Reliability and Validity of the Yale Global Tic Severity Scale

Reliability and Validity of the Yale Global Tic Severity Scale
[BRIEF REPORT]
Storch, Eric A.1,3,4; Murphy, Tanya K.3; Geffken, Gary R.3; Sajid, Muhammad3; Allen, Pam3; Roberti, Jonathan W.2; Goodman, Wayne K.3
1Department of Pediatrics, University of Florida
2Department of Psychology, New College of Florida
3Department of Psychiatry, University of Florida.
4Correspondence concerning this article should be addressed to Eric A. Storch, Department of Psychiatry, University of Florida, Box 100234, Gainesville, FL 32610. E-mail estorch@psychiatry.ufl.edu.
This research was funded by grants from the National Institute of Mental Health to Tanya K. Murphy (Grant K23 MH01739) and Wayne K. Goodman (Grant R01 MH45802). We thank Audrey Baumeister, Paula Edge, Natalie Johns, Erin Killiany, Jane Mutch, and Ohel Soto for their contributions to this study.
Received Date: August 19, 2004; Revised Date: March 29, 2005; Accepted Date: June 17, 2005
Abstract
To investigate the reliability and validity of the Yale Global Tic Severity Scale (YGTSS), 28 youth aged 6 to 17 years with Tourette's syndrome (TS) participated in the study. Data included clinician reports of tics and obsessive-compulsive disorder (OCD) severity, parent reports of tics, internalizing and externalizing problems, and child reports of depression and anxiety. All children participated in a 2nd YGTSS administration by the same rater 48 days later. Good internal consistency and stability were found for the YGTSS scores. YGTSS scores demonstrated strong correlations with parent-rated tic severity (r = .58–.68). YGTSS scores were not significantly related to measures of clinician ratings of OCD severity (r = .01–.15), parent ratings of externalizing and internalizing behavior (r = -.07–.20), and child ratings of depression (r = .02–.26) and anxiety (r = -.06–.28). Findings suggest that the YGTSS is a reliable and valid instrument for the assessment of pediatric TS.
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Gilles de la Tourette syndrome, or Tourette's syndrome (TS), is characterized by involuntary motor and vocal tics that last over 1 year and begin in childhood or early adolescence (American Psychiatric Association, 2000; Leckman & Cohen, 1999; World Health Organization, 2000). Motor tics are repetitive, automatic, and rapid movements of a complex or simple nature that affect multiple muscle groups. Vocal tics are varied and include sniffing, throat clearing, grunting, and repeating words or phrases. Childhood TS runs a waxing and waning course and is often comorbid with other psychiatric conditions, including attention-deficit/hyperactivity disorder (ADHD; Comings, 1994; Robertson, Banerjee, Eapen, & Fox-Hiley, 2002; Sukhodolsky et al., 2003), obsessive-compulsive disorder (OCD; Hebebrand et al., 1997; Pauls, Towbin, Leckman, Zahner, & Cohen, 1986; Robertson, 2003), disruptive behavior (Budman, Bruun, Park, Lesser, & Olson, 2000; Riddle, Hardin, Ort, Leckman, & Cohen, 1988; Sukhodolsky et al., 2003), and depressive and anxiety disorders (Carter et al., 2000; Coffey, Biederman, Smoller, et al., 2000; Coffey & Park, 1997; Robertson et al., 2002).
Although clinicians and researchers have uniformly recognized the importance of assessing tic severity among youth, it has been measured differently across instruments. The Tourette Syndrome Severity Scale (TSSS; Shapiro & Shapiro, 1984) contains five ordinal scales with differing ranges and item weights that focus on TS-related social impairment. The Tourette Syndrome Global Scale (TSGS; Harcherik, Leckman, Detlor, & Cohen, 1984) assesses the frequency and disruption of simple and complex tics, as well as common comorbid problems (e.g., behavioral problems, functional impairment). Finally, short, structured videotape protocols have been used to count tics (Shapiro & Shapiro, 1984; Tanner, Goetz, & Klawans, 1982). Although these instruments represent important advancements in pediatric TS assessment, numerous concerns about their use have been raised, including issues with scoring structures, practicality and efficiency, and limited psychometric support (Leckman et al., 1989).
