Skip to main content Accessibility help
×
Home
Hostname: page-component-5bf98f6d76-slc4r Total loading time: 9.031 Render date: 2021-04-21T08:01:31.657Z Has data issue: true Feature Flags: { "shouldUseShareProductTool": true, "shouldUseHypothesis": true, "isUnsiloEnabled": true, "metricsAbstractViews": false, "figures": false, "newCiteModal": false, "newCitedByModal": true }

Heritability of tic disorders: a twin-family study

Published online by Cambridge University Press:  15 December 2016

N. R. Zilhão
Affiliation:
Department of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands Department of Clinical Psychology, Utrecht University, The Netherlands
M. C. Olthof
Affiliation:
Department of Psychology, University of Amsterdam, The Netherlands
D. J. A. Smit
Affiliation:
Department of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands Department of Psychiatry, Academic Medical Center, Amsterdam, The Netherlands
D. C. Cath
Affiliation:
Department of Clinical Psychology, Utrecht University, The Netherlands Altrecht Academic Anxiety Center, Utrecht, The Netherlands
L. Ligthart
Affiliation:
Department of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands
C. A. Mathews
Affiliation:
Department of Psychiatry, University of Florida, Gainesville, FL, USA
K. Delucchi
Affiliation:
Department of Psychiatry, University of California, San Francisco, CA, USA
D. I. Boomsma
Affiliation:
Department of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands
C. V. Dolan
Affiliation:
Department of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands
Corresponding

Abstract

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.

Type
Original Articles
Copyright
Copyright © Cambridge University Press 2016 

Access options

Get access to the full version of this content by using one of the access options below.

Footnotes

† Both authors contributed equally to this work.

