A Family Genetic Study of Obsessive Compulsive Disorder in Youth

OBJECTIVE

To use a family genetic study to evaluate familial risk of obsessive compulsive disorder (OCD) and common comorbid illnesses in first-degree relatives of pediatric-onset probands with primary OCD.

METHOD

One hundred and thirty youth with OCD and their 133 siblings and 241 parents and 49 pediatric controls were directly evaluated along multiple domains including psychopathology using structured diagnostic interviews and clinical corroboration.

RESULTS

Rates of anxiety, mood, disruptive behavior, and tic disorders were markedly elevated in the probands while rates in siblings were elevated at rates between the probands and controls. Twenty six percent of first-degree relatives had clinical OCD, 9% had chronic tics or Tourette's disorder, and 21% met criteria for ADHD.

CONCLUSION

Rates of familial transmission of OCD and common comorbid illnesses were significantly higher in our pediatric-onset probands than rates reported in the literature in relatives of those with adult-onset OCD.

Direct additive genetics and maternal effect contribute to the risk of Tourette disorder

BACKGROUND

Risk for Tourette disorder, and chronic motor or vocal tic disorders (referenced here inclusively as CTD), arise from a combination of genetic and environmental factors. While multiple studies have demonstrated the importance of direct additive genetic variation for CTD risk, little is known about the role of cross-generational transmission of genetic risk, such as maternal effect, which is not transmitted via the inherited parental genomes. Here, we partition sources of variation on CTD risk into direct additive genetic effect (narrow-sense heritability) and maternal effect.

METHODS

The study population consists of 2 522 677 individuals from the Swedish Medical Birth Register, who were born in Sweden between 1 January 1973 and 31 December 2000, and followed for a diagnosis of CTD through 31 December, 2013. We used generalised linear mixed models to partition the liability of CTD into: direct additive genetic effect, genetic maternal effect and environmental maternal effect.

RESULTS

We identified 6227 (0.2%) individuals in the birth cohort with a CTD diagnosis. A study of half-siblings showed that maternal half-siblings had twice higher risk of developing a CTD compared with paternal ones. We estimated 60.7% direct additive genetic effect (95% credible interval, 58.5% to 62.4%), 4.8% genetic maternal effect (95% credible interval, 4.4% to 5.1%) and 0.5% environmental maternal effect (95% credible interval, 0.2% to 7%).

CONCLUSIONS

Our results demonstrate genetic maternal effect contributes to the risk of CTD. Failure to account for maternal effect results in an incomplete understanding of the genetic risk architecture of CTD, as the risk for CTD is impacted by maternal effect which is above and beyond the risk from transmitted genetic effect.

Phenotypic Impact of Rare Potentially Damaging Copy Number Variation in Obsessive-Compulsive Disorder and Chronic Tic Disorders

BACKGROUND

Recent studies report an important-and previously underestimated-role of rare variation in risk of obsessive-compulsive disorder (OCD) and chronic tic disorders (CTD). Using data from a large epidemiological study, we evaluate the distribution of potentially damaging copy number variation (pdCNV) in OCD and CTD, examining associations between pdCNV and the phenotypes of probands, including a consideration of early- vs. late-diagnoses.

METHOD

The Obsessive-Compulsive Inventory-Revised (OCI-R) questionnaire was used to ascertain psychometric profiles of OCD probands. CNV were identified genome-wide using chromosomal microarray data.

RESULTS

For 993 OCD cases, 86 (9%) were identified as pdCNV carriers. The most frequent pdCNV found was at the 16p13.11 region. There was no significant association between pdCNV and the OCI-R total score. However, pdCNV was associated with Obsessing and Checking subscores. There was no significant difference in pdCNV frequency between early- vs. late-diagnosed OCD probands. Of the 217 CTD cases, 18 (8%) were identified as pdCNV carriers. CTD probands with pdCNV were significantly more likely to have co-occurring autism spectrum disorder (ASD).

CONCLUSIONS

pdCNV represents part of the risk architecture for OCD and CTD. If replicated, our findings suggest pdCNV impact some OCD symptoms. Genes within the 16p13.11 region are potential OCD risk genes.

Cohort profile: Epidemiology and Genetics of Obsessive-compulsive disorder and chronic tic disorders in Sweden (EGOS)

PURPOSE

The EGOS study (Epidemiology and Genetics of Obsessive-compulsive disorder and chronic tic disorders in Sweden) is a large-scale, epidemiological, prospective cohort that is used to identify genetic and environmental risk factors in the etiology of obsessive-compulsive disorder (OCD) and chronic tic disorders (CTD).

METHODS

Individuals born between January 1954 and December 1998 with at least two diagnoses of OCD or CTD at different timepoints in the National Patient Register (NPR), and followed between January 1997 and December 2012, represent the EGOS source population (n = 20,374). The Swedish Multi-Generation Registry (MGR) are then used to define family relatedness for all cases and additional phenotypic and demographic data added to the resultant database. To create an epidemiologically valid subset of the source cohort that also includes biospecimens and additional phenotyping, we contact cases from within the source population. To date, 6832 invitations have been sent out and 1853 (27%) have elected to participate in the EGOS biospecimen collection.

RESULTS

To date, 1608 biological samples have been collected, of which 1249 are genotyped and 832 supplementary Obsessive-Compulsive Inventory-Revised (OCI-R) and/or Florida Obsessive-Compulsive Inventory (FOCI) have been completed by individuals with OCD and/or CTD, age 16-64 years. DNA samples are genotyped using Infinium Global Screening Array and will undergo whole-exome sequencing in the future. Detailed information is available for each individual through linkage to the Swedish national registers, e.g., identification of additional psychiatric diagnoses, medical diagnoses, birth-related variables, and relevant demographic and social data.

CONCLUSION

EGOS benefits from a genetically homogeneous sample with epidemiological ascertainment, minimizing the risk of confounding due to population stratification on ascertainment bias. In addition, this study is built upon clinical diagnoses of OCD and CTD in specialized psychiatric care, which reduces further biases and case misclassification.

Maternal polycystic ovary syndrome and risk of neuropsychiatric disorders in offspring: prenatal androgen exposure or genetic confounding?

BACKGROUND

Maternal polycystic ovary syndrome (PCOS) has been proposed as a model for investigating the role of prenatal androgen exposure in the development of neuropsychiatric disorders. However, women with PCOS are at higher risk of developing psychiatric conditions and previous studies are likely confounded by genetic influences.

METHODS

A Swedish nationwide register-based cohort study was conducted to disentangle the influence of prenatal androgen exposure from familial confounding in the association between maternal PCOS and offspring attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorders (ASD), and Tourette's disorder and chronic tic disorders (TD/CTD). PCOS-exposed offspring (n = 21 280) were compared with unrelated PCOS-unexposed offspring (n = 200 816) and PCOS-unexposed cousins (n = 17 295). Associations were estimated with stratified Cox regression models.