To address these limitations, Leckman and colleagues (1989) developed the Yale Global Tic Severity Scale (YGTSS). The YGTSS is a semistructured clinician-rated instrument that assesses the nature of motor and phonic tics over the previous week. The clinician initially notes the presence of motor and phonic tics based on child and parent(s) reports and behavioral observations. Following this, the clinician rates the severity of motor and phonic tics on five separate dimensions each: number, frequency, intensity, complexity, and interference. The YGTSS also includes a separate impairment rating focusing on distress and impairment experienced in interpersonal, academic, and occupational realms. Five index scores are obtained: Total Motor Tic Score, Total Phonic Tic Score, Total Tic Score, Overall Impairment Rating, and Global Severity Score. The Total Motor Tic Score is derived by adding the five items pertaining to motor tics (range = 0–25); the Total Phonic Tic Score is derived by adding the five items pertaining to phonic tics (range = 0–25); the Total Tic Score is derived by adding the Total Motor Tic Score and the Total Phonic Tic Score; and the Overall Impairment Rating is rated on a 50-point scale anchored by 0 (no impairment) and 50 (severe impairment). A Global Severity Score is derived by summing the Total Motor Tic Score, Total Phonic Tic Score, and Overall Impairment Rating (range = 0–100).
Despite being widely used, only one psychometric investigation has been published on the YGTSS (Leckman et al., 1989). This sample included 105 children and adults (age range = 5–51 years) with a tic disorder. Good interrater agreement among three raters was found for the YGTSS scores in a sample of 20 children and adolescents with TS (with intraclass correlation coefficients [ICCs] for index scores ranging from .62 to .85). Walkup, Rosenberg, Brown, and Singer (1992) corroborated this finding in a second sample of 20 children and adolescents (the average Spearman rank coefficient among three raters for YGTSS Global Severity Score was .93). Convergent validity was supported as YGTSS scores were strongly related to corresponding TSGS scores (Pearson product-moment correlations ranged from .86 to .90). In addition, YGTSS scores were moderately to strongly related to clinician ratings of TS impairment (Pearson correlations ranged from .65 to .82) and moderately to strongly related to the TSSS (Pearson correlations ranged from .54 to .76). Discriminant validity was demonstrated by weak to moderate relations with clinician ratings of impairment due to ADHD (Pearson correlations ranged from -.03 to .18) and OCD (Pearson correlations ranged from .30 to .39). Finally, studies have demonstrated that the YGTSS is sensitive to treatment effects (Gaffney et al., 2002; Gilbert, Batterson, Sethuraman, & Sallee, 2004; Gilbert et al., 2003; Gilbert, Sethuraman, Sine, Peters, & Sallee, 2000; Mueller-Vahl et al., 2003; Scahill, Leckman, Schultz, Katsovich, & Peterson, 2003).
Although encouraging, the following important psychometric questions have not been examined: What is the stability and internal consistency of YGTSS scores, and how does the YGTSS relate to parent-rated TS symptoms and measures of anxiety and depression? That the stability has not been reported is notable in light of recent data suggesting that scores on the second administration of clinician-rated instruments are often lower than on the first administration (Arrindell, 2001; Jensen, Roper, Fisher, & Piacentini, 1995). The implications of this finding are significant and may suggest that observed treatment effects are actually due to the retest effect rather than the impact of the treatment. Given this, it is important to document potential temporal fluctuations in YGTSS scores. In light of the high comorbidity with internalizing and externalizing disorders, along with the frequency with which child measures do not differentiate between disorders (Schniering, Hudson, & Rapee, 2000), it is also important to examine the extent to which the YGTSS taps unique constructs.
This research examined the psychometric properties of the YGTSS. The following questions were addressed: (a) What are the internal consistency and interscale correlations of the YGTSS? (b) What is the stability of the YGTSS over a period of approximately 7 weeks? And (c) does the YGTSS correlate strongly with a measure of TS symptomatology, and weakly with measures of externalizing behaviors, OCD, anxiety, and depressive symptomatology?