References

American Psychiatric Association (1994). Diagnostic and Statistical Manual of Mental Disorders, 4th edn. American Psychiatric Association: Washington, DC.Google ScholarPubMed
American Psychiatric Association (2000). Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision, 4th edn. American Psychiatric Association: Washington, DC.Google ScholarPubMed
Anckarsäter, H, Lundström, S, Kollberg, L, Kerekes, N, Palm, C, Carlström, E, Långström, N, Magnusson P, K, Halldner, L, Bölte, S, Gillberg, C, Gumpert, C, Råstam, M, Lichtenstein, P (2011). The Child and Adolescent Twin Study in Sweden (CATSS). Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies 14, 495508.CrossRefGoogle Scholar
Anonymous (1993). Definitions and classification of tic disorders. The Tourette Syndrome Classification Study Group. Archives of Neurology 50, 10131016.CrossRefGoogle ScholarPubMed
Apter, A, Pauls, DL, Bleich, A, Zohar, AH, Kron, S, Ratzoni, G, Dycian, A, Kotler, M, Weizman, A, Gadot, N, Cohen, DJ (1993). An epidemiologic study of Gilles de la Tourette's syndrome in Israel. Archives of General Psychiatry 50, 734738.CrossRefGoogle ScholarPubMed
Bar-Dayan, Y, Arnson, Y, Elishkevits, K (2010). Screening for common neurologic diseases among Israeli adolescents. Journal of Child Neurology 25, 348351.CrossRefGoogle ScholarPubMed
Bloch, MH, Leckman, JF (2009). Clinical course of Tourette syndrome. Journal of Psychosomatic Research 67, 497501.CrossRefGoogle ScholarPubMed
Boker, S, Neale, M, Maes, H, Wilde, M, Spiegel, M, Brick, T, Spies, J, Estabrook, R, Kenny, S, Bates, T, Mehta, P, Fox, J (2011). OpenMx: an open source extended structural equation modeling framework. Psychometrika 76, 306317.CrossRefGoogle ScholarPubMed
Bolton, D, Rijsdijk, F, O'Connor, TG, Perrin, S, Eley, TC (2007). Obsessive–compulsive disorder, tics and anxiety in 6-year-old twins. Psychological Medicine 37, 3948.CrossRefGoogle ScholarPubMed
Cath, DC, Hedderly, T, Ludolph, AG, Stern, JS, Murphy, T, Hartmann, A, Czernecki, V, Robertson, MM, Martino, D, Munchau, A, Rizzo, R; ESSTS Guidelines Group (2011). European clinical guidelines for Tourette syndrome and other tic disorders. Part I: assessment. European Child and Adolescent Psychiatry 20, 155171.CrossRefGoogle ScholarPubMed
Cubo, E, Gabriel y Galán, JM, Villaverde, VA, Velasco, SS, Benito, VD, Macarrón, JV, Guevara, JC, Louis, ED, Benito-León, J (2011). Prevalence of tics in schoolchildren in central Spain: a population-based study. Pediatric Neurology 45, 100108.CrossRefGoogle ScholarPubMed
Davis, LK, Yu, D, Keenan, CL, Gamazon, ER, Konkashbaev, AI, Derks, EM, Neale, BM, Yang, J, Lee, SH, Evans, P, Barr, CL, Bellodi, L, Benarroch, F, Berrio, GB, Bienvenu, OJ, Bloch, MH, Blom, RM, Bruun, RD, Budman, CL, Camarena, B, Campbell, D, Cappi, C, Cardona Silgado, JC, Cath, DC, Cavallini, MC, Chavira, DA, Chouinard, S, Conti, DV, Cook, EH, Coric, V, Cullen, BA, Deforce, D, Delorme, R, Dion, Y, Edlund, CK, Egberts, K, Falkai, P, Fernandez, TV, Gallagher, PJ, Garrido, H, Geller, D, Girard, SL, Grabe, HJ, Grados, MA, Greenberg, BD, Gross-Tsur, V, Haddad, S, Heiman, GA, Hemmings, SM, Hounie, AG, Illmann, C, Jankovic, J, Jenike, MA, Kennedy, JL, King, RA, Kremeyer, B, Kurlan, R, Lanzagorta, N, Leboyer, M, Leckman, JF, Lennertz, L, Liu, C, Lochner, C, Lowe, TL, Macciardi, F, McCracken, JT, McGrath, LM, Mesa Restrepo, SC, Moessner, R, Morgan, J, Muller, H, Murphy, DL, Naarden, AL, Ochoa, WC, Ophoff, RA, Osiecki, L, Pakstis, AJ, Pato, MT, Pato, CN, Piacentini, J, Pittenger, C, Pollak, Y, Rauch, SL, Renner, TJ, Reus, VI, Richter, MA, Riddle, MA, Robertson, MM, Romero, R, Rosàrio, MC, Rosenberg, D, Rouleau, GA, Ruhrmann, S, Ruiz-Linares, A, Sampaio, AS, Samuels, J, Sandor, P, Sheppard, B, Singer, HS, Smit, JH, Stein, DJ, Strengman, E, Tischfield, JA, Valencia