A controlled family study of attention-deficit/hyperactivity disorder and Tourette's disorder

Developing a phenotype risk score for tic disorders in a large, clinical biobank

Tics are a common feature of early-onset neurodevelopmental disorders, characterized by involuntary and repetitive movements or sounds. Despite affecting up to 2% of children and having a genetic contribution, the underlying causes remain poorly understood. In this study, we leverage dense phenotype information to identify features (i.e., symptoms and comorbid diagnoses) of tic disorders within the context of a clinical biobank. Using de-identified electronic health records (EHRs), we identified individuals with tic disorder diagnosis codes. We performed a phenome-wide association study (PheWAS) to identify the EHR features enriched in tic cases versus controls (n = 1406 and 7030; respectively) and found highly comorbid neuropsychiatric phenotypes, including: obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, autism spectrum disorder, and anxiety (p < 7.396 × 10-5). These features (among others) were then used to generate a phenotype risk score (PheRS) for tic disorder, which was applied across an independent set of 90,051 individuals. A gold standard set of tic disorder cases identified by an EHR algorithm and confirmed by clinician chart review was then used to validate the tic disorder PheRS; the tic disorder PheRS was significantly higher among clinician-validated tic cases versus non-cases (p = 4.787 × 10-151; β = 1.68; SE = 0.06). Our findings provide support for the use of large-scale medical databases to better understand phenotypically complex and underdiagnosed conditions, such as tic disorders.

Developing a Phenotype Risk Score for Tic Disorders in a Large, Clinical Biobank

Importance

Tics are a common feature of early-onset neurodevelopmental disorders, characterized by involuntary and repetitive movements or sounds. Despite affecting up to 2% of young children and having a genetic contribution, the underlying causes remain poorly understood, likely due to the complex phenotypic and genetic heterogeneity among affected individuals.

Objective

In this study, we leverage dense phenotype information from electronic health records to identify the disease features associated with tic disorders within the context of a clinical biobank. These disease features are then used to generate a phenotype risk score for tic disorder.

Design

Using de-identified electronic health records from a tertiary care center, we extracted individuals with tic disorder diagnosis codes. We performed a phenome-wide association study to identify the features enriched in tic cases versus controls (N=1,406 and 7,030; respectively). These disease features were then used to generate a phenotype risk score for tic disorder, which was applied across an independent set of 90,051 individuals. A previously curated set of tic disorder cases from an electronic health record algorithm followed by clinician chart review was used to validate the tic disorder phenotype risk score.

Main Outcomes and Measures

Phenotypic patterns associated with a tic disorder diagnosis in the electronic health record.

Results

Our tic disorder phenome-wide association study revealed 69 significantly associated phenotypes, predominantly neuropsychiatric conditions, including obsessive compulsive disorder, attention-deficit hyperactivity disorder, autism, and anxiety. The phenotype risk score constructed from these 69 phenotypes in an independent population was significantly higher among clinician-validated tic cases versus non-cases.

Conclusions and Relevance

Our findings provide support for the use of large-scale medical databases to better understand phenotypically complex diseases, such as tic disorders. The tic disorder phenotype risk score provides a quantitative measure of disease risk that can be leveraged for the assignment of individuals in case-control studies or for additional downstream analyses.

Co-Occurrence of Tic Disorders and Attention-Deficit/Hyperactivity Disorder-Does It Reflect a Common Neurobiological Background?

BACKGROUND

The co-existence of tic disorders and attention-deficit/hyperactivity disorder (TD + ADHD) has proven to be highly important in daily clinical practice. The factor ADHD is not only associated with further comorbidities, but also has a long-term negative psychosocial effect, while the factor TD is usually less disturbing for the major part of the patients. It remains unclear how far this is related to a different neurobiological background of the associated disorders or whether TD + ADHD reflects a common one.

OBJECTIVE

This review provides an update on the neurobiological background of TD + ADHD in order to better understand and treat this clinical problem, while clarifying whether an additive model of TD + ADHD holds true and should be used as a basis for further clinical recommendations.

METHOD

A comprehensive research of the literature was conducted and analyzed, including existing clinical guidelines for both TD and ADHD. Besides genetical and environmental risk factors, brain structure and functions, neurophysiological processes and neurotransmitter systems were reviewed.

RESULTS

Only a limited number of empirical studies on the neurobiological background of TD and ADHD have taken the peculiarity of co-existing TD + ADHD into consideration, and even less studies have used a 2 × 2 factorial design in order to disentangle the impact/effects of the factors of TD versus those of ADHD. Nevertheless, the assumption that TD + ADHD can best be seen as an additive model at all levels of investigation was strengthened, although some overlap of more general, disorder non-specific aspects seem to exist.

CONCLUSION

Beyond stress-related transdiagnostic aspects, separate specific disturbances in certain neuronal circuits may lead to disorder-related symptoms inducing TD + ADHD in an additive way. Hence, within a classificatory categorical framework, the dimensional aspects of multilevel diagnostic-profiling seem to be a helpful precondition for personalized decisions on counselling and disorder-specific treatment in TD + ADHD.

Effectiveness of 'Tackle Your Tics', a brief, intensive group-based exposure therapy programme for children with tic disorders: study protocol of a randomised controlled trial

INTRODUCTION

This paper outlines the study protocol for the Dutch Tackle Your Tics study in youth with tic disorders. Tourette syndrome and chronic tic disorders are prevalent neurodevelopmental disorders, placing considerable burden on youth and their families. Behavioural treatment is the first-line, evidence-based intervention for tic disorders, but tic reduction and availability remain relatively low. Patient associations stress the need for more accessible high-quality treatments, also focusing on improving quality of life. Therefore, the brief, intensive group-based treatment Tackle Your Tics was developed.

METHODS AND ANALYSIS

Tackle Your Tics is a 4-day intensive and comprehensive group-based intervention for children and adolescents (9-17 years) with Tourette syndrome or a chronic tic disorder. The programme encompasses exposure and response prevention treatment and additional supporting components (coping strategies, relaxation exercises and parent support). To study the effectiveness of Tackle Your Tics and identify predictors/moderators at baseline, a single-blinded randomised controlled trial (n=104) is conducted, comparing Tackle Your Tics (n=52) with a waiting list condition lasting 3 months (n=52). Assessments are performed at similar time points for both groups: at baseline, after 4 weeks, and at 3 and 6 months of follow-up, on tic severity, quality of life and other psychosocial variables.

ETHICS AND DISSEMINATION

Ethics approval has been obtained from the medical ethical committee of the Amsterdam Medical Centre (METC nr NL66340.018.18, v3 June 2020). Findings will be presented on national and international conferences, peer-reviewed scientific journals, patient organisation meetings and public media. Patient representatives are fully integrated as part of the research team. If Tackle Your Tics proves to be effective, it can expand evidence-based treatment possibilities for children and adolescents with tic disorders. Identifying the psychosocial predictors/moderators for the effectiveness of this intervention can provide personalised treatment advice in the future.

TRIAL REGISTRATION NUMBER

NL8052.