Method
Participants
A total of 28 (14 female and 14 male) children diagnosed with TS according to DSM-IV-TR (American Psychiatric Association, 2000) participated in this research. Participants were referred from area physicians and the University of Florida child psychiatry clinic. Diagnoses were derived from the Schedule for Affective Disorders and Schizophrenia for School-Age Children—Lifetime and Present versions (K-SADS-PL; Kaufman et al., 1997) and confirmed by Tanya K. Murphy, who was a board certified child psychiatrist with 10 years of experience. The sample was composed primarily of White participants (94.5%), followed by Latino American (4.5%). At the initial assessment, the children ranged in age from 6 to 17 years with a mean age of 10.47 years (SD = 2.51 years). Participants generally came from middle to higher socioeconomic status families (mean income = $116,607), although there was fair variation (SD = $81,996, range = $20,000–$340,000). All of these children were being treated pharmacologically at study onset with the most common medications including selective serotonin reuptake inhibitors, clonidine, guanfacine neuroleptics, and stimulants. Secondary diagnoses, when present, included ADHD (n = 6), OCD (n = 14), major depression (n = 2), generalized anxiety disorder (GAD; n = 1), oppositional defiant disorder (ODD; n = 3), and social phobia (n = 1). Tertiary diagnoses, when present, included ADHD (n = 4), GAD (n = 3), ODD (n = 1), and conduct disorder (n = 1).
Measures
YGTSS
The characteristics and psychometric properties of this measure were previously discussed.
Children's Yale-Brown Obsessive Compulsive Scale (CY-BOCS; Scahill et al., 1997)
The CY-BOCS is a 10-item semistructured clinician-administered measure of obsession and compulsion severity. Items are rated over the previous week on a 5-point Likert-type scale ranging from 0 to 4, with higher scores corresponding to greater symptom severity. Items about obsessions and compulsions are summed to derive the Obsession and Compulsion Severity Scales, respectively. The Obsession and Compulsion Severity Scales are summed to derive the Total Severity Score. Only the Total Severity Score was used in this study. The CY-BOCS has exhibited good internal consistency ([alpha] = .90), test-retest reliability over 6 weeks (Total Score ICC = .79), and convergent and discriminant validity (Scahill et al., 1997; Storch et al., 2004b). Cronbach's alpha for the Total Severity Score in this sample was .94.
Tourette's Disorder Scale—Parent Rated (TODS-PR; Shytle et al., 2003)
The TODS-PR is a 15-item parent-rated scale designed to measure a broad range of symptoms common to Tourette's disorder including tics, obsessions, compulsions, inattention, hyperactivity, aggression, and mood disturbances. The TODS-PR has four factorially derived subscales: Aggression, ADHD, Obsessive-Compulsive Disorder/Anxiety, and Tics. Internal consistency of the TODS-PR Total Score and factors has been found to be adequate: TODS-PR Total Score (15 items; .91), Tics factor (2 items; .64), Aggression factor (5 items; .91), ADHD factor (4 items; .91), and OCD/Anxiety factor (4 items; .81). In addition, the TODS-PR has demonstrated good convergent and discriminant validity (Shytle et al., 2003; Storch et al., 2004a). Cronbach's alpha in this sample for the Tics, Aggression, ADHD, and OCD factors were .69, .90, .92, and .74, respectively.
Children's Depression Inventory (CDI; Kovacs, 1981)
The CDI is a widely used 27-item self-report measure that yields a severity rating of depressive symptomatology across affective, cognitive, somatic, and behavioral domains. On each item, the child is instructed to choose one of three statements that best describes his or her feelings over the past 2 weeks. Good psychometric properties have been reported including adequate internal consistency and test-retest reliability (Smucker, Craighead, Craighead, & Green, 1986) and construct validity (Kovacs, 1992; Saylor, Finch, Spirito, & Bennett, 1984). Cronbach's alpha in this sample was .86.
The Multidimensional Anxiety Scale for Children (MASC; March, Parker, Sullivan, Stallings, & Conners, 1997)
The MASC is a 39-item self-report questionnaire that assesses symptoms of general, social, and separation anxiety in children and adolescents. Items are rated on a 4-point Likert-type scale (0 = never true about me, 1 = rarely true about me, 2 = sometimes true about me, 3 = often true about me), and a total score is computed by summing all items. The MASC has good internal consistency ([alpha] = .90) and test-retest reliability over intervals of 3 weeks and 3 months (r = .88 and .87; March et al., 1997; March, Sullivan, & Parker, 1999). The convergent and discriminant validity of the measure was supported, as the MASC correlated moderately with the Revised Children's Manifest Anxiety Scale (Reynolds & Richmond, 2000) (r = .63) and was not significantly correlated with the CDI (Kovacs, 1992) (r = .19) or the Abbreviated Symptom Questionnaire (Goyette, Conners, & Ulrich, 1978) (r = .07). Cronbach's alpha in this sample was .90.