Duarte, AV, Vallada, H, Van Nieuwerburgh, F, Veenstra-Vanderweele, J, Walitza, S, Wang, Y, Wendland, JR, Westenberg, HG, Shugart, YY, Miguel, EC, McMahon, W, Wagner, M, Nicolini, H, Posthuma, D, Hanna, GL, Heutink, P, Denys, D, Arnold, PD, Oostra, BA, Nestadt, G, Freimer, NB, Pauls, DL, Wray, NR, Stewart, SE, Mathews, CA, Knowles, JA, Cox, NJ, Scharf, JM (2013). Partitioning the heritability of Tourette syndrome and obsessive compulsive disorder reveals differences in genetic architecture. PLoS Genetics 9, e1003864 CrossRefGoogle ScholarPubMed
de Haan, MJ, Delucchi, KL, Mathews, CM, Cath, DC (2015). Tic symptom dimensions and their heritabilities in Tourette's syndrome. Psychiatric Genetics 25, 112118.CrossRefGoogle ScholarPubMed
Dobson, AJ, Barnett, A (2008). An Introduction to Generalized Linear Models, 3rd edn. Chapman and Hall/CRC: London.Google Scholar
Eapen, V, Laker, M, Anfield, A, Dobbs, J, Robertson, MM (2001). Prevalence of tics and Tourette syndrome in an inpatient adult psychiatry setting. Journal of Psychiatry and Neuroscience: JPN 26, 417420.Google Scholar
Erenberg, G, Cruse, R, Rothner, A (1987). The natural history of Tourette syndrome: a follow-up study. Annals of Neurology 22, 383385.CrossRefGoogle ScholarPubMed
Falconer, DS (1965). The inheritance of liability to certain diseases, estimated from the incidence among relatives. Annals of Human Genetics 29, 5176.CrossRefGoogle Scholar
Falconer, DS (1967). The inheritance of liability to diseases with variable age of onset, with particular reference to diabetes mellitus. Annals of Human Genetics 31, 120.CrossRefGoogle Scholar
Felling, RJ, Singer, HS (2011). Neurobiology of Tourette syndrome: current status and need for further investigation. Journal of Neuroscience 31, 1238712395.CrossRefGoogle ScholarPubMed
Findley, DB, Leckman, JF, Katsovich, L, Lin, H, Zhang, H, Grantz, H, Otka, J, Lombroso, PJ, King, RA (2003). Development of the Yale Children's Global Stress Index (YCGSI) and its application in children and adolescents with Tourette's syndrome and obsessive–compulsive disorder. Journal of the American Academy of Child and Adolescent Psychiatry 42, 450457.CrossRefGoogle Scholar
Freeman, RD, Fast, DK, Burd, L, Kerbeshian, J, Robertson, MM, Sandor, P (2000). An international perspective on Tourette syndrome: selected findings from 3,500 individuals in 22 countries. Developmental Medicine and Child Neurology 42, 436447.CrossRefGoogle ScholarPubMed
Hanna, PA, Janjua, FN, Contant, CF, Jankovic, J (1999). Bilineal transmission in Tourette syndrome. Neurology 11, 813818.CrossRefGoogle Scholar
Hansson, SL, Svanström Röjvall, A, Rastam, M, Gillberg, C, Gillberg, C, Anckarsäter, H (2005). Psychiatric telephone interview with parents for screening of childhood autism – tics, attention-deficit hyperactivity disorder and other comorbidities (A-TAC): preliminary reliability and validity. British Journal of Psychiatry 187, 262267.CrossRefGoogle ScholarPubMed
Hasstedt, SJ, Leppert, M, Filloux, F, van de Wetering, BJ, McMahon, WM (1995). Intermediate inheritance of Tourette syndrome, assuming assortative mating. American Journal of Human Genetics 57, 682689.Google ScholarPubMed
Hettema, JM, Neale, MC, Kendler, KS (2001). A review and meta-analysis of the genetic epidemiology of anxiety disorders. American Journal of Psychiatry 158, 15681578.CrossRefGoogle ScholarPubMed
Hirschtritt, ME, Lee, PC, Pauls, DL, Dion, Y, Grados, MA, Illmann, C, King, RA, Sandor, P, McMahon, WM, Lyon, GJ, Cath, DC, Kurlan, R, Robertson, MM, Osiecki, L, Scharf, JM, Mathews, CA; Tourette Syndrome Association International Consortium for Genetics (2015). Lifetime prevalence, age of risk, and genetic relationships of comorbid psychiatric disorders in Tourette syndrome. JAMA Psychiatry 72, 325333.CrossRefGoogle ScholarPubMed