RESULTS

PCOS-exposed offspring had increased risk of being diagnosed with ADHD, ASD, and TD/CTD compared with unrelated PCOS-unexposed offspring. Associations were stronger in girls for ADHD and ASD but not TD/CTD [ADHD: adjusted hazard ratio (aHR) = 1.61 (95% confidence interval (CI) 1.31-1.99), ASD: aHR = 2.02 (95% CI 1.45-2.82)] than boys [ADHD: aHR = 1.37 (95% CI 1.19-1.57), ASD: aHR = 1.46 (95% CI 1.21-1.76)]. For ADHD and ASD, aHRs for girls were stronger when compared with PCOS-unexposed cousins, but slightly attenuated for boys.

CONCLUSIONS

Estimates were similar when accounting for familial confounding (i.e. genetics and environmental factors shared by cousins) and stronger in girls for ADHD and ASD, potentially indicating a differential influence of prenatal androgen exposure v. genetic factors. These results strengthen evidence for a potential causal influence of prenatal androgen exposure on the development of male-predominant neuropsychiatric disorders in female offspring of women with PCOS.

Interrogating the Genetic Determinants of Tourette's Syndrome and Other Tic Disorders Through Genome-Wide Association Studies

OBJECTIVE

Tourette's syndrome is polygenic and highly heritable. Genome-wide association study (GWAS) approaches are useful for interrogating the genetic architecture and determinants of Tourette's syndrome and other tic disorders. The authors conducted a GWAS meta-analysis and probed aggregated Tourette's syndrome polygenic risk to test whether Tourette's and related tic disorders have an underlying shared genetic etiology and whether Tourette's polygenic risk scores correlate with worst-ever tic severity and may represent a potential predictor of disease severity.

METHODS

GWAS meta-analysis, gene-based association, and genetic enrichment analyses were conducted in 4,819 Tourette's syndrome case subjects and 9,488 control subjects. Replication of top loci was conducted in an independent population-based sample (706 case subjects, 6,068 control subjects). Relationships between Tourette's polygenic risk scores (PRSs), other tic disorders, ascertainment, and tic severity were examined.

RESULTS

GWAS and gene-based analyses identified one genome-wide significant locus within FLT3 on chromosome 13, rs2504235, although this association was not replicated in the population-based sample. Genetic variants spanning evolutionarily conserved regions significantly explained 92.4% of Tourette's syndrome heritability. Tourette's-associated genes were significantly preferentially expressed in dorsolateral prefrontal cortex. Tourette's PRS significantly predicted both Tourette's syndrome and tic spectrum disorders status in the population-based sample. Tourette's PRS also significantly correlated with worst-ever tic severity and was higher in case subjects with a family history of tics than in simplex case subjects.

CONCLUSIONS

Modulation of gene expression through noncoding variants, particularly within cortico-striatal circuits, is implicated as a fundamental mechanism in Tourette's syndrome pathogenesis. At a genetic level, tic disorders represent a continuous spectrum of disease, supporting the unification of Tourette's syndrome and other tic disorders in future diagnostic schemata. Tourette's PRSs derived from sufficiently large samples may be useful in the future for predicting conversion of transient tics to chronic tic disorders, as well as tic persistence and lifetime tic severity.

Polygenic Risk Scores Derived From a Tourette Syndrome Genome-wide Association Study Predict Presence of Tics in the Avon Longitudinal Study of Parents and Children Cohort

BACKGROUND

Tourette syndrome (TS) has a well-established genetic background, but its genetic architecture remains largely unknown. The authors investigated the role of polygenic risk scores (PRSs) derived from a TS genome-wide association study in relation to the occurrence of tics and associated traits in a general population cohort.

METHODS

Using the most recent TS genome-wide association study (n = 4819 cases; n = 9488 controls) as the discovery sample, PRSs were calculated in Avon Longitudinal Study of Parents and Children participants (n = 8941). Regression analyses were used to assess whether PRS predicted the presence and chronicity of tics, and symptom severity of obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, and autism spectrum disorder in Avon Longitudinal Study of Parents and Children participants.

RESULTS

Following correction for multiple testing, the PRS significantly predicted the presence (R2 = .48%, p empirical = .01, Q = .04) but not the chronicity (R2 = .16%, p empirical = .07, Q = .14) of tics in the Avon Longitudinal Study of Parents and Children cohort; it did not predict the severity of obsessive-compulsive disorder (R2 = .11%, p empirical = .11, Q = .15), attention-deficit/hyperactivity disorder (R2 = .09%, p empirical = .19, Q = .21), or autism spectrum disorder (R2 = .12%, p empirical = .09, Q = .14).

CONCLUSIONS

The authors found a significant polygenic component of tics occurring in a general population cohort based on PRS derived from a genome-wide association study of individuals with a TS diagnosis. This finding supports the notion that tics along a spectrum from nonclinical to clinical symptom levels share a similar genetic background.

[Changes in T helper lymphocytes and their subsets in children with tic disorders]

OBJECTIVE

To explore the changes in T helper lymphocytes and their subsets in children with tic disorders (TD) and their clinical significance.

METHODS

Flow cytometry was used to measure the percentages of T helper lymphocytes and their subsets in the peripheral blood of children with TD and healthy children (controls).

RESULTS

The percentage of T helper lymphocytes was significantly lower in the TD group than in the control group (P<0.001). The abnormal rate of T helper lymphocytes in the TD group was significantly higher than that in the control group (68.7% vs 18.8%; P<0.001). The percentage of T helper lymphocytes was negatively correlated with Yale Global Tic Severity Scale score (r=-0.3945, P<0.001). As for the subsets of T helper lymphocytes, the TD group had a significantly higher percentage of Th1 cells and a significantly lower percentage of Th2 cells compared with the control group (P<0.001).

CONCLUSIONS

The abnormality of T helper lymphocytes and the imbalance of their subsets may be associated with the pathogenesis of TD in children. The percentage of T helper lymphocytes can be used as an indicator for assessing the severity of TD.

Modeling tics in rodents: Conceptual challenges and paths forward

BACKGROUND

Recent advances in our understanding of the neurobiology of tics have led to the development of novel rodent models capturing different pathophysiological and phenotypic aspects of Tourette syndrome. The proliferation of these models, however, raises vexing questions on what standards should be adopted to assess their theoretical validity and empirical utility. Assessing the homology of a rodent motoric burst with a tic remains problematic, due to our incomplete knowledge of the underpinnings of tics, their high phenotypic complexity and variability, limitations in our ability test key aspects of tic phenomenology (such as premonitory sensory phenomena) in animals, and between-species differences in neuroanatomy and behavioral repertoire. These limitations underscore that any interpretation of behavioral output in an animal model cannot exclusively rely on the recognition of features that bear superficial resemblance with tics, but must be supported by other etiological and convergent phenomenological criteria.

NEW METHOD

Here, we discuss two complementary approaches for the study and validation of tic-like manifestations in rodents, based respectively on the use of contextual modulators and accompanying features of repetitive motor manifestations and on the reproduction of pathogenic factors.

RESULTS

Neither strategy can by itself provide convincing evidence that a model informatively recapitulates tic pathophysiology. Their combination holds promise to enhance the rigorous evaluation and translational relevance of rodent models of tic disorders.

