describe the properties of a semistructured research interview of parents designed to evaluate attention-deficit hyperactivity disorder (ADHD) and related psychopathology.

METHOD

We examined interrater reliability in 48 videotaped interviews randomly selected from a large clinic sample. We examined convergence of the Parent Interview for Child Symptoms (PICS) and Conners' Parent Rating Scale (CPRS) scores in 594 clinic-referred cases and 26 control subjects, comparing the groups generated by cross-tabulation on measures of intelligence, academic achievement, and inhibitory control.

RESULTS

Intraclass correlation coefficients for symptom scores of ADHD, oppositional defiant disorder (ODD), and conduct disorder (CD) were excellent. We found good reliability for diagnoses of ADHD (e = 0.73) and CD (kappa = 0.73) and excellent reliability for the diagnosis of ODD (kappa = 0.80). Two-thirds of cases were classified similarly on the PICS and the CPRS. Greater impairment in inhibitory control was observed in cases identified as ADHD by the PICS, compared with those identified by the CPRS-ADHD index.

CONCLUSIONS

The PICS displays good reliability and validity, indicating that a balance between clinical applicability and reliability can be achieved in the development of clinical research instruments.

Association of the calcyon gene (DRD1IP) with attention deficit/hyperactivity disorder

Attention deficit/hyperactivity disorder (ADHD) is a childhood-onset disorder characterized by marked inattention, hyperactivity and impulsivity. The dopaminergic system has been hypothesized to be involved in the development of ADHD. Positive associations have been found for the dopamine receptors D1 and D5 genes, suggesting that other genes involved in D1/D5 signalling may also contribute to ADHD. In this study, we tested the calcyon gene (DRD1IP), which encodes a brain-specific D1-interacting protein involved in D1/D5 receptors calcium signalling, for association with ADHD. The inheritance of nine polymorphisms in the calcyon gene was examined in a sample of 215 nuclear families, with 260 affected children, using the transmission/disequilibrium test. The most common haplotype, designated C1, demonstrated significant evidence for excess transmission. Quantitative trait analyses of this haplotype showed significant relationships with both the inattentive (parent's rating, P=0.006; teacher's rating, P=0.003) and hyperactive/impulsive (parent's rating, P=0.004) dimensions of the disorder. Two of the nine marker alleles included in haplotype C1, rs4838721A located approximately 10 kb 5' of the gene and rs2275723C located 10 bp upstream of the exon 5 acceptor splice site, also showed significant evidence for association when analysed individually. As these two variants are not predicted to alter calcyon function, we screened the gene exons by sequencing. No variation in the coding region was identified, suggesting that a causal variant allele resides elsewhere in a regulatory sequence of the gene. These findings support the proposed involvement of the calcyon gene in ADHD and implicate haplotype C1 as containing a risk allele.

Sequence variation in the 3'-untranslated region of the dopamine transporter gene and attention-deficit hyperactivity disorder (ADHD)

The dopamine transporter gene (DAT1) has been reported to be associated with attention-deficit hyperactivity disorder (ADHD) in a number of studies [Cook et al. (1995): Am J Human Genet 56(4):9993-998; Gill et al. (1997): Mol Psychiatry 2(4):311-313; Waldman et al. (1998): Am J Human Genet 63(6):1767-1776; Barr et al. (2001): Biol Psychiatry 49(4):333-339; Curran et al. (2001): Mol Psychiatry 6(4):425-428; Chen et al. (2003): Mol Psychiatry 8(4):393-396]. Specifically, the 10-repeat allele of the 40-bp variable number of tandem repeats (VNTR) polymorphism located in the 3' untranslated region (UTR) of the gene has been found to be associated with ADHD. There is evidence from in vitro studies indicating that variability in the repeat number, and sequence variation in the 3'-UTR of the DAT1 gene may influence the level of the dopamine transporter protein [Fuke et al. (2001): Pharmacogenomics J 1(2):152-156; Miller and Madras (2002): Mol Psychiatry 7(1):44-55]. In this study, we investigated whether DNA variation in the DAT1 3'UTR contributed to ADHD by genotyping DNA variants around the VNTR region in a sample of 178 ADHD families. These included a MspI polymorphism (rs27072), a DraI DNA change (T/C) reported to influence DAT1 expression levels, and a BstUI polymorphism (rs3863145) in addition to the VNTR. We also screened the VNTR region by direct resequencing to determine if there was sequence variation within the repeat units that could account for the association. Our results indicate that DAT1 is associated with ADHD in our sample but not with alleles of the VNTR polymorphism. We did not find any variation in the sequence for either the 10- or 9-repeat alleles in the probands screened nor did we observe the reported DraI (T/C) variation. Our results therefore refute the possibility of the reported DraI variation or alleles of the VNTR as the functional variants contributing to the disorder.