Concordance and comorbidities among monozygotic twins with tic disorders

Gilles de la Tourette Syndrome (GTS) is a multifactorial neurodevelopmental disorder characterized by tics and multiple comorbidities. The pathophysiology is not yet fully understood, but both environmental and genetic risk factors seem to be involved. Twin studies provide important knowledge on genetic factors. We assessed the concordance of GTS and chronic tic disorders (CTD) in monozygotic (MZ) twins, and examined tic severity, symptoms of obsessive-compulsive disorder (OCD), attention deficit/hyperactivity disorder and autism spectrum disorder. Twin pairs, where at least one twin was diagnosed with any tic disorder, were identified through Danish Twin Registry, Psychiatric Central Registry, Danish National Patient Registry and National Tourette Clinic, Copenhagen University Hospital, Herlev. Zygosity was tested with single-nucleotide polymorphism (SNP) genotyping and clinical assessment was done with validated tools. 14 MZ twin pairs were included: five were discordant. Seven twin pairs were concordant for GTS, and for two pairs one twin had GTS and the other CTD. Among the twins with CTD or GTS, 50% had at least one comorbidity, which is higher than in background populations. The GTS + OCD-phenotype was significantly more frequent among GTS-concordant than among discordant twins. No statistically significant differences were found between the GTS-concordant and discordant twin pairs regarding tic severity or comorbidities. Thorough clinical assessment and SNP-based genotyping are important when conducting clinical twin studies. We found high concordance of GTS and CTD, which supports the notion that both disorders have common genetic risk factors. Further studies with larger cohorts including dizygotic twins are warranted for more conclusive results.

A Comprehensive Review of Tic Disorders in Children

Tics are characterized by sudden, rapid, recurrent, nonrhythmic movement or vocalization, and are the most common movement disorders in children. Their onset is usually in childhood and tics often will diminish within one year. However, some of the tics can persist and cause various problems such as social embarrassment, physical discomfort, or emotional impairments, which could interfere with daily activities and school performance. Furthermore, tic disorders are frequently associated with comorbid neuropsychiatric symptoms, which can become more problematic than tic symptoms. Unfortunately, misunderstanding and misconceptions of tic disorders still exist among the general population. Understanding tic disorders and their comorbidities is important to deliver appropriate care to patients with tics. Several studies have been conducted to elucidate the clinical course, epidemiology, and pathophysiology of tics, but they are still not well understood. This article aims to provide an overview about tics and tic disorders, and recent findings on tic disorders including history, definition, diagnosis, epidemiology, etiology, diagnostic approach, comorbidities, treatment and management, and differential diagnosis.

Tics and Tourette Syndrome

PURPOSE OF REVIEW

The purpose of this article is to present current information on the phenomenology, epidemiology, comorbidities, and pathophysiology of tic disorders and discuss therapy options. It is hoped that a greater understanding of each of these components will provide clinicians with the necessary information to deliver thoughtful and optimal care to affected individuals.

RECENT FINDINGS

Recent advances include the finding that Tourette syndrome is likely due to a combination of several different genes, both low-effect and larger-effect variants, plus environmental factors. Pathophysiologically, increasing evidence supports involvement of the cortical-basal ganglia-thalamocortical circuit; however, the primary location and neurotransmitter remain controversial. Behavioral therapy is first-line treatment, and pharmacotherapy is based on tic severity. Several newer therapeutic agents are under investigation (eg, valbenazine, deutetrabenazine, cannabinoids), and deep brain stimulation is a promising therapy.

SUMMARY

Tics, defined as sudden, rapid, recurrent, nonrhythmic motor movements or vocalizations, are essential components of Tourette syndrome. Although some tics may be mild, others can cause significant psychosocial, physical, and functional difficulties that affect daily activities. In addition to tics, most affected individuals have coexisting neuropsychological difficulties (attention deficit hyperactivity disorder, obsessive-compulsive disorder, anxiety, mood disorder, disruptive behaviors, schizotypal traits, suicidal behavior, personality disorder, antisocial activities, and sleep disorders) that can further impact social and academic activities or employment.

Increased risk of ADHD in families with ASD

Attention Deficit and Hyperactive Disorder (ADHD) and Autism Spectrum Disorders (ASD) are frequent comorbid neurodevelopmental conditions and the overlap between both disorders remains to be delineated. A more complete understanding of the shared genetic and environmental factors is needed. Using a family-based method, we evaluated the risk of ADHD in a group of relatives with an ASD proband (ASD-) and a group of relatives with an ASD and ADHD proband (ASD+). We enrolled 1245 individuals in the study: 499 probands, their 746 first-degree relatives and 140 controls. We used a multivariate generalized estimating equation (GEE) model, in which the dependent variable was the ADHD diagnosis in the relatives and the independent variable the ASD+ or ASD- in probands. We adjusted for sociodemographic factors (age, sex, IQ) and for the nature of the familial relationship with the affected proband (parent or sibling). Among the probands, there were 287 ASD- and 212 ASD+ individuals. ADHD was more frequent in relatives (19%) than in the control group (7%) (p = 0.001). The risk of ADHD was higher in the ASD+ relatives group than in the ASD- relatives group (GEE model OR 1.58 [95% CI 1.04-2.38], p = 0.032). This result was found in parents (OR 1.96 [95% CI  1.14-3.36], but not in siblings (OR 1.28 [95% CI 0.84-1.94], p = 0.434). Our study provides a representative estimate of the family distribution of ADHD in relatives of ASD probands but supports the modest effect of shared genetic and environmental factors between both disorders.

Tic Severity and Treatment in Children: The Effect of Comorbid Attention Deficit Hyperactivity Disorder and Obsessive Compulsive Behaviors

While attention deficit hyperactivity disorder (ADHD) and obsessive compulsive disorder have been shown to have major impacts on quality of life in individuals with Tourette syndrome, there is comparatively little data on how the presence of these comorbidities influence tic severity and treatment. 114 children (mean age 10.25 years) were extensively clinically phenotyped at a single specialty clinic. While there was no difference in Yale Global Tic Severity Scale (YGTSS) scores in children with versus without ADHD, children with obsessive compulsive behaviors had significantly higher YGTSS scores (p = 0.008). There was a significant correlation between YGTSS scores and age (r = 0.344, p < 0.001). Children with ADHD were more likely to be treated for their tics within the first two years of diagnosis (OR 3.51, p = 0.009). As tic severity does not appear to be greater in children with ADHD, this association may relate to greater overall psychosocial impairment in children with this comorbidity.

Progress in Genetic Studies of Tourette's Syndrome

Tourette's Syndrome (TS) is a complex disorder characterized by repetitive, sudden, and involuntary movements or vocalizations, called tics. Tics usually appear in childhood, and their severity varies over time. In addition to frequent tics, people with TS are at risk for associated problems including attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), anxiety, depression, and problems with sleep. TS occurs in most populations and ethnic groups worldwide, and it is more common in males than in females. Previous family and twin studies have shown that the majority of cases of TS are inherited. TS was previously thought to have an autosomal dominant pattern of inheritance. However, several decades of research have shown that this is unlikely the case. Instead TS most likely results from a variety of genetic and environmental factors, not changes in a single gene. In the past decade, there has been a rapid development of innovative genetic technologies and methodologies, as well as significant progresses in genetic studies of psychiatric disorders. In this review, we will briefly summarize previous genetic epidemiological studies of TS and related disorders. We will also review previous genetic studies based on genome-wide linkage analyses and candidate gene association studies to comment on problems of previous methodological and strategic issues. Our main purpose for this review will be to summarize the new genetic discoveries of TS based on novel genetic methods and strategies, such as genome-wide association studies (GWASs), whole exome sequencing (WES) and whole genome sequencing (WGS). We will also compare the new genetic discoveries of TS with other major psychiatric disorders in order to understand the current status of TS genetics and its relationship with other psychiatric disorders.