CONCLUSIONS

This systematic consideration of different approaches to the validation and study of animal models of tic pathophysiology provides a framework for future work in this area.

Heritability of tic disorders: a twin-family study

BACKGROUND

Genetic-epidemiological studies that estimate the contributions of genetic factors to variation in tic symptoms are scarce. We estimated the extent to which genetic and environmental influences contribute to tics, employing various phenotypic definitions ranging between mild and severe symptomatology, in a large population-based adult twin-family sample.

METHOD

In an extended twin-family design, we analysed lifetime tic data reported by adult mono- and dizygotic twins (n = 8323) and their family members (n = 7164; parents and siblings) from 7311 families in the Netherlands Twin Register. We measured tics by the abbreviated version of the Schedule for Tourette and Other Behavioral Syndromes. Heritability was estimated by genetic structural equation modeling for four tic disorder definitions: three dichotomous and one trichotomous phenotype, characterized by increasingly strictly defined criteria.

RESULTS

Prevalence rates of the different tic disorders in our sample varied between 0.3 and 4.5% depending on tic disorder definition. Tic frequencies decreased with increasing age. Heritability estimates varied between 0.25 and 0.37, depending on phenotypic definitions. None of the phenotypes showed evidence of assortative mating, effects of shared environment or non-additive genetic effects.

CONCLUSIONS

Heritabilities of mild and severe tic phenotypes were estimated to be moderate. Overlapping confidence intervals of the heritability estimates suggest overlapping genetic liabilities between the various tic phenotypes. The most lenient phenotype (defined only by tic characteristics, excluding criteria B, C and D of DSM-IV) rendered sufficiently reliable heritability estimates. These findings have implications in phenotypic definitions for future genetic studies.

[New impulses for tic research through international collaboration]

BACKGROUND

A section of the UMCG Child and Adolescent Psychiatry Department is currently focusing much of its research on tic disorders.

AIM

To provide an overview of the research projects on tic disorders being currently undertaken at our center.

METHOD

We discuss our research projects giving particular attention to factors that are restricting current research.

RESULTS

The first project is TIC Genetics, a project involving international collaboration. The researchers are looking for rare genetic variants in several family members who have tics and for new gene mutations in children who have tics but no family history of tics. TIC Genetics also investigates the interactions between genes and the environment. A second large-scale longitudinal project, the European Multicentre Tics in Children Study (EMTICS), is focusing on the interplay between genetics, auto-immunity, and environmental factors as a possible cause for the onset and exacerbation of tics. Finally, TS-EUROTRAIN is a European collaboration that concentrates on genetics, neuro-imaging and animal models.

CONCLUSION

International collaborations are essential if we are to acquire a deeper understanding of the etiology of tic disorders.

Animal models of tic disorders: a translational perspective

Tics are repetitive, sudden movements and/or vocalizations, typically enacted as maladaptive responses to intrusive premonitory urges. The most severe tic disorder, Tourette syndrome (TS), is a childhood-onset condition featuring multiple motor and at least one phonic tic for a duration longer than 1 year. The pharmacological treatment of TS is mainly based on antipsychotic agents; while these drugs are often effective in reducing tic severity and frequency, their therapeutic compliance is limited by serious motor and cognitive side effects. The identification of novel therapeutic targets and development of better treatments for tic disorders is conditional on the development of animal models with high translational validity. In addition, these experimental tools can prove extremely useful to test hypotheses on the etiology and neurobiological bases of TS and related conditions. In recent years, the translational value of these animal models has been enhanced, thanks to a significant re-organization of our conceptual framework of neuropsychiatric disorders, with a greater focus on endophenotypes and quantitative indices, rather than qualitative descriptors. Given the complex and multifactorial nature of TS and other tic disorders, the selection of animal models that can appropriately capture specific symptomatic aspects of these conditions can pose significant theoretical and methodological challenges. In this article, we will review the state of the art on the available animal models of tic disorders, based on genetic mutations, environmental interventions as well as pharmacological manipulations. Furthermore, we will outline emerging lines of translational research showing how some of these experimental preparations have led to significant progress in the identification of novel therapeutic targets for tic disorders.

Genetics of obsessive-compulsive disorder and related disorders

Twin and family studies support a significant genetic contribution to obsessive-compulsive disorder (OCD) and related disorders, such as chronic tic disorders, trichotillomania, skin-picking disorder, body dysmorphic disorder, and hoarding disorder. Recently, population-based studies and novel laboratory-based methods have confirmed substantial heritability in OCD. Genome-wide association studies and candidate gene association studies have provided information on specific gene variations that may be involved in the pathobiology of OCD, though a substantial portion of the genetic risk architecture remains unknown.

[Progress in research on susceptibility gene mapping of Tic disorder]

Tic disorder (TD) is a chronic neuropsychiatric disorder with childhood onset. Previous research has demonstrated that genetic factors play an important role in the pathogenesis of TD, and TD is a complex disease affected by multiple genes. Many susceptibility genes have been identified and the relationship between these genes and the etiology of TD was investigated in the past few years. These researches have yielded large valuable information as well as provided a reference for understanding the pathogenesis and further research of this disease. In this paper we reviewed the recent progress in the study on the susceptibility gene mapping of TD.

Obsessive-compulsive disorder: subclassification based on co-morbidity

BACKGROUND

Obsessive-compulsive disorder (OCD) is probably an etiologically heterogeneous condition. Many patients manifest other psychiatric syndromes. This study investigated the relationship between OCD and co-morbid conditions to identify subtypes.

METHOD

Seven hundred and six individuals with OCD were assessed in the OCD Collaborative Genetics Study (OCGS). Multi-level latent class analysis was conducted based on the presence of eight co-morbid psychiatric conditions [generalized anxiety disorder (GAD), major depression, panic disorder (PD), separation anxiety disorder (SAD), tics, mania, somatization disorders (Som) and grooming disorders (GrD)]. The relationship of the derived classes to specific clinical characteristics was investigated.

RESULTS

Two and three classes of OCD syndromes emerge from the analyses. The two-class solution describes lesser and greater co-morbidity classes and the more descriptive three-class solution is characterized by: (1) an OCD simplex class, in which major depressive disorder (MDD) is the most frequent additional disorder; (2) an OCD co-morbid tic-related class, in which tics are prominent and affective syndromes are considerably rarer; and (3) an OCD co-morbid affective-related class in which PD and affective syndromes are highly represented. The OCD co-morbid tic-related class is predominantly male and characterized by high conscientiousness. The OCD co-morbid affective-related class is predominantly female, has a young age at onset, obsessive-compulsive personality disorder (OCPD) features, high scores on the 'taboo' factor of OCD symptoms, and low conscientiousness.

CONCLUSIONS

OCD can be classified into three classes based on co-morbidity. Membership within a class is differentially associated with other clinical characteristics. These classes, if replicated, should have important implications for research and clinical endeavors.

Variants of the dopamine D2 receptor gene and risperidone-induced hyperprolactinemia in children and adolescents

OBJECTIVE

To investigate the association between hyperprolactinemia and variants of the dopamine D2 receptor (DRD2) gene in children and adolescents in long-term treatment with risperidone.