Procedure
Following permission from the University of Florida institutional review board, parental consent and child assent were obtained. After this, children and their parent(s) were taken to a private, secure office and administered the K-SADS-PL to establish DSM-IV diagnoses. A board-certified child psychiatrist (Tanya K. Murphy) confirmed diagnoses based on all available clinical information. Following administration of the K-SADS-PL, a different clinician administered the YGTSS and CY-BOCS to the parent(s) and child jointly. Procedures for the YGTSS interviewer training were described in Leckman et al. (1989); procedures for CY-BOCS training were described in Scahill et al. (1997). Clinicians were three licensed psychiatrists and one psychiatric nurse with extensive clinical experience working with pediatric TS. Training consisted of an instructional meeting about the YGTSS content and structure with Tanya K. Murphy.
Following administration of the structured interviews, children completed the MASC and CDI, and parents completed the TODS-PR. All measures were completed in a private room. To examine the stability of the YGTSS over 47.8 days (SD = 21.4; range = 27 to 104 days), a different clinician readministered the YGTSS using identical procedures. This time distribution was primarily due to scheduling difficulties.
Data Analysis
Cronbach's alpha (Cronbach, 1951) was computed to assess the internal consistency of the YGTSS scores at both the first and second administration. To assess test-retest reliability across the first and second YGTSS administrations, one-way random effects ICCs (Shrout & Fleiss, 1979) were used to allow for intersubject variability. ICC is a measure of agreement for dimensional measurements. Scores range between 0 and 1, with scores greater than .75 indicating excellent reliability (Nunnally & Bernstein, 1994). Pearson product-moment correlations were computed to examine the relationships among YGTSS scores and measures of TS symptomatology, externalizing behaviors, OCD, anxiety, and depressive symptomatology.
Results
Internal Consistency
Cronbach's alpha reliability coefficients were high for the Total Motor Tic Score ([alpha] = .92 and .92), Total Phonic Tic Score ([alpha] = .93 and .93), and Total Tic Score ([alpha] = .93 and .94) at first and second administrations.
Interscale Correlations
At the first assessment, the Total Motor Tic Score was moderately correlated with the Total Phonic Tic Score and YGTSS Overall Impairment Rating. The first administration Total Phonic Tic Score and YGTSS Overall Impairment Rating were strongly correlated (see Table 1). Similar results were found among second administration scores.

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Table 1 Descriptive Statistics and Intercorrelations Between the YGTSS Scores and Various Measures of Psychological Functioning
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Stability
The stability of the YGTSS scores over 47.8 days (SD = 21.4) were examined using one-way random effects ICCs. ICCs ranged from fair to excellent for the Total Motor Tic Score (ICC = .77; 95% confidence interval [CI] = .49 to .89), Total Phonic Tic Score (ICC = .90; 95% CI = .78 to .95), Total Tic Score (ICC = .88; 95% CI = .73 to .94), Overall Impairment Rating (ICC = .88; 95% CI = .74 to .95), and Global Severity Score (ICC = .89; 95% CI = .75 to .95). ICCs were also computed separately for participants (n = 19) whose readministration interval was below 47.8 days. For this subsample, stability ranged from fair to excellent for the Total Motor Tic Score (ICC = .85; 95% CI = .62 to .94), Total Phonic Tic Score (ICC = .93; 95% CI = .83 to .97), Total Tic Score (ICC = .92; 95% CI = .78 to .96), Overall Impairment Rating (ICC = .88; 95% CI = .71 to .95), and Global Severity Score (ICC = .91; 95% CI = .78 to .96). Stability was not calculated for participants whose administration interval was above 47.8 days because of the small number of such participants (n = 9).