The SNAP25 gene as a susceptibility gene contributing to attention-deficit hyperactivity disorder

The synaptosomal-associated protein of 25 kDa gene (SNAP25) has been suggested as a genetic susceptibility factor in attention-deficit hyperactivity disorder (ADHD) based on the mouse strain coloboma. This strain is hemizygous for the SNAP25 gene and displays hyperactivity that responds to dextroamphetamine, but not to methylphenidate. Previously, we reported association of SNAP25 and ADHD using two polymorphisms. To further investigate this gene, we screened the exons for DNA variation and genotyped ten additional polymorphisms in an expanded sample of families from Toronto and a second sample of families collected in Irvine, CA. Significant results were observed in the Toronto sample for four markers, although not in the Irvine sample. The paper discusses the possible influence of the selection criteria on these differential results. The Irvine sample selected subjects that met the DSM-IV combined subtype diagnosis, whereas the Toronto sample included all subtypes. Analysis of the DSM-IV subtypes in the Toronto sample indicated that the differential results were not attributable to ADHD subtype. Differences in ethnicity, differential medication response, and other clinical characteristics of the samples cannot be ruled out at this time. Quantitative analysis of the dimensions of hyperactivity/impulsivity and inattention in the Toronto sample found that both behavioral traits were associated with SNAP25. Our findings continue to support SNAP25 in the susceptibility to ADHD.

Inhibition of motor responses in siblings concordant and discordant for attention deficit hyperactivity disorder

OBJECTIVE

The authors sought to determine whether nonaffected siblings of ADHD probands have a motor response inhibition deficit and to assess concordance for this inhibition deficit in ADHD-concordant and ADHD-discordant sibling pairs.

METHOD

ADHD-concordant pairs (21 probands and their affected siblings), ADHD-discordant pairs (18 probands and their nonaffected siblings), and a group of unrelated, demographically balanced, healthy individuals (N=24) were compared on measures of response inhibition, ADHD behavior, impairment, and environmental risk.

RESULTS

Concordant-pair probands, their affected siblings, and discordant-pair probands exhibited inhibitory control impairment relative to healthy comparison subjects. The performance of nonaffected siblings was intermediate between that of ADHD children and the healthy comparison subjects. Group differences persisted after age was controlled, and performance was not correlated with the number of ADHD symptoms. In ADHD-concordant sibling pairs, there was a significant relationship between proband and sibling inhibition deficit. In ADHD-discordant sibling pairs, inhibition deficit was evident in half of the nonaffected siblings of probands with an inhibition deficit. Groups did not differ in exposure to environmental risks.

CONCLUSIONS

Impaired inhibitory control aggregates in the family members of individuals with ADHD and may serve as an indicator of genetic vulnerability to the disorder.

Attention-deficit hyperactivity disorder with and without obsessive-compulsive behaviours: clinical characteristics, cognitive assessment, and risk factors

OBJECTIVES

To determine the prevalence of obsessive--compulsive behaviours (OCB) in a clinical sample of children with attention-deficit hyperactivity disorder (ADHD) and to compare ADHD children (with and without OCB) with respect to clinical and cognitive characteristics and risk factors.

METHOD

We compared ADHD children (n = 134) with and without OCB, and we compared all ADHD children with a group of normal control subjects (n = 26) on various clinical, cognitive, and inhibitory control measures; neurobiological and psychosocial risk factors; and family histories of psychiatric illness.

RESULTS

Clinically significant OCB was identified in 11.2% (15/134) of children with ADHD. Comorbid OCB was associated with significantly increased perfectionism, improved teacher ratings of inattention, and a decreased likelihood of having a first-degree relative with ADHD. Comorbid ADHD and OCB may also be associated with increased oppositional behaviour at home and better inhibitory control, though these differences were not statistically significant.

CONCLUSIONS

Comorbid OCB is common in clinically referred children with ADHD and is associated with increased impairment relative to ADHD alone. Further, children with ADHD and OCB may develop symptoms as the result of different genetic and environmental risk factors, compared with children with ADHD only.