Understanding the covariation of tics, attention-deficit/hyperactivity, and obsessive-compulsive symptoms: A population-based adult twin study

Chronic tic disorders (TD), attention-deficit/hyperactivity-disorder (ADHD), and obsessive-compulsive disorder (OCD) frequently co-occur in clinical and epidemiological samples. Family studies have found evidence of shared familial transmission between TD and OCD, whereas the familial association between these disorders and ADHD is less clear. This study aimed to investigate to what extent liability of tics, attention-deficit/hyperactivity, and obsessive-compulsive symptoms is caused by shared or distinct genetic or environmental influences, in a large population-representative sample of Swedish adult twins (n = 21,911). Tics, attention-deficit/hyperactivity, and obsessive-compulsive symptoms showed modest, but significant covariation. Model fitting suggested a latent liability factor underlying the three phenotypes. This common factor was relatively heritable, and explained significantly less of the variance of attention-deficit/hyperactivity symptom liability. The majority of genetic variance was specific rather than shared. The greatest proportion of total variance in liability of tics, attention-deficit/hyperactivity, and obsessive-compulsive symptoms was attributed to specific non-shared environmental influences. Our findings suggest that the co-occurrence of tics and obsessive-compulsive symptoms, and to a lesser extent attention-deficit/hyperactivity symptoms, can be partly explained by shared etiological influences. However, these phenotypes do not appear to be alternative expressions of the same underlying genetic liability. Further research examining sub-dimensions of these phenotypes may serve to further clarify the association between these disorders and identify more genetically homogenous symptom subtypes. © 2016 Wiley Periodicals, Inc.

Impact of co-morbid attention-deficit and hyperactivity disorder on cognitive function in male children with Tourette syndrome: A controlled study

Tourette syndrome (TS) and attention-deficit and hyperactivity disorder (ADHD) are co-morbid neurodevelopmental conditions affecting more commonly male patients. We set out to determine the impact of co-morbid ADHD on cognitive function in male children with TS by conducting a controlled study. Participants included four matched groups of unmedicated children (age range 6-15 years): TS (n=13), TS+ADHD (n=8), ADHD (n=39), healthy controls (n=66). Following clinical assessment, each participant completed a battery of tests from the Wechsler Intelligence Scale for Children-III, the Italian Battery for ADHD, the Tower of London test, the Corsi test, and the Digit Span test. All patient groups reported significantly lower scores than healthy controls across the neuropsychological tests involving executive functions. The TS+ADHD group was the most severely affected, followed by the ADHD group and the TS group, particularly in the tests assessing planning ability, inhibitory function, working memory and visual attention, but not auditory attention. Problems in executive functions are more common in patients with neurodevelopmental disorders than controls. Deficits in planning ability, inhibitory function, working memory and visual attention reported by children with TS appear to be more strongly related to the presence of co-morbid ADHD symptoms than core TS symptoms.

Familiality of Co-existing ADHD and Tic Disorders: Evidence from a Large Sibling Study

Background: The association of attention-deficit/hyperactivity disorder (ADHD) and tic disorder (TD) is frequent and clinically important. Very few and inconclusive attempts have been made to clarify if and how the combination of ADHD+TD runs in families.

Aim: To determine the first time in a large-scale ADHD sample whether ADHD+TD increases the risk of ADHD+TD in siblings and, also the first time, if this is independent of their psychopathological vulnerability in general.

Methods: The study is based on the International Multicenter ADHD Genetics (IMAGE) study. The present sub-sample of 2815 individuals included ADHD-index patients with co-existing TD (ADHD+TD, n = 262) and without TD (ADHD–TD, n = 947) as well as their 1606 full siblings (n = 358 of the ADHD+TD index patients and n = 1248 of the ADHD-TD index patients). We assessed psychopathological symptoms in index patients and siblings by using the Strength and Difficulties Questionnaire (SDQ) and the parent and teacher Conners' long version Rating Scales (CRS). For disorder classification the Parental Account of Childhood Symptoms (PACS-Interview) was applied in n = 271 children. Odds ratio with the GENMOD procedure (PROCGENMOD) was used to test if the risk for ADHD, TD, and ADHD+TD in siblings was associated with the related index patients' diagnoses. In order to get an estimate for specificity we compared the four groups for general psychopathological symptoms.

Results: Co-existing ADHD+TD in index patients increased the risk of both comorbid ADHD+TD and TD in the siblings of these index patients. These effects did not extend to general psychopathology.

Interpretation: Co-existence of ADHD+TD may segregate in families. The same holds true for TD (without ADHD). Hence, the segregation of TD (included in both groups) seems to be the determining factor, independent of further behavioral problems. This close relationship between ADHD and TD supports the clinical approach to carefully assess ADHD in any case of TD.

The relationship between tics, OC, ADHD and autism symptoms: A cross- disorder symptom analysis in Gilles de la Tourette syndrome patients and family-members

Gilles de la Tourette's syndrome (GTS) is a disorder in which obsessive-compulsive (OC), Attention Deficit Hyperactivity Disorder (ADHD) and autism symptoms occur in up to 60% of patients, suggesting shared etiology. We explored the phenotypic structure of tic, OC, ADHD, and autism symptoms as measured by the YGTSS,Y-BOCS,CAARS and AQ, in 225 GTS patients and 371 family members. First, Confirmatory Factor Analyses (CFA) were performed on the symptom structure of each separate symptom scale. Second, the symptom dimensions derived from each scale were combined in one model, and correlations between them were calculated. Using the correlation matrix, Exploratory Factor Analyses (EFA) were performed on the symptom dimensions across the scales. EFA revealed a five factor structure: tic/aggression/symmetry; OC symptoms/compulsive tics/ numbers and patterns; ADHD symptoms; autism symptoms; and hoarding/inattention symptoms. The results are partly in line with the traditional categorical boundaries of the symptom scales used, and partly reveal a symptom structure that cuts through the diagnostic categories. This phenotypic structure might more closely reflect underlying etiologies than a structure that classically describes GTS patients according to absence or presence of comorbid OCD, ADHD and autism, and might inform both future genetic and treatment studies.