Convergent and Discriminant Validity
Table 1 presents Pearson product-moment correlations for children with TS between the YGTSS scores and measures of parent-rated tics, internalizing and externalizing symptoms, clinician-rated OCD, and child-rated depression and anxiety. Correlations were strong between all of the YGTSS scores and the TODS-PR Tic factor. Discriminant validity was demonstrated with weak, nonsignificant correlations between the YGTSS scores and CY-BOCS Total, TODS-PR Aggression, ADHD, and OCD scores, CDI Total, and MASC Total.
Discussion
This study examined the psychometric qualities of the YGTSS in children and adolescents with TS. Unlike other instruments that measure pediatric TS, the YGTSS contains separate scales to assess motor and phonic tics, as well as tic-related impairment. Within clinical trials, the YGTSS represents the “reference standard” in pediatric tic assessment. However, limited psychometric data have been reported, particularly regarding the stability of scores, internal consistency, and convergent and discriminant validity.
Overall, the results of the present study support both the reliability and the validity of the YGTSS. The internal consistency of the Total Motor Tic Score, Total Phonic Tic Score, and Total Tic Score were high at both the first and second administrations. The moderate level of intercorrelation between the Total Motor and Phonic Tic Scores suggests that each measures relatively distinct but related dimensions of TS. Of interest, the Total Phonic Tic Score was more strongly related to the impairment index than the Total Motor Tic Score. There are several interpretations of this finding. First, phonic tics are generally understood to be more impairing than motor tics alone by virtue of simultaneous motor and phonic tics. Second, motor tics may be more easily hidden than phonic tics. Attention or disruption resulting from phonic tics may invite peer ridicule and/or reprimands should someone not understand the nature of TS.
A primary goal of this study was to report data on the stability of YGTSS scores. Others have cited the retest effect to be a source of unreliability in symptom measurement that may have significant implications for measuring treatment effects (Arrindell, 2001; Jensen et al., 1995; Storch, Masia-Warner, Dent, Roberti, & Fisher, 2004). Our findings suggest that the retest effect was not substantial in YGTSS scores for this sample, as scores were relatively consistent across administrations even with children being maintained on their prestudy pharmacological regimen. It is worth noting that the use of different raters at each time point provides for a more stringent test of stability and helps to control for rater bias.
The convergent validity of the YGTSS scores was supported by strong correlations with parent reports of tics. Although the high relationships suggest that parent ratings of tics may be an easier manner of collecting information, the YGTSS holds numerous advantages over parent reports. For example, YGTSS scores are based on all available information (e.g., parent and child reports, behavioral observations) as opposed to parent ratings in isolation. In addition, the YGTSS provides a qualitatively rich account of the type and nature of symptoms. The pattern of weak relations with measures of externalizing behaviors, OCD, anxiety, and depression provides strong discriminant validity support. The demonstrated divergence with these measures is noteworthy given the high comorbidity with externalizing symptoms (Budman et al., 2000; Comings, 1994; Riddle et al., 1988; Robertson et al., 2002; Sukhodolsky et al., 2003), internalizing symptoms (Carter et al., 2000; Coffey, Biederman, Geller, et al., 2000; Coffey, Biederman, Smoller, et al., 2000; Coffey & Park, 1997; Robertson et al., 2002), and OCD (Hebebrand et al., 1997; Pauls et al., 1986; Robertson, 2003).
Several limitations of this study should be noted. First, our sample was small and consisted of primarily Caucasian children. Further, complete demographic information was not available for this sample. It is not clear whether our findings can be generalized to other populations with differing demographic characteristics. The small sample also prevents us from analyzing the YGTSS dimensional structure. Indeed, the high relationship of the Total Phonic Tic Score to the Total Tic score (.92), Overall Impairment Rating (.91), and Global Severity Rating (.95) may suggest that a different dimensional structure may best explain the YGTSS. Given that interscale correlations are as high as their reliabilities, it is possible that all ratings are measuring the same construct and that a single-factor may underlie the YGTSS latent structure. Second, the 47.8-day interval used to estimate the YGTSS's stability was relatively short; future research should examine stability using a longer interval, particularly because slightly higher ICCs for a subsample whose readministration interval was below the mean may suggest lower stability over longer intervals. Third, we did not investigate differences in YGTSS scores across various diagnostic groups. It is uncertain the extent to which YGTSS scores would differentiate between children with other conditions, particularly given the high comorbidity between TS and other disorders. Thus, it will be important to examine the ability of the YGTSS to discriminate between children with TS and other internalizing and externalizing disorders. Fourth, some participants were receiving pharmacological services prior to study onset. Although no reported changes in pharmacological management occurred during the readministration interval, prior clinical services, changes in the effectiveness of medications, or the episodic nature of TS (Coffey, Biederman, Geller, et al., 2000) might have impacted the strength of the stability coefficients found. Finally, we do not have information on the interrater reliability of the study interviewers. On balance, one indication that rater agreement may be adequate is the strong ICC values over time even with the use of different raters. In other words, consistency is shown between two YGTSS administrations separated by time and completed by different interviewers.