METHODS

Medically healthy 7 to 17-year-old patients chronically treated with risperidone but receiving no other antipsychotics were recruited in a cross-sectional study. Four DRD2 variants were genotyped and prolactin concentration was measured. Medication history was obtained from the medical records. The effect of the TaqIA variants of the DRD2 on the risk of risperidone-induced hyperprolactinemia was the primary outcome measure.

RESULTS

Hyperprolactinemia was present in 50% of 107 patients (87% males) treated with risperidone for an average of 2.9 years. Age, stage of sexual development, and the dose of risperidone independently predicted a higher prolactin concentration, whereas the dose of psychostimulants was negatively correlated with it. However, these four predictors became nonsignificant when risperidone serum concentration was entered into the model. Adverse events potentially related to hyperprolactinemia were more common in participants with elevated prolactin concentration and in girls (45%) compared with boys (10%). After controlling for risperidone concentration and the dose of psychostimulants, the TaqIA A1 and the A-241G alleles were associated with higher prolactin concentration, whereas the -141C Ins/Del and C957T variants had no significant effect. In addition, adverse events potentially related to hyperprolactinemia were four times more common in TaqIA A1 allele carriers.

CONCLUSION

Prolactin concentration is closely related to central DRD2 blockade, as reflected by risperidone serum concentration. Furthermore, the TaqIA and A-241G variants of the DRD2 gene could be useful in predicting the emergence of hyperprolactinemia and its potential adverse events.

Association of ADHD, tics, and anxiety with dopamine transporter (DAT1) genotype in autism spectrum disorder

BACKGROUND

Autism spectrum disorder (ASD) is associated with high rates of psychiatric disturbance to include attention-deficit/hyperactivity disorder (ADHD), tic disorder, and anxiety disorders. The aim of the present study was to examine the association between a variable number tandem repeat (VNTR) functional polymorphism located in the 3'-untranslated region of the dopamine transporter gene (DAT1) and the severity of these symptoms as well as the association between the DAT1 DdeI polymorphism and severity of tics.

METHODS

Parents (n = 62) and teachers (n = 57) completed a DSM-IV-referenced rating scale for 67 children with ASD.

RESULTS

According to parent ratings, children with the 10-10 repeat allele (versus a combined group of all other genotypes) exhibited less severe symptoms of hyperactivity and impulsivity as well as less severe language deficits. Teacher ratings indicated that social anxiety and tic symptoms were more severe for children with the 10-10 genotype versus all others. Exploratory analyses provided preliminary support for the notion that heterozygosity (9-10 repeat genotype) may be a risk/protective factor. There were no associations of tic severity with the DAT1 DdeI polymorphism.

CONCLUSION

Collectively, these results suggest that the extraordinary variability in ASD clinical phenotypes may be explained in part by the same genes that are implicated in a host of other psychiatric disorders in non-ASD populations. Nevertheless, replication with independent samples is necessary to confirm this preliminary finding.

Fragile X syndrome associated with tic disorders

Movement disorders other than late onset tremor-ataxia in association with fragile X syndrome, the most common identifiable cause of inherited mental retardation, seem to be rare. Here we describe five male patients from three unrelated families with fragile X syndrome that presented with motor and phonic tics. Clinically, 4 patients fulfilled diagnostic criteria for Gilles de la Tourette syndrome (GTS) while 1 patient would have been diagnosed with an adult onset tic disorder. However, in all patients onset of tics was considerably later than in typical GTS. Three patients had atypical tics and two patients reported waxing and waning of tic intensity over time. Four of the 5 patients showed clinical signs typical of fragile X syndrome, in particular dysmorphic features, learning difficulties and speech and language problems that required special treatment. All patients had co-morbidities common to both GTS and fragile X syndrome. We suggest considering fragile X syndrome in GTS complicated by co-morbidity with late onset of atypical tics, in particular when learning disability and dysmorphic features are present.

Candidate locus for chorea and tic disorders at 15q?

Cases of chromosomal aberrations are known to be associated with specific phenotypic abnormalities, including tics and chorea. We report the case of a 10-year-old caucasian boy with tics, chorea, and a de novo chromosome 15 paracentric inversion, 46,XY,inv(15) (q13;q22.3) identified with G-banding chromosome analysis (trypsin-Giemsa staining). Subsequent fluorescence in situ hybridization with locus-specific small nuclear ribonucleoprotein polypeptide N gene probe confirmed that the breakpoints of the inversion were distal to 15q12. Mutation analysis showed no mutation or polymorphism in the thyroid transcription factor 1 gene (TITF1). The results suggest that 15q is a region to explore for candidate genes of etiologic importance in the development of tics and chorea.

Association between the polymorphism in the promoter region of dopamine D4 receptor gene and chronic tic disorder

OBJECTIVE

To study a possible association between the three functional polymorphisms in the promoter region of dopamine D4 receptor (DRD4) gene and chronic tic disorder.

METHODS

Genomic DNA was isolated from the venous blood leukocytes of 84 unrelated patients with chronic tic disorder (Study group) and 100 healthy unrelated individuals (Control group). Polymorphisms of DRD4, 1240L/S, 616C/G and 521C/T, were genotyped by the allele-specific primer (ASP) PCR. Genotype, allele and haplotype frequencies were analysed by SHEsis online.

RESULTS

There were significant differences in both allele and genotype frequencies (chi(2) = 8.419, P < 0.01; chi(2) = 7.860, P < 0.05 respectively) of DRD4-616C/G between the Study and the Control groups. Haplotypic frequencies of LCT (1240L/S, 616C/G, 521C/T) in the Study group were noticeably higher than in the Control group (chi(2) = 6.371, P < 0.05).

CONCLUSIONS

There is an association between the DRD4-616C/G polymorphism and chronic tic disorder. The individuals with haplotype LCT (1240L/S, 616C/G, 521C/T) are susceptible to this disorder.

Psychopathology in tuberous sclerosis: an overview and findings in a population-based sample of adults with tuberous sclerosis

BACKGROUND

Tuberous sclerosis (TS) is a multi- system disorder with complex genetics. The neurodevelopmental manifestations of TS are responsible for considerable morbidity. The prevalence of epilepsy and intellectual disabilities among individuals with TS have been well described. Ours is the first study that explores the prevalence and pattern of psychopathology in a population-based sample of adults with TS.

METHODS

Sixty subjects were identified through a capture-recapture analysis of TS. Information was gathered as to seizure history, cognitive functioning (WISC-III) and psychopathology (SADS-L, SAPPA). Lifetime psychopathology was categorized according to Research Diagnostic Criteria. The overall pattern of mental illness (MI) was examined as well as how this varied with IQ and seizure history.

RESULTS

Twenty-four (40.0%) subjects had a history of MI. The most common diagnosis was that of an affective disorder [18 (30.0%)], the majority of which were major depressive episodes. Alcoholism [4 (6.7%)] and anxiety disorders [3 (5.0%)] were the next most common diagnoses. Two (3.3%) subjects had had a tic disorder. Only one individual had a diagnosis of schizophrenia. MI was found in 75.0% of those with a history of epilepsy and 37.5% of those without epilepsy. MI was significantly more prevalent in those with a full-scale IQ above 70.