Hirtz, D, Thurman, DJ, Gwinn-Hardy, K, Mohamed, M, Chaudhuri, AR, Zalutsky, R (2007). How common are the “common” neurologic disorders? Neurology 68, 326337.CrossRefGoogle ScholarPubMed
Khalifa, N (2006). Psychopathology in a Swedish population of school children with tic disorders. Journal of the American Academy of Child and Adolescent Psychiatry 45, 13461353.CrossRefGoogle Scholar
Knight, T, Steeves, T, Day, L, Lowerison, M, Jette, N, Pringsheim, T (2012). Prevalence of tic disorders: a systematic review and meta-analysis. Pediatric Neurology 47, 7790.CrossRefGoogle Scholar
Kraft, JT, Dalsgaard, S, Obel, C, Thomsen, PH, Henriksen, TB, Scahill, L (2012). Prevalence and clinical correlates of tic disorders in a community sample of school-age children. European Child and Adolescent Psychiatry 21, 513.CrossRefGoogle Scholar
Kurlan, R, Eapen, V, Stern, J, McDermott, MP, Robertson, MM (1994). Bilineal transmission in Tourette's syndrome families. Neurology 44, 23362342.CrossRefGoogle ScholarPubMed
Kurlan, R, McDermott, MP, Deeley, C, Como, PG, Brower, C, Eapen, S, Andresen, EM, Miller, B (2001). Prevalence of tics in schoolchildren and association with placement in special education. Neurology 57, 13831388.CrossRefGoogle ScholarPubMed
Larson, T, Anckarsäter, H, Gillberg, C, Ståhlberg, O, Carlström, E, Kadesjö, B, Råstam, M, Lichtenstein, P, Gillberg, C (2010). The Autism – Tics, AD/HD and other Comorbidities inventory (A-TAC): further validation of a telephone interview for epidemiological research. BMC Psychiatry 10, 1.CrossRefGoogle ScholarPubMed
Lichtenstein, P, Carlström, E, Råstam, M, Gillberg, C, Anckarsäter, H (2010). The genetics of autism spectrum disorders and related neuropsychiatric disorders in childhood. American Journal of Psychiatry 167, 13571363.CrossRefGoogle ScholarPubMed
Mataix-Cols, D, Isomura, K, Pérez-Vigil, A, Chang, Z, Rück, C, Larsson, KJ, Leckman, JF, Serlachius, E, Larsson, H, Lichtenstein, P (2015). Familial risks of Tourette syndrome and chronic tic disorders. A population-based cohort study. JAMA Psychiatry 72, 787–793.CrossRefGoogle ScholarPubMed
Mathews, CA, Grados, MA (2011). Familiality of Tourette syndrome, obsessive–compulsive disorder, and attention-deficit/hyperactivity disorder: heritability analysis in a large sib–pair sample. Journal of the American Academy of Child and Adolescent Psychiatry 50, 4654.CrossRefGoogle Scholar
Mathews, CA, Scharf, JM, Miller, LL, Macdonald-Wallis, C, Lawlor, DA, Ben-Shlomo, Y (2014). Association between pre- and perinatal exposures and Tourette syndrome or chronic tic disorder in the ALSPAC cohort. British Journal of Psychiatry 204, 4045.CrossRefGoogle ScholarPubMed
McMahon, WM, van de Wetering, BJ, Filloux, F, Betit, K, Coon, H, Leppert, M (1996). Bilineal transmission and phenotypic variation of Tourette's disorder in a large pedigree. Journal of the American Academy of Child and Adolescent Psychiatry 35, 672680.CrossRefGoogle Scholar
Miller, LL, Scharf, JM, Mathews, CA, Ben-Shlomo, Y (2014). Tourette syndrome and chronic tic disorder are associated with lower socio-economic status: findings from the Avon Longitudinal Study of Parents and Children cohort. Developmental Medicine and Child Neurology 56, 157163.CrossRefGoogle ScholarPubMed
Ooki, S (2005). Genetic and environmental influences on stuttering and tics in Japanese twin children. Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies 8, 6975.CrossRefGoogle ScholarPubMed
Pauls, D, Hurst, C (1996). Schedule for Tourette and Other Behavioural Syndromes. The Yale Family/Genetic Study Self-Report Questionnaire for Tics, Obsessive–Compulsiveness, Attentional Difficulties, Impulsivity and Motor Hyperactivity . Child Study Center, Yale University School of Medicine: New Haven, CT.Google Scholar
