Abstract
It is unknown whether sex influences the diagnostic evaluation of autism spectrum disorder, or whether male and female adults within the spectrum have different symptom profiles. This study reports sex differences in clinical outcomes for 1244 adults (935 males and 309 females) referred for autism spectrum disorder assessment. Significantly, more males (72%) than females (66%) were diagnosed with an autism spectrum disorder of any subtype (x2 = 4.09; p = 0.04). In high-functioning autism spectrum disorder adults (IQ > 70; N = 827), there were no significant sex differences in severity of socio-communicative domain symptoms. Males had significantly more repetitive behaviours/restricted interests than females (p = 0.001, d = 0.3). A multivariate analysis of variance indicated a significant interaction between autism spectrum disorder subtype (full-autism spectrum disorder/partial-autism spectrum disorder) and sex: in full-autism spectrum disorder, males had more severe socio-communicative symptoms than females; for partial-autism spectrum disorder, the reverse was true. There were no sex differences in prevalence of co-morbid psychopathologies. Sex influenced diagnostic evaluation in a clinical sample of adults with suspected autism spectrum disorder. The sexes may present with different manifestations of the autism spectrum disorder phenotype and differences vary by diagnostic subtype. Understanding and awareness of adult female repetitive behaviours/restricted interests warrant attention and sex-specific diagnostic assessment tools may need to be considered.
Highlights
Autism spectrum disorder (ASD) is a neurodevelopmental condition diagnosed when there is evidence from early childhood of impairments in social functioning and communication co-occurring with repetitive behaviours and restricted interests (International Classification of Diseases– 10th Revision (ICD-10R); World Health Organization (WHO, 1993); Diagnostic and Statistical Manual of Mental Disorders, 5th ed. (DSM-5); American Psychiatric Association (APA), 2015)
This reduced impairment in females compared to males on the restricted interests/repetitive behaviours domain has been replicated in several previous studies with children and adolescents (Bölte et al, 2011; McLennan et al, 1993; Mandy et al, 2011; Park et al, 2012; Solomon et al, 2012; for a review, see Van Wijngaarden-Cremers et al, 2014) a recent study with boys and girls under the age of 5 years reported no significant differences in number of symptoms in this domain (Harrop et al, 2015)
There were no significant differences on any domains of the Autism Diagnostic Interview–Revised (ADI-R) or Autism Diagnostic Observation Schedule–Generic (ADOS-G) between males and females who were not diagnosed with ASD (N = 370, all ps > 0.3; Figure 1)
Summary
Autism spectrum disorder (ASD) is a neurodevelopmental condition diagnosed when there is evidence from early childhood of impairments in social functioning and communication co-occurring with repetitive behaviours and restricted interests (International Classification of Diseases– 10th Revision (ICD-10R); World Health Organization (WHO, 1993); Diagnostic and Statistical Manual of Mental Disorders, 5th ed. (DSM-5); American Psychiatric Association (APA), 2015). The third, including a sample of ASD individuals aged 6–36 years, found age-related differences: in early development, males had more severe social difficulties than females, but in adolescence and adulthood, females exhibited more severe social and communication difficulties than males (McLennan et al, 1993) These studies were important first steps in investigation of sex differences across the lifespan, but conclusions were inconsistent and may have been limited by small numbers (N < 42/group) and wide age ranges within the samples. One other study has investigated gender and diagnosis in adults: Lai et al (2011) investigated 62 adults (aged 18–45 years) with previous diagnoses of high-functioning autism or Asperger syndrome They reported that ASD females had fewer repetitive and stereotyped behaviours than males both in childhood (reported retrospectively) and currently. To compare characteristics (age, alternative mental health diagnoses) of males and females with suspected ASD, but who did not receive a diagnosis of an ASD
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