Conceptual issues
In 1944 Hans Asperger, an Austrian pediatrician,
writing in German, described four boys aged between
6 and 11 years who had come to his attention because
of difficulties relating to their peers ([3] translated in
[28]). Unknown to him, a child psychiatrist working
at Johns Hopkins in Baltimore, Leo Kanner, described
11 children with similar impairments of social inter-
action, communication and behavior the previous
year, and coined the term infantile autism’ [44].
Wing [103] essentially introduced Asperger’s syn-
drome to the English speaking scientific community
when she described 34 cases, aged between 5 and
35 years, who had a clinical presentation similar to
Asperger’s account. Wing, however, proposed some
modifications to the syndrome based on her cases.
For example, although Asperger thought the condi-
tion unrecognizable prior to 3 years of age, Wing
suggested that difficulties were present in the first
2 years of life, including the absence of imaginative
play and speech abnormalities. Wing also noted the
similarities between autism and Asperger syndrome
(AS). However, although most researchers have
drawn close parallels between AS and autism, arguing
for the existence of a continuum, the autism spectrum
disorders (ASDs) [104], the relationship between AS
and autism remains unresolved, as will be discussed
subsequently [45, 46, 61, 109].
Before its introduction in the ICD-10 [110] and
DSM-IV [1], AS tended to be conceptualized as either
Marc R. Woodbury-Smith
Fred R. Volkmar
Asperger syndrome
Accepted: 8 April 2008
Published online: 18 June 2008
j Abstract Asperger syndrome
(AS) is a chronic neurodevelop-
mental disorder of social interac-
tion, communication, and a
restricted range of behaviors or
interests. Although not generally
associated with intellectual dis-
ability, the severe social disability
and, in many cases, associated
mental health and other medical
problems, result in disability
throughout life. The diagnosis is
often delayed, sometimes into
adulthood, which is unfortunate
because there are now a range of
interventions available, and the
current evidence supports inter-
vention starting as early in child-
hood as possible. The aim of this
review is to present a description
of AS, an up to date synopsis of
the literature pertaining to its
etiology, co-morbidity and inter-
vention options, and a discussion
of current nosological controver-
sies.
j Key words Asperger syn-
drome – autism spectrum disor-
ders
REVIEW
Eur Child Adolesc Psychiatry (2009)
18:2–11 DOI 10.1007/s00787-008-0701-0
E
C
A
P
7
0
1
M.R. Woodbury-Smith (&)
Autism Research Centre and Section of
Developmental Psychiatry
University of Cambridge
Douglas House, 18 b Trumpington Road
Cambridge CB2 2AH, UK
E-Mail: marcwoodburysmith@doctors.
org.uk
F.R. Volkmar
Yale Child Study Center
Yale University School of Medicine
230 South Frontage Road
New Haven 06520, USA

(1) a mild form of autism, (2) a manifestation of aut-
ism in people of normal intellectual ability, (3) a
higher verbally functioning form of autism, or (4) a
socially motivated’ form of autism. To complicate
things, several different diagnostic criteria had been
proposed. Its inclusion in ICD-10 and DSM-IV was
intended to provide a set of criteria to overcome this
problem. In the field trial conducted as part of DSM-IV
and ICD-10 cases with clinical diagnoses of Asperger
disorder were noted to differ BOTH from those with
autism (e.g., in terms of verbal-performance IQ profile
and increased rates of unusual circumscribed interests
in AS cases) and those with pervasive developmental
disorders not otherwise specified (PDD-NOS), with
significantly greater severity of social difficulties in
cases of AS [99]. Although offering the possibility of a
single set of criteria that allow data across studies to be
compared, the result has, unfortunately, been simply
to change rather than solve the conceptual problems.
When AS was introduced in the ICD-10 and DSM-
IV it was placed alongside autism as a pervasive
developmental disorder, sharing the same criteria
with autism, but differing in terms of its apparently
normal cognitive functioning and language develop-
ment, the onset’ rule, and on the basis of a number of
communicative impairments that are present in aut-
ism but absent from AS. In addition, autism auto-
matically takes priority in the diagnostic hierarchy
(the precedence’ rule). However, it has been argued
that because of these onset and precedence rules’,
diagnosing AS becomes a near impossibility [52, 58],
and the diagnosis is tilted’ towards autism on the
basis of vague developmental phenomena rather than
on real empirical data concerning developmental
pathways to social disability [109]. In addition, in
view of the fact that they share’ diagnostic criteria,
the study of the differentiation of AS vis-a
`
-vis autism
has become problematic and tautological, and,
therefore, it is no surprise that most research supports
a relationship between them, and examination of
external validity thus becomes meaningless.
It is important for the classification debate to move
beyond the current arguments concerning the rela-
tionship between autism and AS, and instead examine
the external validity of more sophisticated opera-
tionalised criteria. Several different models are pos-
sible, based on the absence or presence of early
language impairments, or based on active but odd’
versus socially aloof’ groupings for example. At the
current time, the strongest evidence for external
validity is when a definition closer to Asperger’s
description is used [46], as emphasized in the text
revision of the DSM-IV, but, sadly, not incorporated
into its diagnostic criteria.
Another related nosological uncertainty is the
internal validity of AS. As discussed subsequently,
both ICD-10 and DSM-IV have de-emphasized the
communication impairment in favor of the social and
behavioral features. This is unfortunate, as Asperger,
Wing and others have argued that they are common
and an essential feature. What is also unclear, how-
ever, is whether people with AS differ from one an-
other because of differences in severity of symptoms,
or whether there are subgroups’ according to differ-
ent phenotypic features, such as communication fea-
tures, or pattern of ritualistic behaviors [29, 73, 82,
86]. The results have failed to reach any consensus.
Whilst a number of studies have shown that people
with AS differ according to a severity gradient [73,
86], others have shown evidence for subtypes [29, 82],
which is also reflected in everyday clinical practice,
where wide variation in symptomatology is seen. It is
important to clarify this from both a nosological and
genetic point of view.
Clinical characteristics
Most experts agree that impairment of reciprocal
social interaction is the sine qua non of both AS and
autism [95]. People with AS are typically motivated to
interact with others, but find themselves socially iso-
lated because of their odd communication style [45,
95, 103], which is often overly formal and may take
the form of an in-depth monologue about a topic of
special interest regardless of whether their interlocu-
tor is interested or not. As Asperger originally
emphasized, these are children who talk before they
walk’ and words are their lifeline’—a stark contract
to autism where speech is typically delayed and usu-
ally not a source of great strength. In AS speech is
often verbose and tangential. There may also be
peculiarities to the speech itself [45, 95, 103]. For
example, it may lack the normal prosody and may
also be odd in terms of volume, rate or rhythm.
Sometimes pauses reflect the difficulties people with
AS have in formulating answers to questions and
structuring their discourse. As previously indicated,
these pragmatic language impairments were unfor-
tunately de-emphasized in the DSM-IV and ICD-10.
People with AS often engage in restricted and
repetitive patterns of behavior [45, 95, 103]. Whilst
these are categorized in both ICD-10 and DSM-IV as
being of four different types, they can be usefully
conceptualized as lower level’ (including stereotyped
motor movements) and higher level’ (including rit-
uals and circumscribed interests). Among people with
AS, these behaviors are more likely to manifest as
resistance to change in a personal routine or in their
immediate environment, or with the pursuit of a
circumscribed interest. Such interests are generally
focussed on amassing large amounts of information
M.R. Woodbury-Smith and F.R. Volkmar 3
Asperger syndrome