CONCLUSIONS

A significant proportion of adult with TS experience MI. MI was significantly more [corrected] prevalent in subjects with a full-scale IQ above 70. Reasons for such a finding are explored, and related methodological considerations for future research outlined.

Tourette syndrome and other tic disorders in a total population of children: clinical assessment and background

AIM

To describe the symptoms, onset, heredity, pre-/perinatal events and socio-economic status in Tourette syndrome (TS) and other tic disorders.

METHODS

From a total population of 4479 children, 25 (0.6%) with TS, 58 (1.3%) with chronic motor/vocal tics (CMVT) and 214 (4.8%) with transient tics (TT) in the last year were found. A three-stage procedure was used: tic screening, telephone interview and clinical assessment. The TS group was compared with 25 children with TT and 25 controls without tics.

RESULTS

The mean age of the first symptoms of TS was significantly lower than the onset of CMVT. All except one with TS had contact with medical services. The tics of children with TS were significantly more severe than the tics of others. Younger age of onset of TS indicated more severe tics. Parents and siblings of children with TS had an increased prevalence of tic disorders, obsessive-compulsive behaviour (OCD), attention-deficit/hyperactivity disorder (ADHD) and depression. Eighty per cent had a first-degree relative with a psychiatric disorder. A non-significant increase with regards to reduced optimality score in the pre-, peri- or neonatal periods was found in children with TS compared to controls. No differences were found concerning socio-economic status.

CONCLUSION

Almost all children from a total population with TS have sought help from medical services. An increased prevalence of tics, OCD, depression or ADHD was found in the parents/siblings of children with TS, which draws attention to the importance of thorough investigation of family members.

A family study of early-onset obsessive-compulsive disorder

Results from family studies have suggested that obsessive-compulsive disorder (OCD) is a genetically heterogeneous disorder and have emphasized the importance of identifying valid subgroups of patients. The current study focused on early-onset OCD probands and examined the recurrence risks of OCD and tics among first-degree family members. One hundred six children and adolescents with OCD were recruited from a specialty clinic for OCD and 44 control individuals without OCD were identified by random-digit dialing. These 150 probands and their 465 first-degree relatives were assessed by trained interviewers, using standardized semi-structured interviews. Diagnoses were assigned according to DSM-IV criteria by two experts blind to the proband's diagnosis, through the best-estimate process. These data were analyzed using chi(2) tests, t-tests, logistic regression, and generalized estimating equations (GEE). Case probands had a mean age of onset of OC symptoms of 6.7 years (SD = 2.8), and high comorbid rates with Tourette syndrome (33%) and chronic tics (13.2%). Compared to control relatives, case relatives had higher age-corrected recurrence risks of OCD (22.7% vs. 0.9%, odds ratio (OR) = 32.5, 95% confidence interval (CI) = 4.5-230.8, P = 0.0005), and chronic tics (11.6% vs. 1.7%, OR = 7.9, 95% CI = 1.9-33.1, P = 0.005). A comorbid diagnosis of tics in the relatives was the best predictor of their diagnosis of OCD (OR = 7.35, 95% CI = 3.79-14.25, P < 0.0001). There was a significant correlation between the ages of onset of OCD in probands and their affected relatives. Childhood onset OCD is a highly familial disorder. Some early-onset cases may represent a valid subgroup, with higher genetic loading and shared vulnerability with chronic tic disorders.

Candidate locus for Gilles de la Tourette syndrome/obsessive compulsive disorder/chronic tic disorder at 18q22

Gilles de la Tourette syndrome (GTS), obsessive compulsive disorder (OCD), and chronic tic disorder (CTD) are chronic, potentially debilitating neuropsychiatric disorders that often cluster in families. Comorbidity data and family and linkage studies support the hypothesis that these phenotypes, in some cases, share a common etiology. Studies of chromosomal abnormalities associated with this phenotypic spectrum further show that GTS, OCD, and CTD may represent alternate manifestations of a shared genetic condition. We report on a 14-year-old girl with severe OCD and a t(2;18)(p12;q22) translocation. The patient's chromosome 18 breakpoint localizes to the same chromosomal band as two previously reported rearrangements associated with GTS, OCD, and CTD, and fine maps to a genomic position approximately 5 Mb from these rearrangements. The clustering of these three breakpoints within a relatively small genetic interval suggests that 18q22 is a promising region for containing a gene or genes of etiologic importance in the development of the GTS/OCD/CTD phenotypic spectrum.

Tics

PURPOSE OF REVIEW

This paper reviews the recent literature concerning Tourette syndrome and related disorders.

RECENT FINDINGS

Tourette syndrome is a common disorder in children and adolescents, with an established association with attention deficit hyperactivity disorder, obsessive compulsive disorder, and a number of other psychiatric disorders. Both autoimmune and genetic mechanisms are implicated in the pathophysiology of the syndrome, while neuroimaging studies have identified abnormalities in the composition of the basal ganglia and frontal lobe white matter, as well as alterations in dopaminergic activity. When necessary, treatment of tics can be successful with neuroleptics and alpha-2-adrenergic agonists. The use of stimulants in children with Tourette syndrome and comorbid attention deficit hyperactivity disorder does not appear to worsen tics.

SUMMARY

As a result of the recent literature, clinicians can feel comfortable treating children with co-morbid attention deficit hyperactivity disorder and Tourette syndrome with stimulant medications. It has also been established that transient tics are very common in children, and for the most part, non-disabling. In those children with persistent tics, behavioural disorders are associated which may impair success in school and psychosocial functioning. Clinicians have a number of therapeutic options, with recent double-blinded randomized trials of clonidine, risperidone, and desipramine showing benefit. Scientists continue to search for the cause of Tourette syndrome.

[Paroxysmal stereotypy-tic-dystonia syndrome]

CASE REPORTS

We report the cases of four males from four different families, who presented paroxysmal episodes from the 1st 2nd year. These episodes were characterised by asymmetrical bilateral dystonia of the upper limbs, predominantly in both hands, and were associated with orofacial dyskinesias, stereotipies (jumping, arm flapping, etc.), facial tics and, occasionally, phonic tics. Consciousness is not affected in any of the cases. These movements are triggered in situations where the patient is relaxed or excited. They occur daily and last from a few seconds to 30 minutes. Between the bouts, they remain asymptomatic. Family cases suggest it is inherited by autosomal dominant transmission, perhaps linked to the X chromosome; in addition, two cases are sporadic. In the only adult, the movements progress to a series of rhythmic bilateral dystonic myoclonias and facial tics dyskinesias. All the studies carried out, EEG, hemogram, biochemical analysis, neuroimaging, copper and ceruloplasmin levels, were normal.

CONCLUSIONS

1. We report a non epileptic paroxysmal disorder originating in the extrapyramidal tracts with its own characteristics, with onset during early childhood, which is associated with stereotipies, tics and dystonia; 2. It occurs predominantly in males; 3. It is inherited by autosomal dominant transmission, or perhaps sex linked autosomal dominant inheritance, and there are also sporadic cases; 4. The range of clinical features is very wide and includes cases in which there are few symptoms to others where the extent and gravity of the disorder is very significant.