Functional jerks, tics, and paroxysmal movement disorders

Functional jerks are among the most common functional movement disorders. The diagnosis of functional jerks is mainly based on neurologic examination revealing specific positive clinical signs. Differentiation from other jerky movements, such as tics, organic myoclonus, and primary paroxysmal dyskinesias, can be difficult. In support of a functional jerk are: acute onset in adulthood, precipitation by a physical event, variable, complex, and inconsistent phenomenology, suggestibility, distractibility, entrainment and a Bereitschaftspotential preceding the movement. Although functional jerks and tics share many similarities, characteristics differentiating tics from functional jerks are: urge preceding the tic, childhood onset, rostrocaudal development of the symptoms, a positive family history of tics, attention-deficit hyperactivity disorder or obsessive-compulsive symptoms, and response to dopamine antagonist medication. To differentiate functional jerks from organic myoclonus, localization of the movements can give direction. Further features in support of organic myoclonus include: insidious onset, simple and consistent phenomenology, and response to benzodiazepines or antiepileptic medication. Primary paroxysmal dyskinesias and functional jerks share a paroxysmal nature. Leading in the differentiation between the two are: a positive family history, in combination with video recordings revealing a consistent symptom pattern in primary paroxysmal dyskinesias. In this chapter functional jerks and their differential diagnoses will be discussed in terms of epidemiology, symptom characteristics, disease course, psychopathology, and supportive neurophysiologic tests.

Association between Tourette syndrome and the dopamine D3 receptor gene rs6280

BACKGROUND

Tourette syndrome (TS) is a complex, heterozygous genetic disorder. The number of molecular genetic studies have investigated several candidate genes, particularly those implicated in the dopamine system. The dopamine D3 receptor (DRD3) gene has been considered as a candidate gene in TS. There was not any report about the association study of TS and DRD3 gene in Han Chinese population. We combined a case-control genetic association analysis and nuclear pedigrees transmission disequilibrium test (TDT) analysis to investigate the association between DRD3 gene rs6280 single nucleotide polymorphisms (SNPs) and TS in a Han Chinese population.

METHODS

A total of 160 TS patients was diagnosed by the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. The DRD3 gene rs6280 SNPs were genotyped by TaqMan SNP genotyping assay technique in all subjects. We used a case-control genetic association analysis to compare the difference in genotype and allele frequencies between 160 TS patients and 90 healthy controls. At the same time, we used TDT analysis to identify the DRD3 gene rs6280 transmission disequilibrium among 101 nuclear pedigrees.

RESULTS

The genotype and allele frequency of DRD3 gene rs6280 SNPs had no statistical difference between control group (90) and TS group (160) (χ2 = 3.647, P = 0.161; χ2 = 0.643, P = 0.423) using Chi-squared test. At the basis of the 101 nuclear pedigrees, TDT analysis showed no transmission disequilibrium of DRD3 gene rs6280 SNPs (χ2 = 0; P = 1).

CONCLUSIONS

Our findings provide no evidence for an association between DRD3 gene rs6280 and TS in the Han Chinese population.

Web-based phenotyping for Tourette Syndrome: Reliability of common co-morbid diagnoses

Collecting phenotypic data necessary for genetic analyses of neuropsychiatric disorders is time consuming and costly. Development of web-based phenotype assessments would greatly improve the efficiency and cost-effectiveness of genetic research. However, evaluating the reliability of this approach compared to standard, in-depth clinical interviews is essential. The current study replicates and extends a preliminary report on the utility of a web-based screen for Tourette Syndrome (TS) and common comorbid diagnoses (obsessive compulsive disorder (OCD) and attention deficit/hyperactivity disorder (ADHD)). A subset of individuals who completed a web-based phenotyping assessment for a TS genetic study was invited to participate in semi-structured diagnostic clinical interviews. The data from these interviews were used to determine participants' diagnostic status for TS, OCD, and ADHD using best estimate procedures, which then served as the gold standard to compare diagnoses assigned using web-based screen data. The results show high rates of agreement for TS. Kappas for OCD and ADHD diagnoses were also high and together demonstrate the utility of this self-report data in comparison previous diagnoses from clinicians and dimensional assessment methods.

Tourette's syndrome and associated disorders: a systematic review

Objective: To compile data on Tourette's syndrome (TS), tics and associated disorders.Methods: A systematic review of the literature was conducted using the 5S levels of organization of healthcare research evidence (systems, summaries, synopses, syntheses, studies), based on the model described by Haynes. The search keywords were Tourette, tics and comorbidity, which were cross-referenced. Studies provided by publishers and articles being processed on July 31, 2013, were also included.Results: Of all studies retrieved during the search, 64 were selected because they analyzed the epidemiology, clinical features and etiopathogenesis of TS and its comorbidities. TS is classified as a hyperkinetic movement disorder, and at least 90% of the patients have neuropsychiatric comorbidities, of which attention deficit hyperactivity and obsessive-compulsive disorders are the most common. The syndrome is clinically heterogeneous and has been associated with a dysfunction of cortico-striatal-thalamic-cortical circuits involving various neurotransmitters. Although its genetic etiology has been widely studied, other factors may be important to understand this syndrome and its associated disorders.Conclusions: TS is a neurodevelopmental disorder that results from the impact of stress factors on a vulnerable biological substrate during the critical periods of neurodevelopment. The study of TS and its comorbidities may contribute, at different levels, to the understanding of several neuropsychiatric disorders of clinical and therapeutic relevance.

Association of the KCNJ5 gene with Tourette Syndrome and Attention-Deficit/Hyperactivity Disorder

Linkage and association of Tourette Syndrome (TS) and Attention-Deficit/Hyperactivity Disorder (ADHD) have previously been reported in the 11q24 chromosomal region. To identify the risk gene within the region we studied the potassium inwardly-rectifying channel J5 (KCNJ5) gene in a sample of 170 nuclear families with TS. We genotyped eight markers across the gene and observed biased transmission of haplotypes from parents to probands in this sample. We then tested these markers in an independent sample of 242 nuclear families with ADHD and found the same haplotype was significantly over transmitted to ADHD probands. Screening of the coding region of KCNJ5 in 48 probands with TS did not identify any variation that could explain the association of the haplotype. We also genotyped two microsatellite markers, one in the promoter and the other in the 3' region and found no evidence for association for either marker for TS, however, we found significant evidence for association with the 3' repeat and ADHD. A small gene (c11orf45) of unknown function lies within the first intron of KCNJ5 that is transcribed in the opposite orientation and this gene may regulate the expression of KCNJ5. We studied the correlation of the expression of KCNJ5 and the antisense transcript in brain tissues from control individuals and found that the antisense transcript and the short KCNJ5 isoform are co-expressed in three brain regions. The results of this study indicate that KCNJ5 is associated with TS and ADHD in our samples, however, the functional variant(s) remain to be identified.

Association of tyrosyl-DNA phosphodiesterase 1 polymorphism with Tourette syndrome in Taiwanese patients

BACKGROUND

Genetic, environmental, immunological, and hormonal factors contribute to the etiology of Tourette syndrome (TS). From the genetic standpoint, TS is a heterogeneous disorder. In our previous study, we found that a single nucleotide polymorphism (SNP) of x-ray repair cross-complementing group 1 (XRCC1), a DNA repair gene, was associated with TS. Previous studies also showed that tyrosyl-DNA phosphodiesterase 1 (TDP1) interacts with XRCC1 to repair damaged DNA. However, the relationship between TS and SNPs of TDP1 gene is unknown. Therefore, the aim of this study was to test the hypothesis that if the TDP1 SNP, rs28365054 (c.400G>A, Ala134Thr), was associated with TS or not.