Pauls, DL (2010). The genetics of obsessive–compulsive disorder: a review. Dialogues in Clinical Neuroscience 12, 149163.Google ScholarPubMed
Pauls, DL, Raymond, CL, Stevenson, JM, Leckman, JF (1991). A family study of Gilles de la Tourette syndrome. American Journal of Human Genetics 48, 154163.Google ScholarPubMed
Pinto, R, Monzani, B, Leckman, JF, Rück, C, Serlachius, E, Lichtenstein, P, Mataix-Cols, D (2016). Understanding the covariation of tics, attention-deficit/hyperactivity, and obsessive–compulsive symptoms: a population-based adult twin study. American Journal of Medical Genetics. Part B, Neuropsychiatric Genetics 171, 938947.CrossRefGoogle ScholarPubMed
Posthuma, D, Boomsma, DI (2000). A note on the statistical power in extended twin designs. Behavior Genetics 30, 147158.CrossRefGoogle ScholarPubMed
Price, RA, Kidd, KK, Cohen, DJ, Pauls, DL, Leckman, JF (1985). A twin study of Tourette syndrome. Archives of General Psychiatry 42, 815820.CrossRefGoogle ScholarPubMed
Rietveld, MJ, van Der Valk, JC, Bongers, IL, Stroet, TM, Slagboom, PE, Boomsma, DI (2000). Zygosity diagnosis in young twins by parental report. Twin Research: The Official Journal of the International Society for Twin Studies 3, 134141.CrossRefGoogle ScholarPubMed
Robertson, MM, Eapen, V, Cavanna, AE (2009). The international prevalence, epidemiology, and clinical phenomenology of Tourette syndrome: a cross-cultural perspective. Journal of Psychosomatic Research 67, 475483.CrossRefGoogle ScholarPubMed
Robertson, MM, Verril, M, Mercer, M, James, B, Pauls, DL (1994). Tourette's syndrome in New Zealand. A postal survey. British Journal of Psychiatry: The Journal of Mental Science 164, 263266.CrossRefGoogle ScholarPubMed
Sabb, FW, Burggren, AC, Higier, RG, Fox, J, He, J, Parker, DS, Poldrack, RA, Chu, W, Cannon, TD, Freimer, NB, Bilder, RM (2009). Challenges in phenotype definition in the whole-genome era: multivariate models of memory and intelligence. Neuroscience 164, 88107.CrossRefGoogle ScholarPubMed
Scahill, L, Dalsgaard, S, Bradbury, K (2013). The prevalence of Tourette syndrome and its relationship to clinical features. In Tourette Syndrome (ed. Martino, D and Leckman, JF), pp. 121133. Oxford University Press: Oxford.CrossRefGoogle ScholarPubMed
Scahill, L, Sukhodolsky, DG, Williams, SK, Leckman, JF (2005). Public health significance of tic disorders in children and adolescents. Advances in Neurology 96, 240248.Google ScholarPubMed
Scahill, L, Williams, S, Schwab-Stone, M, Applegate, J, Leckman, JF (2006). Disruptive behavior problems in a community sample of children with tic disorders. Advances in Neurology 99, 184190.Google Scholar
Schlander, M, Schwarz, O, Rothenberger, A, Roessner, V (2011). Tic disorders: administrative prevalence and co-occurrence with attention-deficit/hyperactivity disorder in a German community sample. European Psychiatry: The Journal of the Association of European Psychiatrists 26, 370374.CrossRefGoogle Scholar
Shimada-Sugimoto, M, Otowa, T, Hettema, JM (2015). Genetics of anxiety disorders: genetic epidemiological and molecular studies in humans. Psychiatry and Clinical Neurosciences 69, 388401.CrossRefGoogle ScholarPubMed
Smith, S, Hay El, H, Farhat, N, Rekaya, R (2013). Genome wide association studies in presence of misclassified binary responses. BMC Genetics 14, 124.CrossRefGoogle ScholarPubMed
Swain, JE, Leckman, JF (2005). Tourette syndrome and tic disorders. Psychiatry (Edgmont) 2, 2636.Google ScholarPubMed
van Grootheest, D, Bartels, M, Cath, DC, Beekman, AT, Hudziak, JJ, Boomsma, DI (2007). Genetic and environmental influences on obsessive–compulsive symptoms in adults: a population-based twin-family study. Psychological Medicine 37, 16351644.CrossRefGoogle ScholarPubMed