Tic disorders in the adolescent

This chapter addresses the multidimensional nature of tic disorders. The several major dimensions include (1) duration of symptoms (from less than 1 year to lifelong); (2) intensity of symptoms (from mild to severe); (3) frequency of symptoms (from rare to constant); (4) variety of symptoms (from single motor group/single phonic tic to multiple occurrences of both types); (5) complexity of tics (from simple motor/phonic tics to tics involving multiple motor groups or the production of multiple sounds including involuntary phrases); (6) response to treatment (from good to minimal or no response); and (7) comorbid psychiatric disorders (from none to multiple). These dimensions and their relationship to a variety of tic disorder diagnoses are explored.

Anticipation of age at onset of obsessive-compulsive spectrum disorders in patients with obsessive-compulsive disorder

Anticipation of age at onset has been observed in several neuropsychiatric disorders. Recent studies have associated anticipation with the presence of unstable DNA and have suggested that trinucleotide repeats may be the main cause in some of these diseases. However, several selection biases may mimic the presence of such an effect. In this study we evaluated the presence of this effect in 40 families of probands with obsessive-compulsive disorder (OCD) compared with affected subjects in the parental generation. We controlled for ascertainment biases by taking into account the age at interview of probands. Using a different recruitment strategy, we controlled for anticipation in a sub-sample of offspring of 13 OCD patients, affected with OC spectrum disorders. While the younger generation showed a significantly earlier age at onset than the parental generation, no effect of age at interview was observed. Drawing on the results, we hypothesised that the presence of anticipation in OCD and OC spectrum disorders could be due to a specific genetic effect (unstable DNA), as it has been hypothesised for other disorders showing this effect.

[Transmission disequilibrium test of DRD4 exon III 48bp variant number tandem repeat polymorphism and tic disorder]

OBJECTIVE

To investigate whether DRD4 exon III48 bp variant number tandem repeat(VNTR) polymorphism is associated with tic disorder.

METHODS

One hundred and twenty-two nucleus families were collected using Structured clinical interview for genetic study of Tourette syndrome and related disorders for family-based association analysis of tic disorder and DRD4 exon III 48bp VNTR polymorphism. One hundred and twenty-two trios were divided into two groups: tic disorder group (82 trios of Tourette syndrome or chronic tic disorder, TS&CT) and tic disorder accompanied with attention deficit and hyperactivity disorder (ADHD) group (40 trios of Tourette syndrome or chronic tic disorder accompanied with ADHD, TS&ADHD). Transmission disequilibrium test (TDT), in addition to polymerase chain reaction and VNTR technique were conducted in 122 trios.

RESULTS

There exist 5 alleles at this polymorphic locus in this sample including DRD4 exon III 48bp 2-6 repeats. No transmission disequilibrium was found between DRD4 exon III 48 bp VNTR and tic disorder (chi square=7.44, P 0.12); however, when the sample was divided into two groups, transmission disequilibrium was noticed between the cases of TS&ADHD and this locus by overall allele-wise analysis (chi square=11.74, P 0.02), and there exists transmission disequilibrium exclusively between 5 or 6 repeats of 48bp VNTR(longer alleles) by allele-wise analysis (chi square=10.57, P 0.032, chi square=6.13, P 0.01). No transmission disequilibrium was seen between TS&CT and DRD4 exon III 48bp VNTR(chi square=3.38, P 0.50).

CONCLUSION

The results of this study have revealed an association between the longer alleles of DRD4 exon III 48bp VNTR polymorphism and tic disorder accompanied with ADHD, thus suggesting a possible genetic risk factor of tic disorder accompanied with ADHD in Chinese.

Tic disorders: when habit forming neural systems form habits of their own?

Tourette syndrome (TS), obsessive-compulsive disorder (OCD) and related conditions are prevalent disorders affecting as many as 0.3-3% of the population. They are frequently chronic and can be associated with marked impairment and disability. Although clinical care has improved over the past decade, a significant number of patients fail to respond adequately or experience intolerable side effects. The etiology of these disorders is unknown. Compelling evidence suggests that the vulnerability to develop TS and OCD is mediated by both genetic and environmental factors, and that neural systems located in the basal ganglia and functionally related brain structures are involved in their pathogenesis. Based on explicit models of pathogenesis for TS and OCD and building on work accomplished over the past two decades, an array of clinical, neuropsychological, genetic, neuroimaging, epidemiological neurobiological, and treatment studies have been completed or are underway at the Child Study Center at Yale University. A multidisciplinary team of investigators has joined forces to test specific hypotheses through the integration and translation of basic and clinical neuroscience research. All subjects have been studied using identical clinical, neuropsychological, genetic, neurobiological, and pharmacological techniques. Current conceptualizations of TS have been shaped by advances in clinical phenomenology, genetics, systems neuroscience and the emerging understanding of the role of the basal ganglia in implicit learning and habit formation, neuroimmunology and psychopharmacology. An appreciation of the premonitory urges that precede tics and temporal dynamics of tics have provided useful viewpoints from which to regard the natural history of TS. While the long-term outcome of TS can be relatively benign, the presence of comorbid conditions such as attention deficit/hyperactivity disorder (ADHD), OCD or a major affective disorder can have lasting untoward consequences. The identification of susceptibility genes in TS will doubtless point in new therapeutic directions for treatment, as will the characterization of the putative autoimmune mechanisms active in subgroup of patients. Continued success in functional in vivo neuroimaging studies will lead to the targeting of specific brain circuits for more intensive study. Although ideal anti-tic therapies are not available, recently completed clinical trials with alpha-adrenergic agents and atypical neuroleptics are encouraging. Given these developments, TS can be considered a model disorder to study the dynamic interplay of genetic vulnerabilities, epigenetic events, and neurobiological systems active during early brain development. It is likely that the research paradigms utilized in these studies and many of the empirical findings resulting from them, will be relevant to other disorders of childhood onset and to our understanding of normal development.

The familial phenotype of obsessive-compulsive disorder in relation to tic disorders: the Hopkins OCD family study

BACKGROUND

Obsessive-compulsive disorder (OCD) and tic disorders have phenomenological and familial-genetic overlaps. An OCD family study sample that excludes Tourette's syndrome in probands is used to examine whether tic disorders are part of the familial phenotype of OCD.

METHODS

Eighty case and 73 control probands and their first-degree relatives were examined by experienced clinicians using the Schedule for Affective Disorders and Schizophrenia-Lifetime Anxiety version. DSM-IV psychiatric diagnoses were ascertained by a best-estimate consensus procedure. The prevalence and severity of tic disorders, age-at-onset of OCD symptoms, and transmission of OCD and tic disorders by characteristics and type of proband (OCD + tic disorder, OCD - tic disorder) were examined in relatives.