METHODS

A case-control study was designed to test the hypothesis. A total of 122 TS children and 106 normal children participated in the study. We used polymerase chain reaction to identify the SNP, rs28365054, of the TDP1 gene in the TS patients and the normal children.

RESULTS

A polymorphism at position rs28365054 in the TDP1 gene had a significant difference (P < 0.05) in the genotype distributions between the TS patients and the control group. The AG genotype was a risk factor for TS with an odds ratio of 2.26 for the AG versus AA genotype (95% CI 1.08-4.72).

CONCLUSION

The findings of this study suggested that variants in the TDP1 gene might play a role in TS susceptibility.

CNV analysis in Tourette syndrome implicates large genomic rearrangements in COL8A1 and NRXN1

Tourette syndrome (TS) is a neuropsychiatric disorder with a strong genetic component. However, the genetic architecture of TS remains uncertain. Copy number variation (CNV) has been shown to contribute to the genetic make-up of several neurodevelopmental conditions, including schizophrenia and autism. Here we describe CNV calls using SNP chip genotype data from an initial sample of 210 TS cases and 285 controls ascertained in two Latin American populations. After extensive quality control, we found that cases (N = 179) have a significant excess (P = 0.006) of large CNV (>500 kb) calls compared to controls (N = 234). Amongst 24 large CNVs seen only in the cases, we observed four duplications of the COL8A1 gene region. We also found two cases with ∼400 kb deletions involving NRXN1, a gene previously implicated in neurodevelopmental disorders, including TS. Follow-up using multiplex ligation-dependent probe amplification (and including 53 more TS cases) validated the CNV calls and identified additional patients with rearrangements in COL8A1 and NRXN1, but none in controls. Examination of available parents indicates that two out of three NRXN1 deletions detected in the TS cases are de-novo mutations. Our results are consistent with the proposal that rare CNVs play a role in TS aetiology and suggest a possible role for rearrangements in the COL8A1 and NRXN1 gene regions.

Genetic susceptibility and neurotransmitters in Tourette syndrome

Family studies have consistently shown that Tourette syndrome (TS) is a familial disorder and twin studies have clearly indicated a genetic contribution in the etiology of TS. Whereas early segregation studies of TS suggested a single-gene autosomal dominant disorder, later studies have pointed to more complex models including additive and multifactorial inheritance and likely interaction with genetic factors. While the exact cellular and molecular base of TS is as yet elusive, neuroanatomical and neurophysiological studies have pointed to the involvement of cortico-striato-thalamocortical circuits and abnormalities in dopamine, glutamate, gamma-aminobutyric acid, and serotonin neurotransmitter systems, with the most consistent evidence being available for involvement of dopamine-related abnormalities, that is, a reduction in tonic extracellular dopamine levels along with hyperresponsive spike-dependent dopamine release, following stimulation. Genetic and gene expression findings are very much supportive of involvement of these neurotransmitter systems. Moreover, intriguingly, genetic work on a two-generation pedigree has opened new research pointing to a role for histamine, a so far rather neglected neurotransmitter, with the potential of the development of new treatment options. Future studies should be aimed at directly linking neurotransmitter-related genetic and gene expression findings to imaging studies (imaging genetics), which enables a better understanding of the pathways and mechanisms through which the dynamic interplay of genes, brain, and environment shapes the TS phenotype.

Tourette syndrome in youth with and without obsessive compulsive disorder and attention deficit hyperactivity disorder

Chronic tic disorders (TD) are consistently found to have high rates of comorbidity with obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD). The purpose of this study is to compare the severity of TD only to TD with comorbid OCD or ADHD based on severity of tics, measures of psychopathology and additional comorbid diagnoses. Baseline data from 158 youth with a chronic TD who participated in two longitudinal studies were examined. Fifty-three percent (N = 85) of the youth also met criteria for a diagnosis of OCD, 38.6 % (n = 61) met criteria for ADHD and 24.1 % (N = 38) met criteria for both. Measures of interest addressed severity of tics, symptoms of anxiety, depression, ADHD, psychosocial stress, global functioning and the presence of comorbid diagnoses. Youth with comorbid TD and OCD were characterized by more severe tics, increased levels of depressive and anxious symptoms, heightened psychosocial stress and poorer global functioning. Youth with comorbid TD and ADHD did not differ from those with TD alone on measures of tic severity, but experienced greater psychosocial stress and poorer global functioning. Subjects with comorbid TD and OCD had more internalizing disorders than those without OCD, while those with comorbid ADHD were more likely to meet criteria for oppositional defiant disorder. TD with OCD is a more severe subtype of TD than TD without OCD. TD with ADHD is associated with higher psychosocial stress and more externalizing behaviors. Further research is needed into the underlying relationships between these closely associated conditions.

Review of prevalence studies of tic disorders: methodological caveats

INTRODUCTION

Tic disorders are neurodevelopmental disorders of childhood associated with psychiatric comorbidity and academic problems. Estimating the prevalence and understanding the epidemiology of tic disorders is more complex than was once thought. Until fairly recently, tic disorders were thought to be rare, but today tics are believed to be the most common movement disorder, with 0.2-46.3% of schoolchildren experiencing tics during their lifetime. Tentative explanations for differing prevalence estimates include the multidimensional nature of tics with a varied and heterogeneous presentation, and the use of different epidemiological methods and study designs.

METHODS

Literature review and analysis of methodological issues pertinent to epidemiological studies of tic disorders.

RESULTS

Epidemiological studies of tic disorders were reviewed, and the main elements of epidemiological studies, including sample selection, case ascertainment strategy, definition of tic disorders, and the degree of coverage of the eligible population (i.e., the response rate) were examined.

DISCUSSION

In order to improve the quality of epidemiological studies of tic disorders, a number of recommendations were made, including but not limited to a review of the diagnostic criteria for tic disorders, and inclusion of new tic disorder categories for those with tics of secondary etiology.

Update on attention-deficit/hyperactivity disorder and tic disorders: a review of the current literature

Tic disorders impact quality of life, but when they are co-occurring with attention-deficit/hyperactivity disorder, the combined impact takes a toll on psychosocial functioning and adds another layer of complexity to treatment approaches. A review of the current literature supports evidence of a unique relationship between comorbid attention-deficit/hyperactivity disorder and tic disorders, emphasizing the intricate phenotype and impairment associated with these co-occurring conditions. The complexity of these symptoms requires careful diagnosis and appropriate treatment as determined by the level of impairment and can include pharmacotherapy, behavioral interventions, or a combination of therapies. To achieve the greatest benefits in improving quality of life and eliminating further comorbidity, an ideal treatment plan would include a comprehensive evaluation as well as a hierarchical treatment approach involving education of the child, family, and teachers; careful medication management; and cognitive and behavioral training.