Within these positive findings, further study and refinement of the YGTSS scoring structure may be necessary. For example, the distinction between motor and phonic tic has good face validity, but it is uncertain whether this scoring framework actually reflects the true latent structure. Using exploratory factor analysis, Leckman et al. (1989) found a two-factor model of motor and phonic tics that accounted for only 8% of the variance. Further study with factor analysis will provide information regarding the format and scoring structure of the YGTSS.
References
American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., text rev.). Washington, DC: Author. [Context Link]
Arrindell, W. A. (2001). Changes in waiting-list patients over time: Data on some commonly used measures. Beware! Behaviour Research and Therapy, 39, 1127–1247. [Context Link]
Budman, C. L., Bruun, R. D., Park, K. S., Lesser, M., & Olson, M. (2000). Explosive outbursts in children with Tourette's disorder. Journal of the American Academy of Child and Adolescent Psychiatry, 39, 1270–1276. [Context Link]
Carter, A. S., O'Donnell, D. A., Schultz, R. T., Scahill, L., Leckman, J. F., & Pauls, D. L. (2000). Social and emotional adjustment in children affected with Gilles de la Tourette's Syndrome: Associations with ADHD and family functioning. Journal of Child Psychology and Psychiatry, 41, 215–223. [Context Link]
Coffey, B. J., Biederman, J., Geller, D. A., Spencer, T., Park, K. S., Shapiro, S. J., & Garfield, S. B. (2000). The course of Tourette's disorder: A literature review. Harvard Review of Psychiatry, 8, 192–198. [Context Link]
Coffey, B. J., Biederman, J., Smoller, J. W., Geller, D. A., Sarin, P., Schwartz, S., & Kim, G. S. (2000). Anxiety disorders and tic severity in juveniles with Tourette's disorder. Journal of the American Academy of Child and Adolescent Psychiatry, 39, 562–568. [Context Link]
Coffey, B. J., & Park, K. S. (1997). Behavioral and emotional aspects of Tourette syndrome. Neurology Clinics, 15, 277–289. [Context Link]
Comings, D. E. (1994). Tourette syndrome: A hereditary neuropsychiatric spectrum disorder. Annals of Clinical Psychiatry, 6, 235–247. [Context Link]
Cronbach, L. (1951). Coefficient alpha and the internal consistency of tests. Psychometrika, 16, 297–334. [Context Link]
Gaffney, G. R., Perry, P. J., Lund, B. C., Bever-Stille, K. A., Arndt, S., & Kuperman, S. (2002). Risperidone versus clonidine in the treatment of children and adolescents with Tourette's syndrome. Journal of the American Academy of Child and Adolescent Psychiatry, 41, 330–336. [Context Link]
Gilbert, D. L., Batterson, R. J., Sethuraman, G., & Sallee, F. R. (2004). Tic reduction with risperidone versus pimozide in a randomized, double-blind crossover trial. Journal of the American Academy of Child and Adolescent Psychiatry, 43, 206–214. [Context Link]
Gilbert, D. L., Dure, L., Sethuraman, G., Raab, D., Lane, J., & Sallee, F. R. (2003). Tic reduction with pergolide in a randomized controlled trial in children. Neurology, 60, 606–611. Buy Now Bibliographic Links [Context Link]
Gilbert, D. L., Sethuraman, G., Sine, L., Peters, S., & Sallee, F. R. (2000). Tourette's syndrome improvement with pergolide in a randomized, double-blind crossover trial. Neurology, 54, 1310–1315. Buy Now Bibliographic Links [Context Link]
Harcherik, D. F., Leckman, J. F., Detlor, J., & Cohen, D. J. (1984). A new instrument for clinical studies of Tourette's syndrome. Journal of the American Academy of Child Psychiatry, 23, 153–160. [Context Link]
