Table 1.

Studies of Anxiety in Children and Adolescents with ASD with Focus on Prevalence

Author (year)	Na	Sample Characteristicsb	Anxiety measurec	Control group(s)d	Primary Findings
Bellini (2004)	41	AD(19), AS(16), PDD-NOS(6).Age range: 12-18 (M: 14); No MR; IQ: 99.94±18.81 [R]	P, S	None	Levels of anxiety [physical, social, separation/ panic, total] in ASD significantly higher than controls; parents reported significantly higher levels of anxiety and internalizing problems; 49% of sample obtained clinically elevated score for social anxiety (compared to 14% of general population).
Bradley et al. (2004)	12	AD. Age range: 12-20 (M: 16); FSIQ≤75 [M]	P	Age, gender, nonverbal IQ-matched(12)	42% (n = 5) of sample reached clinical significance for anxiety problems, compared to 0% of mentally retarded sample without autism.
de Bruin et al. (2006)	94	PDD-NOS. Age range: 6-12 [C]	Int	None	Anxiety disorders were second most prevalent comorbid condition in sample; 55.3% of sample had at least one anxiety disorder.
Evans et al. (2005)	25	ASD(unspecified). Age range: NA (M:9); Mean IQ: 59.6 [S]	P	Down Syndrome(43); age-matched TD(37); mental age-matched TD (45)	Compared to all three control groups, ASD sample had more specific fears (eg, phobias) and medical fears.
Gadow et al. (2005)	301	AD(103),AS(80), PDD-NOS (118). Age range: 6-12 (M: 8); clinic referrals [C]	P, O	Non-ASD referrals(181); regular ed (404); special ed (60)	25.2% and 19.5% of males and females, respectively, with ASD screened positive for generalized anxiety disorder.
Kim et al. (2000)	59	HFA(40),AS(19). Age range: 9-14 (M: 12) [C]	P	None	Rate of anxiety in ASD was significantly higher than in community sample; 13.6% had clinically significant generalized anxiety; 8.5% had separation anxiety.
Lecavalier (2006)	487	ASD. Age range: 3-12 (M: 9) [S]	P, O	None	22% and 11% of sample obtained parent- and teacher-ratings, respectively, above average on Insecure-Anxious subscale of Nisonger child behavior rating form.
Melfsen et al. (2006)	7	AS. Age range: 7-18 (M: 12) [C]	S	Clinical group, various diagnoses(341)	For the seven subjects in the clinical group with AS, mean social anxiety score was above clinical cutoff (M = 22.68).
Muris et al. (1998)	44	AD (15), PDD-NOS (29). Age range: 2-18 (M: 9) [C]	Int	None	37 (84%) met full criteria for at least one anxiety disorder. Simple phobia was most common disorder (n = 28).
Simonoff et al. (2008)	112	AD(62), PDD-NOS(50). Age range: 10-14 (M: 11) [R]	Int	None	41.9% met criteria for at least one anxiety disorder. Social anxiety disorder was the most common disorder (29.2%).
Sukhodolsky et al. (2008)	171	AD(151), AS(6), PDD-NOS(14). Age range: 5-14 (M:8) [C]	P	None	73 (43%) met screening cut-of criteria for at least one anxiety disorder. Higher levels of anxiety associated with higher IQ, functional language use, and stereotyped behaviors.

TD=typically developing

^aSize of ASD sample

^bDiagnosis: Number of participants with specific diagnoses. AD=Autistic Disorder, AS=Asperger’s Syndrome, HFA=High-Functioning Autism, PDD-NOS=Pervasive-Developmental Disorder-Not Otherwise Specified, ASD=sample not categorized by specific diagnoses

Source [] of ASD sample: [C] Clinical sample, [R] State/National resource center or registry, [M] Multiple sources (e.g., parent groups, local agencies), [S] School districts

^cAnxiety measure (modality): D=Direct: direct testing or assessment of child’s skills or knowledge; P=Parent: parent-report measure; O=Other: other-report (e.g., teacher); S=Self: self-rating; Obs=Coded behavioral observations; I=Interview of parent and/or child; C=Clinical observations only.

^dComposition of control group/comparison scores (N = number of subjects), if applicable. Note that only control groups ascertained as part of the study are included.