RESULTS

Case probands and case relatives had a greater lifetime prevalence of tic disorders compared to control subjects. Tic disorders spanning a wide severity range were seen in case relatives; only mild severity was seen in control relatives. Younger age-at-onset of OCD symptoms and possibly male gender in case probands were associated with increased tic disorders in relatives. Although relatives of OCD + tic disorder and OCD - tic disorder probands had similar prevalences of tic disorders, this result is not conclusive.

CONCLUSIONS

Tic disorders constitute an alternate expression of the familial OCD phenotype.

Clinical and psychological features distinguishing obsessive-compulsive and chronic tic disorders

Medical and biogenetic research has suggested that obsessive-compulsive disorder and chronic (multiple) tic disorder may share a common etiology. This article reviews corresponding evidence for psychological similarities and differences between the two disorders. There are similarities in self-management strategies, psychological traits (both report high scores on different aspects of perfectionism) and in the ego-syntonic-ego-dystonic cycle of the impulsive-compulsive behavior. Situational cues likely to elicit or worsen the problem differ between the disorders as do associated emotions, comorbidity and background styles of action. In both disorders, cognitive factors, such as anticipations and appraisals of the problem, can play a role in onset and maintenance of the problem, and this raises the question as to whether cognitive or behavioral factors are best addressed in treatment. Psychological characteristics, such as lack of confidence, may contribute to apparent performance deficit. Psychological evaluation, particularly functional analysis, may aid in differential diagnosis between the two disorders, lead to improvement in treatment matching, and in understanding of the multidetermined etiology.

[Family study of genomic imprinting in tic disorder]

OBJECTIVE

To investigate whether genomic imprinting is involved in the etiology of tic disorder.

METHODS

International standard structural schedule for the genetic research of tic disorder and standard process of phenotype evaluation, in addition to both family study method and family history method were used in the family study of 171 probands with tic disorder.

RESULTS

Maternal transmission was associated with the symptom of complex motor tics in the probands (beta ratio = 6.6, P = 0.01); Maternal transmission was more likely to present earlier-onset of the disease (Log Rank = 4.71, P = 0.029); However, paternally transmitted tic disorder was characterized by increased attention problem score in CBCL behavioral scale among the proband (t = 2.78, chi(2) = 0.01).

CONCLUSION

Parental specific expression exists in the transmission of tic disorder, which gives evidence that genomic imprinting may be involved in the genetic mechanism of tic disorder.

Morbidity risk for obsessive-compulsive spectrum disorders in first-degree relatives of patients with eating disorders

OBJECTIVE

A hypothesis that eating disorders are a phenomenological variant of obsessive-compulsive disorder (OCD) has been proposed. This study was conducted to determine whether anorexia nervosa and bulimia, the two main eating disorders, are familial and whether the risk for obsessive-compulsive spectrum disorders (OCD and tic disorders) is higher in families of patients with eating disorders.

METHOD

The morbidity risk for obsessive-compulsive spectrum disorders in first-degree relatives of 136 female probands with eating disorders (84 with anorexia nervosa, 52 with bulimia) was compared to that for first-degree relatives of 72 female comparison subjects.

RESULTS

The morbidity risk for obsessive-compulsive spectrum disorders was significantly higher among the 436 relatives of the eating disorder probands than among the 358 relatives of the comparison subjects (9.69% versus 0%). This finding was independent of any comorbid diagnosis of an obsessive-compulsive spectrum disorder in the eating disorder probands. The eating disorder group and the comparison group did not differ in familial risk for eating disorders and tic disorders.

CONCLUSIONS

To better understand the genetic components of eating disorders, these disorders should be considered as part of the obsessive-compulsive spectrum of disorders.

Childhood-onset obsessive-compulsive disorder: a tic-related subtype of OCD?

Obsessive-compulsive disorder (OCD) is a psychiatric condition characterized by recurrent obsessions or compulsions that cause significant impairment or distress. Although OCD was once perceived to be relatively rare in childhood, current estimates suggest that as many as half of all adult OCD cases may have their onset in childhood or adolescence. In general, there appears to be a great deal of continuity between the clinical presentation of OCD in children and that in adults. Yet, numerous differences have also been found between child and adult OCD, including differences in sex distribution, patterns of comorbidity, and degree of familial loading. These differences raise the issue of whether obsessive-compulsive symptoms that have their onset in childhood, but perhaps persist into adult life, are meaningfully different from those that emerge de novo in adulthood. In this article, current research on child- and adult-onset OCD is critically reviewed. It is proposed that child-onset OCD represents a phenomenologically and etiologically distinct subtype of OCD, bearing a close genetic relationship to tic-disorders and possibly sharing a common or similar pathogenesis. Clinical implications of the child- versus adult-onset OCD distinction are discussed.

Significant linkage for Tourette syndrome in a large French Canadian family

Family and twin studies provide strong evidence that genetic factors are involved in the transmission of Gilles de la Tourette syndrome (TS) and related psychiatric disorders. To detect the underlying susceptibility gene(s) for TS, we performed linkage analysis in one large French Canadian family (127 members) from the Charlevoix region, in which 20 family members were definitely affected by TS and 20 others showed related tic disorders. Using model-based linkage analysis, we observed a LOD score of 3.24 on chromosome 11 (11q23). This result was obtained in a multipoint approach involving marker D11S1377, the marker for which significant linkage disequilibrium with TS recently has been detected in an Afrikaner population. Altogether, 25 markers were studied, and, for level of significance, we derived a criterion that took into account the multiple testing arising from the use of three phenotype definitions and three modes of inheritance, a procedure that yielded a LOD score of 3.18. Hence, even after adjustment for multiple testing, the present study shows statistically significant evidence for genetic linkage with TS.

Psychiatric disorders in first-degree relatives of children with pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS)

OBJECTIVE

To determine the rates of psychiatric disorders in the first-degree relatives of children with infection-triggered obsessive-compulsive disorder (OCD) and/or tics (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections; PANDAS).

METHOD

The probands of this study were 54 children with PANDAS (n = 24 with a primary diagnosis of OCD; n = 30 with a primary diagnosis of a tic disorder). One hundred fifty-seven first-degree relatives (100 parents [93%] and 57 siblings [100%]) were evaluated for the presence of a tic disorder. One hundred thirty-nine first-degree relatives (100 parents [93%] and 39 of 41 siblings over the age of 6 [95%]) were evaluated with clinical and structured psychiatric interviews to determine the presence of subclinical OCD, OCD, and other DSM-IV Axis I disorders.

RESULTS

Twenty-one probands (39%) had at least one first-degree relative with a history of a motor or vocal tic; 6 mothers (11%), 9 fathers (19%), and 8 siblings (16%) received this diagnosis. Fourteen probands (26%) had at least one first-degree relative with OCD; 10 mothers (19%), 5 fathers (11%), and 2 siblings (5%), received this diagnosis. An additional 8 parents (8%) and 3 siblings (8%) met criteria for subclinical OCD. Eleven parents (11%) had obsessive-compulsive personality disorder.

CONCLUSIONS

The rates of tic disorders and OCD in first-degree relatives of pediatric probands with PANDAS are higher than those reported in the general population and are similar to those reported previously for tic disorders and OCD. Further study is warranted to determine the nature of the relationship between genetic and environmental factors in PANDAS.