Hebebrand, J., Klug, B., Fimmers, R., Seuchter, S. A., Wettke-Schaefer, R., & Deget, F. et al. (1997). Rates for tic disorders and obsessive compulsive symptomatology in families of children and adolescents with Gilles de la Tourette syndrome. Journal of Psychiatric Research, 31, 519–530. [Context Link]
Jensen, P., Roper, M., Fisher, P., & Piacentini, J. (1995). Test-retest reliability of the Diagnostic Interview Schedule for Children (DISC 2.1): Parent, child, and combined algorithms. Archives of General Psychiatry, 52, 61–71. Bibliographic Links [Context Link]
Kaufman, J., Birmaher, B., Brent, D., Rao, U., Flynn, C., & Moreci, P. et al. (1997). Schedule for Affective Disorders and Schizophrenia for School-Age Children—Present and Lifetime version (K-SADS-PL): Initial reliability and validity data. Journal of the American Academy of Child and Adolescent Psychiatry, 36, 980–988. [Context Link]
Kovacs, M. (1981). Rating scales to assess depression in school-aged children. Acta Paedopsychiatria, 46, 305–315. [Context Link]
Kovacs, M. (1992). The Children's Depression Inventory [Manual]. Toronto, Ontario, Canada: Multi-Health Systems. [Context Link]
Leckman, J. F., & Cohen, D. J. (1999). Tourette's syndrome—Tics, obsessions, compulsions: Developmental psychopathology and clinical care. New York: Wiley. [Context Link]
Leckman, J. F., Riddle, M. A., Hardin, M. T., Ort, S. I., Swartz, K. L., Stevenson, J., & Cohen, D. J. (1989). The Yale Global Tic Severity Scale: Initial testing of a clinician-rated scale of tic severity. Journal of the American Academy of Child and Adolescent Psychiatry, 28, 566–573. [Context Link]
March, J. S., Parker, J. D., Sullivan, K., Stallings, P., & Conners, C. K. (1997). The Multidimensional Anxiety Scale for Children (MASC): Factor structure, reliability, and validity. Journal of the American Academy of Child and Adolescent Psychiatry, 36, 554–565. [Context Link]
March, J. S., Sullivan, K., & Parker, J. D. (1999). Test-retest reliability of the Multidimensional Anxiety Scale for Children. Journal of Anxiety Disorders, 13, 349–358. Bibliographic Links [Context Link]
Mueller-Vahl, K. R., Schneider, U., Prevedel, H., Theloe, K., Kolbe, H., Daldrup, T., & Emrich, H. M. (2003). Delta 9-tetrahydrocannabinol (THC) is effective in the treatment of tics in Tourette syndrome: A 6-week randomized trial. Journal of Clinical Psychiatry, 64, 459–465. [Context Link]
Nunnally, J., & Bernstein, I. H. (1994). Psychometric theory (3rd ed.). New York: McGraw-Hill. [Context Link]
Pauls, D. L., Towbin, K. E., Leckman, J. F., Zahner, G. E., & Cohen, D. J. (1986). Gilles de la Tourette's syndrome and obsessive-compulsive disorder. Evidence supporting a genetic relationship. Archives of General Psychiatry, 43, 1180–1182. [Context Link]
Reynolds, C. R., & Richmond, B. O. (2000). Revised Children's Manifest Anxiety Scale (RCMAS) manual. Los Angeles: Western Psychological Services. [Context Link]
Riddle, M. A., Hardin, M. T., Ort, S. I., Leckman, J. F., & Cohen, D. J. (1988). Behavioral symptoms in Tourette's syndrome. In D. J. Cohen, R. D. Bruun, & J. F. Leckman (Eds.), Tourette's syndrome and tic disorders: Clinical understanding and treatment (pp. 151–162). New York: Wiley. [Context Link]
Robertson, M. M. (2003). Diagnosing Tourette syndrome: Is it a common disorder? Journal of Psychosomatic Research, 55, 3–6. Bibliographic Links [Context Link]
Robertson, M. M., Banerjee, S., Eapen, V., & Fox-Hiley, P. (2002). Obsessive compulsive behaviour and depressive symptoms in young people with Tourette syndrome: A controlled study. European Child and Adolescent Psychiatry, 11, 261–265. [Context Link]
