Outcome in High-Functioning Adults with Autism with and Without Early Language Delays: Implications for the Differentiation Between Autism and Asperger Syndrome
Journal of Autism and Developmental Disorders
Outcome in High-Functioning Adults with Autism With and Without Early Language Delays: Implications for the Differentiation Between Autism and Asperger Syndrome
Patricia Howlin 0
0 Department of Psychology, St. George's Hospital Medical School , Cranmer Terrace, London SW17 ORE , U.K.
The question of whether Asperger syndrome and high-functioning autism should be considered as the same or different conditions has been a source of debate and controversy over recent years. In the present study, 34 adults with autism who had shown early delays in language were compared with 42 individuals who were reported to have had no such delays, either in their use of words or phrases. All participants were at least 18 years of age, had a nonverbal IQ of 70 or above and met ADI-R criteria for age of onset, communication and social impairments, and stereotyped behaviors. Those in the language delay group were diagnosed as having high-functioning autism. The remainder were designated as having Asperger syndrome. The groups were matched for age, nonverbal IQ and gender. No significant differences were found between the groups either in their total ADI-R algorithm scores, or in their algorithm scores on individual domains. Social outcome ratings and ADI-R scores based on current functioning also failed to differentiate between the groups. Scores on tests of language comprehension and expression were also similar, but in both groups language abilities were well below chronological age level. The implications of these results with respect to the differences between Asperger syndrome and high-functioning autism are discussed. The poor performance on language tests also challenges the assumption that early language development in Asperger syndrome is essentially normal.
High-functioning autism; Asperger syndrome; long-term outcome
INTRODUCTION
The issue of whether autism and Asperger
syndrome are different conditions (albeit part of the same
spectrum of disorders) has been a source of continuing
debate over recent years (cf. Klin, Volkmar, & Sparrow,
2000; Schopler, Mesibov, & Kunce, 1998). There is
also considerable disagreement about the validity of the
diagnostic criteria used in DSM-IV (APA, 1994) and
ICD-10 (WHO, 1992) to distinguish between the two
conditions, (Kim, Szatmari, Bryson, Streiner, & Wilson,
2000; Kugler, 1998; Leekam, Libby, Wing, Gould, &
Gillberg, 2000; Manjiviona & Prior, 1999). Indeed,
several studies now suggest that if strict DSM/ICD
criteria are applied, a diagnosis of Asperger syndrome
becomes unlikely, or even impossible (Eisenmajer et al.,
1996; Ghaziuddin, Tsai & Ghaziuddin, 1992; Manjiviona
& Prior, 1995; Mayes & Calhoun, 2001; Miller &
Ozonoff, 1997; Szatmari, Archer, Fisman, Streiner &
Wilson, 1995).
Wing, having been responsible for first bringing
Aspergers original writings to the attention of
clinicians in 1981, now expresses her concern that she may
have opened a Pandoras box (Wing, 2000). Her
original intention, to emphasize the fact that there was no
evidence for a distinction between Asperger syndrome
and autism, has frequently been overlooked. Instead,
her account led to widespread research into the
possible differences between the two conditions. Inadequate
group matchings, small samples, and, above all, lack of
agreement on diagnostic criteria have meant that few
of these studies have produced any conclusive results
(c.f. Klin et al., 2000). Despite this, the differential
diagnosis can have implications for services, with
individuals diagnosed as having Asperger syndrome or
Asperger disorder sometimes being deprived of the
level of support that is offered to those diagnosed as
having autism (Klin & Volkmar, 2000; Department of
Health, 2001).
Current Research Evidence
A systematic search of the literature over the past
15 years, using the major databases (MEDLINE,
PsychINFO, etc.) was conducted together with an additional
trawl of journals with a focus on developmental
disorders (Journal of the American Academy of Child and
Adolescent Psychiatry, Journal of Child Psychology
and Psychiatry, Journal of Autism and Developmental
Disorders, Autism, etc.), and recent collections of
chapters in edited volumes (Klin et al., 2000; Schopler et al.,
1998). Twenty-six separate studies were identified in
which a direct comparison between individuals with
high-functioning autism (HFA) (IQ 701) and Asperger
syndrome had been conducted and in which diagnostic
criteria and measures of IQ were adequately specified.
Tables I and II summarize these studies, indicating the
general areas investigated, the diagnostic systems used,
the number and ages of participants, and the general
conclusions of each.
Table I. Summary of Findings in Studies Comparing Individuals with Asperger Syndrome
and High-Functioning Autism Matched for Full-Scale IQ
General clinical characteristics
1. Szatmari et al., 1990 (Wings criteria) Age Mean (range) HFA 23, AS14 yr
2. Mayes (...truncated)