[Tic disease. Current genetic and neurochemical factors]

We review historical, conceptual, clinical and diagnostic criteria as well as present genetic and neurochemical factors of tic disorders. Epidemiologic data suggest that tic is an organic disease with autosomal dominant transmission. We emphasize immunohistochemical studies particularly related to the dopaminergic, noradrenergic and serotonergic systems. These modulate the activity of the cortico-striato-thalamocortical circuits implicated in both Tourette's syndrome and obsessive-compulsive disorder.

Investigation of dopamine system genes in obsessive-compulsive disorder

Evidence from anatomical, pharmacological, and animal studies on the involvement of the dopamine system in obsessive-compulsive disorder (OCD) is mounting. This, along with evidence for a genetic diathesis provided by family and twin studies, prompted us to conduct genetic association studies of dopamine system genes in OCD. We genotyped OCD patients (n > 100) and matched controls for four loci: (1) a 40-base-pair repeat in the dopamine transporter gene; (2) the TaqIA polymorphism and the serine/cysteine variation in the D2 dopamine receptor gene; (3) an MscI polymorphism in the D3 dopamine receptor gene; and (4) a 48-base-pair repeat in the D4 dopamine receptor gene. Significant differences in allele frequencies were found between patients and controls for the D4 receptor gene, although replication is required with family-based controls before any conclusions can be entertained. This study represents the first comprehensive assessment of the roles of dopamine system genes in OCD.

[A family study of obsessive-compulsive disorder]

OBJECTIVE

To explore the genetic etiology of obsessive-compulsive disorder (OCD) and genetic association between OCD and tic disorder.

METHODS

The mental disorders in the first degree and second degree relatives of 90 probands with OCD were investigated and compared with those of 100 healthy families by the method of family genetic study.

RESULTS

Compared to the control, the prevalence rates of schizophrenia, affective disorder, minor depression, subclinical OCD, general anxiety disorder and tic disorder in the first degree relatives of OCD were elevated, except that of OCD. The prevalence rates of OCD and subclinical OCD, general anxiety disorder, and other neurotic disorders in the first degree relatives of patients with pure obsession were 47.6%, 35.7% and 23.8%, respectively; compared to 10.8%, 3.6% and 0 in those of the control (P<0.01). The prevalence rates of schizophrenia,affective disorder,and tic disorder in the first degree relatives of OCD with tic were 52.0%, 26.0% and 90.9%, respectively; compared to 0, 3.6% and 7.2% in those of the control (P<0.01).

CONCLUSION

The etiology of OCD is related to heredity. There was evidence to show genetic association between OCD and tic disorder,The elevation of prevalence rates of various mental disorders in the first degree relatives of OCD might suggest the genetic basis of various subtypes of OCD.

Neuropsychiatric disorders

Neuropsychiatric disorders of childhood include autism spectrum disorders, disorders comprising attention deficits (attention-deficit-hyperactivity disorder and deficits in attention, motor control and perception), tics (motor or vocal, or both), and obsessions and compulsions (obsessive-compulsive disorder). They affect a small proportion of the child population. They can now reliably be diagnosed, and are valid and clinically meaningful conditions. Effective interventions are available for most of these disorders.

Autism, affective and other psychiatric disorders: patterns of familial aggregation

BACKGROUND

The liability to autism confers a risk for a range of more subtle autistic-like impairments, but it remains unclear whether it also confers a risk for other psychiatric disturbances.

METHODS

To investigate this, we studied the pattern of familial aggregation of psychiatric disorders in relatives of 99 autistic and 36 Down's probands, using family history and direct interview measures.

RESULTS

Family history data showed that motor tics, obsessive-compulsive (OCD) and affective disorders were significantly more common in relatives of autistic probands and that individuals with OCD were more likely to exhibit autistic-like social and communication impairments. Direct interview data confirmed the increased rate of affective disorders (especially major depressive disorder) in the first-degree relatives. There was no evidence to indicate significant co-morbidity between affective disorders and the broadly defined phenotype of autism. Moreover, the characteristics of the probands' and the relatives' that were associated with the liability to familiarity of the broader phenotype of autism differed from those that predicted the liability to the familiarity of affective disorders. Examination of the onset of affective disorders suggested that the increased risk was not confined to the period following the birth of the child with autism.

CONCLUSIONS

Overall, the results indicated that OCD, but not affective disorders, may index an underlying liability to autism. They also indicated that the increased risk of affective disorders was not solely the consequence of the stress of raising a child with autism and that further research will be required to clarify the mechanisms involved.

Increased prevalence of the seven-repeat variant of the dopamine D4 receptor gene in patients with obsessive-compulsive disorder with tics

The polymorphism characterized by a varying number of 48 bp repeats (VNTR) in the dopamine D4 receptor (DRD4) gene was examined in 61 obsessive-compulsive disorder (OCD) probands with and without tics. Most of the OCD patients with tics showed at least one copy of the 7-fold variant compared to those affected subjects without tics (91 vs. 48%, respectively, Yates corrected chi2 = 5.54, P = 0.018). Similarly, a higher number of copies of this common variant were detected in the group of probands displaying tics compared to those OCD's without tics (Yates corrected chi2 = 4.66, P = 0.03). Our study suggests that the seven-repeat allele of the DRD4 gene could be a factor in the phenotypic variance of tics among OCD individuals.

Linkage study of the dopamine D5 receptor gene and Gilles de la Tourette syndrome

A defect in the dopamine system has been hypothesized as the etiological defect in Gilles de la Tourette syndrome (TS). In this report, we test the hypothesis that the dopamine D5 receptor locus (DRD5) is linked to the genetic susceptibility to TS in five families studied in Canada. We tested for linkage to the dopamine D5 receptor gene using a microsatellite polymorphism located in the same cosmid clone. Using an autosomal dominant model with reduced penetrance, we were able to exclude linkage in four of the five families for the TS and chronic multiple tics (CMT) phenotype. Also, no evidence for linkage was found using nonparametric methods in all five families.

Linkage disequilibrium between an allele at the dopamine D4 receptor locus and Tourette syndrome, by the transmission-disequilibrium test

Dopaminergic abnormalities are implicated in the pathogenesis of Tourette syndrome (TS) and chronic multiple tics. We used the transmission-disequilibrium test (TDT) method to test for linkage disequilibrium between a specific allele (the seven-repeat allele (DRD4*7R) of the exon 3 VNTR polymorphic site) at the D4 dopamine receptor locus (DRD4) and expression of chronic multiple tics and TS. This particular allele had been shown in functional studies to have different binding properties compared with the other common alleles in this DRD4 polymorphic system. We studied 64 family trios (consisting of an affected person and two parents, at least one heterozygous for DRD4*7R), including 12 nuclear family trios and 52 trios from four large TS kindreds. The DRD4*7R allele was transmitted significantly more frequently than expected (chi 2 TDT ranging from 8.47 [P < .004] to 10.80 [P = .001], depending on breadth of disease definition and inclusion or exclusion of inferred genotypes). Confirmation of this finding will depend on either replication in other samples or the identification of a transmitted functional mutation within this sample.