The familial association of tourette's disorder and ADHD: the impact of OCD symptoms

Tourette's disorder (TD) frequently co-occurs with attention-deficit/hyperactivity disorder (ADHD) and obsessive compulsive disorder (OCD). While the relationship between TD and OCD suggests that they share etiological factors, the exact relationship between TD and ADHD is less clear. The goal of the current analyses was to understand better the familial relationship between DSM-IV ADHD and TD. Direct interview diagnostic data from a case-control study of 692 relatives of 75 comorbid TD and ADHD (TD + ADHD), 74 TD without ADHD (TD Only), 41 ADHD without TD (ADHD Only), and 49 control probands were analyzed. Hierarchical loglinear modeling was used to explore association patterns between TD, ADHD, and OCD or sub-clinical OCD (OCD/OCDsub) diagnoses among the 190 affected probands and their 538 relatives. The presence of OCD or OCDsub diagnosis in a proband was associated with a significantly increased risk of comorbid TD + ADHD in his/her relatives. The finding of an association between TD, ADHD and a proband OCD/OCDsub diagnosis was unexpected. The current results suggest that TD, ADHD, and OCD symptoms have overlapping neurobiology when occurring in families of TD and/or ADHD probands.

Recent advances in Tourette syndrome

PURPOSE OF REVIEW

This review considers the recent literature pertaining to the neurobiology, genetics and treatment of Tourette syndrome.

RECENT FINDINGS

Over the last several years, both neuropathological and genetic findings have further focused attention on long-standing hypotheses regarding the role of the basal ganglia in causing tics and Tourette syndrome. Moreover, although the field awaits the results the first large-scale genetic studies, recent findings have already mirrored developments in the neuropsychiatric genetics literature more broadly, highlighting the value of the study of rare variation and the overlap of risks among seemingly disparate diagnostic categories. Finally, treatment studies have underscored the importance of cognitive-behavioral as well as pharmacological interventions for the treatment of tic disorders.

SUMMARY

Recent findings have led to novel, testable hypotheses regarding the molecular and cellular mechanisms underlying Tourette syndrome. These, in turn, have begun to provide new avenues to conceptualizing treatment strategies. Although the development of additional medication options is a pressing need, recent data has demonstrated both the safety and efficacy of nonpharmacological approaches.

European clinical guidelines for Tourette syndrome and other tic disorders. Part I: assessment

A working group of the European Society for the Study of Tourette Syndrome (ESSTS) has developed the first European assessment guidelines of Tourette Syndrome (TS). The available literature including national guidelines was thoroughly screened and extensively discussed in the expert group of ESSTS members. Detailed clinical assessment guidelines of tic disorders and their comorbidities in both children and adults are presented. Screening methods that might be helpful and necessary for specialists' differential diagnosis process are suggested in order to further analyse cognitive abilities, emotional functions and motor skills. Besides clinical interviews and physical examination, additional specific tools (questionnaires, checklists and neuropsychological tests) are recommended.

Obsessive-compulsive disorder comorbidity: clinical assessment and therapeutic implications

Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder affecting approximately 1-3% of the population. OCD is probably an etiologically heterogeneous condition. Individuals with OCD frequently have additional psychiatric disorders concomitantly or at some time during their lifetime. Recently, some authors proposed an OCD sub-classification based on comorbidity. An important issue in assessing comorbidity is the fact that the non-response to treatment often involves the presence of comorbid conditions. Non-responsive patients are more likely to meet criteria for comorbid axis I or axis II disorders and the presence of a specific comorbid condition could be a distinguishing feature in OCD, with influence on the treatment adequacy and outcome.

Familiality of Tourette syndrome, obsessive-compulsive disorder, and attention-deficit/hyperactivity disorder: heritability analysis in a large sib-pair sample

OBJECTIVE

Tourette syndrome (TS) is a neuropsychiatric disorder with a genetic component that is highly comorbid with obsessive-compulsive disorder (OCD) and attention deficit/hyperactivity disorder (ADHD). However, the genetic relations between these disorders have not been clearly elucidated. This study examined the familial relations among TS, OCD, and ADHD in a large sample of TS families.

METHOD

Parent-offspring concordance of TS, OCD, and ADHD was examined in 952 individuals from 222 TS-affected sib-pair families originally collected for genetic studies using logistic regression with generalized estimating equations to control for correlated data. Variance components methods were used to estimate the heritability and genetic and environmental correlations among TS, OCD, and ADHD. Bilineal families where both parents had TS or OCD were excluded.

RESULTS

OCD and ADHD were highly heritable in these TS families. There were significant genetic correlations between TS and OCD and between OCD and ADHD, but not between TS and ADHD. In addition, significant environmental correlations were found between TS and ADHD and between OCD and ADHD. Parental OCD + ADHD was associated with offspring OCD + ADHD.

CONCLUSIONS

This study provides further evidence for a genetic relation between TS and OCD and suggests that the observed relation between TS and ADHD may due in part be to a genetic association between OCD and ADHD and in part due to shared environmental factors.

The genetics of child psychiatric disorders: focus on autism and Tourette syndrome

Investigations into the genetics of child psychiatric disorders have finally begun to shed light on molecular and cellular mechanisms of psychopathology. The first strains of success in this notoriously difficult area of inquiry are the result of an increasingly sophisticated appreciation of the allelic architecture of common neuropsychiatric and neurodevelopmental disorders, the consolidation of large patient cohorts now beginning to reach sufficient size to power reliable studies, the emergence of genomic tools enabling comprehensive investigations of rare as well as common genetic variation, and advances in developmental neuroscience that are fueling the rapid translation of genetic findings.

Repetitive behaviours in patients with Gilles de la Tourette syndrome: tics, compulsions, or both?

BACKGROUND

Repetitive behaviours (RB) in patients with Gilles de la Tourette syndrome (GTS) are frequent. However, a controversy persists whether they are manifestations of obsessive-compulsive disorder (OCD) or correspond to complex tics.

METHODS

166 consecutive patients with GTS aged 15-68 years were recruited and submitted to extensive neurological, psychiatric and psychological evaluations. RB were evaluated by the YBOCS symptom checklist and Mini International Neuropsychiatric Interview (M.I.N.I), and classified on the basis of a semi-directive psychiatric interview as compulsions or tics.

RESULTS

RB were present in 64.4% of patients with GTS (107/166) and categorised into 3 major groups: a 'tic-like' group (24.3%-40/166) characterised by RB such as touching, counting, 'just right' and symmetry searching; an 'OCD-like' group (20.5%-34/166) with washing and checking rituals; and a 'mixed' group (13.2%-22/166) with both 'tics-like' and 'OCD-like' types of RB present in the same patient. In 6.3% of patients, RB could not be classified into any of these groups and were thus considered 'undetermined'.

CONCLUSIONS

The results confirm the phenomenological heterogeneity of RB in GTS patients and allows to distinguish two types: tic-like behaviours which are very likely an integral part of GTS; and OCD-like behaviours, which can be considered as a comorbid condition of GTS and were correlated with higher score of complex tics, neuroleptic and SSRIs treatment frequency and less successful socio-professional adaptation. We suggest that a meticulous semiological analysis of RB in GTS patients will help to tailor treatment and allow to better classify patients for future pathophysiologic studies.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00169351.