Replication test for association of the IL-1 receptor antagonist gene, IL1RN, with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) has a strong genetic basis, and aberrant brain dopaminergic and noradrenergic activity is implicated in its etiology. Interleukin-1 (IL-1), its antagonist, IL-1Ra, and IL-1 receptors are all present in the brain, and IL-1 has been shown to influence both dopaminergic and noradrenergic function. Recently, Segman et al. [1] tested the IL-1Ra gene, IL1RN, as a candidate for involvement in ADHD. Using the transmission/disequilibrium test (TDT) to examine 77 nuclear ADHD families for the inheritance of alleles of an intronic 86-bp VNTR polymorphism, they found significant evidence for biased transmission of the 4-repeat allele (p=0.04) and non-transmission of the 2-repeat allele (p=0.03). Here, we sought to replicate this in an independent sample of families. In contrast to the previous findings, our analysis of 178 ADHD families showed no evidence for biased transmission of these alleles (p=0.81 and p=1.00, respectively). Our lack of evidence for association of this IL1RN polymorphism with ADHD, based on a much larger sample of families, suggests that the original finding may have been a spurious (i.e. false-positive) result. These findings highlight the need for further investigations of this marker, in additional independent ADHD samples, in the future.

Evidence for an Error Monitoring Deficit in Attention Deficit Hyperactivity Disorder

We studied error monitoring in ADHD and control children in a task requiring inhibition of a motor response. The extent of slowing following successful (stopped) and failed (nonstopped) inhibition was compared across groups. We also measured the time required to inhibit a response (stop signal reaction time, SSRT). Compared to controls, ADHD participants slowed less following nonstopped responses. Slowing did not vary with comorbid reading, oppositional, conduct or anxiety disorder, sex or ADHD subtype. Slowing after nonstopped responses was marginally, although significantly correlated with total ADHD symptoms and with age. ADHD participants had significantly longer SSRT than controls, but SSRT was not significantly correlated with slowing. The apparent deficit in error monitoring in ADHD and its independence from the inhibition deficit observed in ADHD has implications for executive control models of ADHD, performance problems associated with the disorder and for component theories of executive control.

Glutamate receptor, ionotropic, N-methyl D-aspartate 2A (GRIN2A) gene as a positional candidate for attention-deficit/hyperactivity disorder in the 16p13 region

The glutamate system may be involved in the development of attention-deficit/hyperactivity disorder (ADHD) based on animal models and the role of N-methyl-D-aspartate receptors (NMDAR) in cognition and motor processes. A follow-up study of the first genome scan for ADHD identified significant evidence for linkage to the 16p13 region. The glutamate receptor, ionotropic, N-methyl D-aspartate 2A (GRIN2A) gene that encodes the 2A subunit of the NMDA receptor, resides in this region and a recent study has reported an association between this gene and ADHD. We tested for linkage between the alleles and haplotypes of four polymorphisms at the GRIN2A locus and ADHD in our sample of 183 nuclear families with 229 affected children. In contrast to previous findings, we did not identify any evidence for a relationship of these markers and ADHD. Owing to the role of GRIN2A in aspects of cognition, we investigated the relationship of this gene to the cognitive phenotypes of inhibitory control, verbal short-term memory and verbal working memory. There was no significant evidence of linkage between GRIN2A and these phenotypes. While the results were not significant in our sample, the previous association finding suggests that further study of this gene is warranted.

Linkage of the dopamine receptor D1 gene to attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) has a strong genetic basis, and evidence from human and animal studies suggests the dopamine receptor D1 gene, DRD1, to be a good candidate for involvement. Here, we tested for linkage of DRD1 to ADHD by examining the inheritance of four biallelic DRD1 polymorphisms [D1P.5 (-1251HaeIII), D1P.6 (-800HaeIII), D1.1 (-48DdeI) and D1.7 (+1403Bsp1286I)] in a sample of 156 ADHD families. Owing to linkage disequilibrium between alleles at the four markers, only three haplotypes are common in our sample. Using the transmission/disequilibrium test (TDT), we observed a strong bias for transmission of Haplotype 3 (1.1.1.2) from heterozygous parents to their affected children (P=0.008). Furthermore, using quantitative trait TDT analyses, we found significant and positive relationships between Haplotype 3 transmission and the inattentive symptoms, but not the hyperactive/impulsive symptoms, of ADHD. These findings support the proposed involvement of DRD1 in ADHD, and implicate Haplotype 3, in particular, as containing a potential risk factor for the inattentive symptom dimension of the disorder. Since none of the four marker alleles comprising Haplotype 3 is predicted to alter DRD1 function, we hypothesize that a functional DRD1 variant, conferring susceptibility to ADHD, is on this haplotype. To search for such a variant we screened the DRD1 coding region, by sequencing, focusing on the children who showed preferential transmission of Haplotype 3. DNA from 41 children was analysed, and no sequence variations were identified, indicating that the putative DRD1 risk variant for ADHD resides outside of the coding region of the gene.