Saylor, C. F., Finch, A. J., Spirito, A., & Bennett, B. (1984). The Children's Depression Inventory: A systematic evaluation of psychometric properties. Journal of Consulting and Clinical Psychology, 52, 955–967. [Context Link]
Scahill, L., Leckman, J. F., Schultz, R. T., Katsovich, L., & Peterson, B. S. (2003). A placebo-controlled trial of risperidone in Tourette syndrome. Neurology, 60, 1130–1135. Buy Now Bibliographic Links [Context Link]
Scahill, L., Riddle, M. A., McSwiggin-Hardin, M., Ort, S. I., King, R. A., & Goodman, W. K. et al. (1997). Children's Yale-Brown Obsessive Compulsive Scale: Reliability and validity. Journal of the American Academy of Child and Adolescent Psychiatry, 36, 844–852. [Context Link]
Schniering, C. A., Hudson, J. L., & Rapee, R. M. (2000). Issues in the diagnosis and assessment of anxiety disorders in children and adolescents. Clinical Psychology Review, 20, 453–478. Bibliographic Links [Context Link]
Shapiro, A. K., & Shapiro, E. (1984). Controlled study of pimozide versus placebo in Tourette syndrome. Journal of the American Academy of Child Psychiatry, 23, 161–173. [Context Link]
Shrout, P. E., & Fleiss, J. L. (1979). Intraclass correlations: Uses in assessing rater reliability. Psychological Bulletin, 86, 420–428. Ovid Full Text Bibliographic Links [Context Link]
Shytle, R. D., Silver, A. A., Sheehan, K. H., Wilkinson, B. J., Newman, M., Sanberg, P. R., & Sheehan, D. (2003). The Tourette's Disorder Scale (TODS): Development, reliability and validity. Assessment, 10, 273–287. [Context Link]
Smucker, M. R., Craighead, W. E., Craighead, L. W., & Green, B. J. (1986). Normative and reliability data for the Children's Depression Inventory. Journal of Abnormal Child Psychology, 14, 25–39. Bibliographic Links [Context Link]
Storch, E. A., Masia-Warner, C., Dent, H. C., Roberti, J. W., & Fisher, P. (2004). Psychometric evaluation of the Social Anxiety Scale for Adolescents and the Social Phobia and Anxiety Inventory for Children: Construct validity and normative data. Journal of Anxiety Disorders, 18, 665–679. Bibliographic Links [Context Link]
Storch, E. A., Murphy, T. K., Geffken, G. R., Soto, O., Sajid, M., & Allen, P. et al. (2004a). Further psychometric properties of the Tourette's Disorder Scale—Parent Rated Version (TODS-PR). Child Psychiatry and Human Development, 35, 107–120. [Context Link]
Storch, E. A., Murphy, T. K., Geffken, G. R., Soto, O., Sajid, M., & Allen, P. et al. (2004b). Psychometric evaluation of the Children's Yale-Brown Obsessive Compulsive Scale. Psychiatry Research, 129, 91–98. [Context Link]
Sukhodolsky, D. G., Scahill, L., Zhang, H., Peterson, B., Kind, R. A., & Lombroso, P. J. et al. (2003). Disruptive behavior in children with Tourette's syndrome: Association with ADHD comorbidity, tic severity, and functional impairment. Journal of the American Academy of Child and Adolescent Psychiatry, 42, 98–105. [Context Link]
Tanner, C. M., Goetz, C. G., & Klawans, H. L. (1982). Cholinergic mechanisms in Tourette syndrome. Neurology, 32, 1315–1317. Buy Now Bibliographic Links [Context Link]
Walkup, J., Rosenberg, L. A., Brown, J., & Singer, H. S. (1992). The validity of instruments measuring tic severity in Tourette's syndrome. Journal of the American Academy of Child and Adolescent Psychiatry, 31, 472–477. [Context Link]
World Health Organization (2000). International classification of diseases and health related problems (10th rev.). Geneva, Switzerland: World Health Organization. [Context Link]
Keywords: Tourette's syndrome; Yale Global Tic Severity Scale; clinician-rated; validity; reliability
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