ADHD prevalence and association with hoarding behaviors in childhood-onset OCD

BACKGROUND

It has been suggested that attention-deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD), both neurodevelopmental disorders with onset in childhood, are highly comorbid, but previous studies examining ADHD and OCD comorbidity have been quite variable, partly because of inconsistency in excluding individuals with tic disorders. Similarly, ADHD has been postulated to be associated with hoarding although this potential relationship is largely methodologically unexplored. This study aimed to examine the prevalence of ADHD among individuals with childhood-onset OCD but without comorbid tic disorders, as well as to examine the relationship between clinically significant hoarding behaviors (hoarding) and ADHD.

METHOD

ADHD prevalence rates and the relationship between ADHD and hoarding were examined in 155 OCD-affected individuals (114 probands and 41 relatives, age range 4-82 years) recruited for genetic studies and compared to pooled prevalence rates derived from previously published studies.

RESULTS

In total, 11.8% met criteria for definite ADHD, whereas an additional 8.6% had probable or definite ADHD (total=20.4%). In total, 41.9% of participants with ADHD also had hoarding compared to 29.2% of participants without ADHD. Hoarding was the only demographic or clinical variable independently associated with ADHD (odds ratio=9.54, P<0.0001).

CONCLUSION

ADHD rates were elevated in this sample of individuals with childhood-onset OCD compared to the general population rate of ADHD, and there was a strong association between ADHD and clinically significant hoarding behavior. This association is consistent with recent studies suggesting that individuals with hoarding may exhibit substantial executive functioning impairments and/or abnormalities, including attentional problems.

Should an obsessive-compulsive spectrum grouping of disorders be included in DSM-V?

The obsessive-compulsive (OC) spectrum has been discussed in the literature for two decades. Proponents of this concept propose that certain disorders characterized by repetitive thoughts and/or behaviors are related to obsessive-compulsive disorder (OCD), and suggest that such disorders be grouped together in the same category (i.e. grouping, or "chapter") in DSM. This article addresses this topic and presents options and preliminary recommendations to be considered for DSM-V. The article builds upon and extends prior reviews of this topic that were prepared for and discussed at a DSM-V Research Planning Conference on Obsessive-Compulsive Spectrum Disorders held in 2006. Our preliminary recommendation is that an OC-spectrum grouping of disorders be included in DSM-V. Furthermore, we preliminarily recommend that consideration be given to including this group of disorders within a larger supraordinate category of "Anxiety and Obsessive-Compulsive Spectrum Disorders." These preliminary recommendations must be evaluated in light of recommendations for, and constraints upon, the overall structure of DSM-V.

Predictive factors for familiality in a Danish clinical cohort of children with Tourette syndrome

Tourette syndrome (TS) is a chronic, neurobiological disease, characterized by the presence of motor and vocal tics and it is often accompanied by associated symptoms. The two best-known co-morbidities are Obsessive-Compulsive Disorder (OCD) and Attention Deficit Hyperactivity Disorder (ADHD). The fact that TS aggregates strongly in families suggests that family members share either genetic and/or environmental risk factors contributing to TS. Numerous studies have been performed to examine the familiality in TS, but clear-cut factors to predict hereditability in TS have not been found yet. We have examined a large Danish clinical cohort of children with TS (N=307). Validated diagnostic instruments were used to assess the presence of co-morbidities in the children with TS. A three-generation pedigree was drawn for all the probands and through reports from the family, a family history and the frequency of affected relatives was noted. The rates of tics, symptoms of OCD, and ADHD among relatives are similar to the rates found in other countries and are higher than in the general population. Although the role of sex in determining the phenotype has to be examined more thoroughly, we found that male relatives were more likely to have tics and female relatives were more likely to have symptoms of OCD. When comparing the relatives to male patients with relatives to female patients, there were no differences in the rates of symptoms, apart from symptoms of ADHD that were more frequent in second-degree relatives to female patients. The severity of tics and the presence of co-morbidity did not seem to predict the familiality of TS and its associated symptoms.

Phenotypic and measurement influences on heritability estimates in childhood ADHD

Twin studies described a strongly heritable component of attention-deficit/hyperactivity disorder (ADHD) in children and adolescents. However, findings varied considerably between studies. In addition, ADHD presents with a high rate of comorbid disorders and associated psychopathology. Therefore, this literature review reports findings from population-based twin studies regarding the influence of subtypes, assessment instruments, rater effects, sex differences, and comorbidity rates on ADHD heritability estimates. In addition, genetic effects on the persistence of ADHD are discussed. By reviewing relevant factors influencing heritability estimates more homogeneous subtypes relevant for molecular genetic studies can be elicited. A systematic search of population-based twin studies in ADHD was performed, using the databases PubMed and PsycInfo. Results of family studies were added in case insufficient or contradictory findings were obtained in twin studies. Heritability estimates were strongly influenced by rater effects and assessment instruments. Inattentive and hyperactive-impulsive symptoms were likely influenced by common as well as specific genetic risk factors. Besides persistent ADHD, ADHD accompanied by symptoms of conduct or antisocial personality disorder might be another strongly genetically determined subtype, however, family environmental risk factors have also been established for this pattern of comorbidity.

The genetics of Tourette syndrome: a review

OBJECTIVES

This article summarizes and evaluates recent advances in the genetics of Gilles de la Tourette syndrome (GTS).

METHODS

This is a review of recent literature focusing on (1) the genetic etiology of GTS; (2) common genetic components of GTS, attention deficit hyperactivity disorder (ADHD), and obsessive compulsive disorder (OCD); (3) recent linkage studies of GTS; (4) chromosomal translocations in GTS; and (5) candidate gene studies.

RESULTS

Family, twin, and segregation studies provide strong evidence for the genetic nature of GTS. GTS is a heterogeneous disorder with complex inheritance patterns and phenotypic manifestations. Family studies of GTS and OCD indicate that an early-onset form of OCD is likely to share common genetic factors with GTS. While there apparently is an etiological relationship between GTS and ADHD, it appears that the common form of ADHD does not share genetic factors with GTS. The largest genome wide linkage study to date observed evidence for linkage on chromosome 2p23.2 (P=3.8x10(-5)). No causative candidate genes have been identified, and recent studies suggest that the newly identified candidate gene SLITRK1 is not a significant risk gene for the majority of individuals with GTS.

CONCLUSION

The genetics of GTS are complex and not well understood. The Genome Wide Association Study (GWAS) design can hopefully overcome the limitations of linkage and candidate gene studies. However, large-scale collaborations are needed to provide enough power to utilize the GWAS design for discovery of causative mutations. Knowledge of susceptibility mutations and biological pathways involved should eventually lead to new treatment paradigms for GTS.

Clinical phenomenology and phenotype variability in Tourette syndrome

Tourette syndrome (TS) is a neurodevelopmental disorder with a rich phenomenology that includes simple and complex motor and vocal tics as well as multiple comorbidities. From a nosological perspective, it is evident that a continuum of tic severity exists, of which TS is the most severe and rare form, while transient tics and chronic tics represent milder forms. From a psychopathology perspective, TS is often concurrent with obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD); these disorders appear to define TS "types" TS only, TS+OCD, and TS+OCD+ADHD. Additional clinical aspects of TS include more frequent than expected occurrence of anger episodes, anxiety disorders, mood disorders, impulse control disorders, learning disorders, and pervasive developmental disorders. Data reduction techniques have been used more recently to define a "simple" and "complex" tic symptom clusters or factors. Phenomenologic approaches can be used in TS to guide future pathophysiologic research.