van Grootheest, DS, Cath, DC, Beekman, AT, Boomsma, DI (2005). Twin studies on obsessive–compulsive disorder: a review. Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies 8, 450458.CrossRefGoogle ScholarPubMed
Walkup, JT, Ferrao, Y, Leckman, JF, Stein, DJ, Singer, H (2010). Tic disorders: some key issues for DSM-V. Depression and Anxiety 27, 600610.CrossRefGoogle ScholarPubMed
Wenning, GK, Kiechl, S, Seppi, K, Müller, J, Högl, B, Saletu, M, Rungger, G, Gasperi, A, Willeit, J, Poewe, W (2005). Prevalence of movement disorders in men and women aged 50–89 years (Bruneck Study cohort): a population-based study. Lancet Neurology 4, 815820.CrossRefGoogle ScholarPubMed
Willemsen, G, Vink, JM, Abdellaoui, A, den Braber, A, van Beek, JHDA, Draisma, HHM, van Dongen, J, van ‘t Ent, D, Geels, LM, van Lien, R, Ligthart, L, Kattenberg, M, Mbarek, H, de Moor, MHM, Neijts, M, Pool, R, Stroo, N, Kluft, C, Suchiman, HED, Slagboom, PE, de Geus, EJC, Boomsma, DI (2013). The Adult Netherlands Twin Register: twenty-five years of survey and biological data collection. Twin Research and Human Genetics: The Official Journal of the International Society for Twin Studies 16, 271281.CrossRefGoogle ScholarPubMed
Wray, NR, Lee, SH, Kendler, KS (2012). Impact of diagnostic misclassification on estimation of genetic correlations using genome-wide genotypes. European Journal of Human Genetics 20, 668674.CrossRefGoogle ScholarPubMed
Wray, NR, Maier, R (2014). Genetic basis of complex genetic disease: the contribution of disease heterogeneity to missing heritability. Current Epidemiology Reports 1, 220227.CrossRefGoogle Scholar
Yang, J, Lee, SH, Goddard, ME, Visscher, PM (2011). GCTA: a tool for genome-wide complex trait analysis. American Journal of Human Genetics 88, 7682.CrossRefGoogle ScholarPubMed
Zilhão, NR, Smit, DJ, Den Braber, A, Dolan, CV, Willemsen, G, Boomsma, DI, Cath, DC (2014). Genetic and environmental contributions to stability in adult obsessive compulsive behavior. Twin Research and Human Genetics 18, 5260.CrossRefGoogle ScholarPubMed
Zohar, AH, Ratzoni, G, Pauls, DL, Apter, A, Bleich, A, Kron, S, Rappaport, M, Weizman, A, Cohen, DJ (1992). An epidemiological study of obsessive–compulsive disorder and related disorders in Israeli adolescents. Journal of the American Academy of Child and Adolescent Psychiatry 31, 10571061.CrossRefGoogle ScholarPubMed

Zilhão supplementary material

Figures S1-S3 and Tables S1-S5

File 281 KB

Altmetric attention score

Full text views

Full text views reflects PDF downloads, PDFs sent to Google Drive, Dropbox and Kindle and HTML full text views.

Total number of HTML views: 44
Total number of PDF views: 238 *
View data table for this chart

* Views captured on Cambridge Core between 15th December 2016 - 21st April 2021. This data will be updated every 24 hours.

Send article to Kindle

To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about sending to your Kindle.

Note you can select to send to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Heritability of tic disorders: a twin-family study
Available formats
×

Send article to Dropbox

To send this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Dropbox.

Heritability of tic disorders: a twin-family study
Available formats
×

Send article to Google Drive

To send this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your <service> account. Find out more about sending content to Google Drive.

Heritability of tic disorders: a twin-family study
Available formats
×
×

Reply to: Submit a response


Your details


Conflicting interests

Do you have any conflicting interests? *