Self-Reports Vs Observer Ratings of Autistic Traits: A Comparison of Their Validity over the Adult Lifespan

Background: Autism Spectrum Disorder (ASD) is a lifelong condition, yet prevalence rates in adulthood are thought to be “underestimated, under-reported and underdiagnosed due to generational effects, evolving diagnostic criteria and developmental changes across the life course” (Wright et al., 2016). Recent research (Ashwood et al., 2016) has highlighted that self-report measures of autistic traits, which are often used as screening instruments for pre-diagnostic referrals (Sizoo et al., 2015), do not correlate with observer-rated measures (ADOS-2). This has important implications for the use of self-report measures as diagnostic screeners and raises questions about factors that might play a role in poor diagnostic validity of self-reports. Age and general intellectual functioning might play an important role in this context because greater life experience and ability to contemplate ones strengths and weaknesses may render self-reports more accurate. Mental health difficulties, such as anxiety and depression, and meta-cognitive difficulties such as those characterising Alexithymia, may also be involved since such co-morbidities may skew perceptions of personal strengths and weaknesses, whilst also moderating the expression of certain clinical features (e.g., repetitive behaviours).

Objectives: We examined the association between self-report (AQ) and observer-rated (ADOS) autistic traits and explored possible moderating effects of age, age of diagnosis, intellectual ability, co-morbid mental health difficulties and alexithymia.

Methods: 109 younger (<50yrs; n = 76) and older (>50yrs; n = 33) adults with a clinical diagnosis of ASD, recruited across three sites, completed the ADOS-2, the AQ and a measure of general intellectual functioning (WAIS or WASI). A sub-sample of 40 adults completed self-report measures of anxiety (BAI), depression (BDI) and alexithymia (TAS-20).

Results: Data from 109 participants confirmed previous reports of lack of association between self-reported autistic traits (AQ) and observer-based ratings (ADOS-2; r=.128, ns). Contrary to predictions, this was true for both younger and older adults, independent of age-of-diagnosis, and for individuals with above- and below-average IQs of 100. Interestingly, however, both age (r=.34) and IQ (r=.30) were positively correlated with AQ (p<.001) but not ADOS-2 scores, suggesting that older and more able autistic adults tend to report greater autism-related difficulties even when this is not necessarily borne out in their expressed behaviour. In the sub-sample of 40 adults, anxiety, depression and alexithymia could again not account for the absent correlation between AQ and ADOS-2 scores. However, whilst AQ scores were strongly correlated with BAI (r=.47), BDI (r=.60) and TAS-20 (r=.56) scores, none of these correlated with ADOS-2 (r<.12, ns).

Conclusions: The findings replicate previous observations of a lack of correlation between self-report and observer-rated measures of autistic traits in older and younger autistic adults of varying ability levels. The reliable correlations between the AQ (but not ADOS) and measures of anxiety, depression and alexithymia suggest that the AQ may be sensitive to non-specific mental-health vulnerabilities rather than to the defining characteristics of ASD specifically. These findings hold important implications for clinical practice concerning referral for diagnosis in adulthood and later life, and post-diagnostic support pathways that enable autistic individuals to achieve better quality of life.