Anxiety in boys with attention-deficit/hyperactivity disorder with and without chronic multiple tic disorder

OBJECTIVE

This study examined the psychosocial and behavioral concomitants of anxiety in clinic-referred boys with attention-deficit/hyperactivity disorder (ADHD) with and without chronic multiple tic disorder (CMTD).

METHOD

ADHD boys with (n = 65) and without (n = 94) CMTD were evaluated with measures of psychiatric symptoms, mental health risk factors, and academic and social performance.

RESULTS

Boys with CMTD evidenced more severe anxiety and less social competence and were more likely to be living with only one biological parent than the ADHD Only group, but the magnitude of group differences was generally small. The severity of generalized anxiety, separation anxiety, social phobia, and obsessive-compulsive symptoms were uniquely associated with a different pattern of risk factors, and there was some evidence that these patterns differed for the two groups of boys.

CONCLUSION

Boys with CMTD had a relatively more severe and complex pattern of anxiety that was associated with different clinical features, all of which suggests that ADHD plus CMTD might better be conceptualized as a distinct clinical entity from ADHD Only. However, findings from the extant literature are mixed, and therefore this remains a topic for further study.

Adults with Tourette's syndrome with and without attention deficit hyperactivity disorder

OBJECTIVE

Comorbidity between Tourette's syndrome (TS) and attention deficit hyperactivity disorder (ADHD) is high. In children, those with both TS+ADHD fare less well than those with TS-only on measures of both psychopathology and behaviour. The objective of this study was to document such measures in adult patients.

METHOD

Eighty adults with TS-only were compared to 64 with TS+ADHD using a clinical interview and standardised measures of depression, anxiety and obsessionality.

RESULTS

The two groups were no different on measures of TS severity. TS+ADHD patients had significantly more depression, anxiety, obsessive-compulsive behaviour and maladaptive behaviours than patients with TS-only. There were also significant differences in the incidence of copro- and echo-phenomena and family history of ADHD.

CONCLUSION

The finding of increased overall behavioural difficulties and psychopathology in adult patients with TS+ADHD when compared with TS-only is in agreement with previous findings in children with TS. Appropriate treatment of ADHD in TS patients during childhood may prevent many behavioural problems in adulthood.

Prenatal and perinatal morbidity in children with Tourette syndrome and attention-deficit hyperactivity disorder

OBJECTIVE

Tourette syndrome (TS) and attention-deficit hyperactivity disorder (ADHD) are frequently seen in combination, though the cause of comorbidity is uncertain. Low birth weight is a known risk factor for ADHD. The objective of the study was to assess the association between pre- and perinatal morbidity and the comorbid diagnosis of ADHD in children with TS.

METHOD

A nested case-control study of children evaluated for TS at a subspecialty clinic was performed. Cases were defined as children with TS and ADHD; controls had TS without ADHD. Exposure to pre- and perinatal morbidity was assessed using demographic information booklets completed by parents before the diagnostic interview.

RESULTS

Three hundred fifty-three children were included, 181 cases and 172 controls. Children with TS and ADHD had a greater odds of exposure to low birth weight status, prematurity, breathing problems, and maternal smoking compared with children with TS only. A multivariable logistic regression model found adjusted odds ratios for the comorbid diagnosis of TS and ADHD of 2.74 (95% CI 1.03-7.29, p = .04) in children born low birth weight, and of 2.43 (95% CI 1.23-4.82, p = .01) for children exposed to maternal smoking.

CONCLUSION

In children with TS, there is a greater odds of comorbid ADHD in children born with low birth weight or with exposure to maternal smoking. The commonality of risk factors for ADHD only and tic-related ADHD supports a common underlying neurobiology. Women with fetuses at risk for TS should avoid smoking and preventable causes of low birth weight to minimize the risk of comorbid ADHD.

Comparative study of children with ADHD only, autism spectrum disorder + ADHD, and chronic multiple tic disorder + ADHD

OBJECTIVE

Identification of differences among children with ADHD only, autism spectrum disorder (ASD)+ADHD, and chronic multiple tic disorder (CMTD)+ADHD may lead to better understanding of clinical phenotypes.

METHOD

Children were evaluated using the parent- and teacher-completed questionnaires.

RESULTS

All three groups were highly similar in severity of oppositional defiant disorder and conduct disorder symptoms; however, the ASD+ADHD group generally exhibited the most severe anxiety, although the CMTD+ADHD group had the most severe generalized anxiety. The two comorbid groups had the most involved medical histories and the greatest likelihood of a family history of psychopathology.

CONCLUSION

Groups differed in clinically meaningful ways, and the apparent association between tics and anxiety may explain in part the elevated levels of anxiety in both comorbid groups. Collectively, results suggest that ADHD may be better conceptualized as a family of interrelated syndromes defined in part by comorbid conditions and that continued research is clearly warranted.

Performance of the adolescent obsessive-compulsive scale in a community survey

Obsessive-compulsive behavior was studied in a cohort of N=570 subjects who had been assessed at three times between adolescence and young adulthood. Based on the Youth Self-Report (YSR) and the Young Adult Self-Report (YASR), the adolescent obsessive-compulsive scale (AOCS) was defined. At each of the three assessments, subjects scoring above the cut-off score of the 90th percentile of the AOCS were identified and compared to the rest of the sample serving as control group. The risk group was clearly more abnormal in both domains of internalizing and externalizing across time. Various psychiatric disorders in young adulthood were predicted by the AOCS. However, concomitant general psychopathology also contributed strongly to the prediction. Parent and youth agreement on group membership was rather low. Stability of group assignment across time was significantly increased. The AOCS is a promising instrument both for epidemiological and clinical studies. Its content and predictive validity deserves further studies.

Chromosome 5 and Gilles de la Tourette syndrome: Linkage in a large pedigree and association study of six candidates in the region

Gilles de la Tourette Syndrome (TS) is a neuropsychiatric disorder characterized by both motor and vocal tics. In our previous genome scan for TS we identified evidence for linkage to the centromeric region of chromosome 5 in a single large family of 32 individuals with 10 family members with TS or chronic multiple tics (CMT). In this paper we report further analyses of the 5p-centromeric region in this pedigree. An additional 11 family members were identified and screened for TS. Using a set of 14 microsatellite markers we refined the linked region to a approximately 28 Mb interval between the markers D5S1506 and D5S76. A set of six candidate genes located in this region were selected to be tested for genetic association with TS. These genes were GDNF, ITGA1, ISL1, FGF10, HCN1 and SLC1A3. The TDT statistic was used for the association tests in a sample of 171 independent nuclear families with 241 affected children with TS. We found no evidence for an association between TS and markers in these genes in this sample of families. This study represents the first efforts to narrow the linkage region in the extended pedigree and the first tests of candidate genes in the chromosome 5 region linked to TS.