While typical aging is associated with several functional changes, the developmental trajectory of individuals with autism
spectrum disorder (ASD) after young adulthood is not well charted (e.g., Happé & Charlton, 2012; Piven & Rabins, 2011).
The central aim of the current doctoral thesis was, therefore, to examine age-related differences across the adult lifespan
(up to 80 years) in three essential domains, either for ASD or typical aging: ASD symptomatology (Chapter 2), co-occurring
psychopathology (Chapter 3), and cognitive functioning (Chapters 4, 5, and 6). First, we found a peak in self-reported ASD
traits and sensory sensitivity in middle adulthood, which was not reported by close proxies. Second, middle adulthood was
also a vulnerable period for depression, but older adults with ASD less often met diagnostic criteria for psychiatric disorders
and specifically social phobia. Nevertheless, a large amount of individuals with ASD (79%) suffered from a psychiatric condition
at least once in their lives. Third, we demonstrated that age-related patterns are similar or reduced in ASD compared to a
typically developing control group, but not increased. Furthermore, most cognitive strengths and weaknesses occurring in adulthood
were still present in old age. Nevertheless, if cognitive weaknesses were present in ASD, these were subtle and not pronounced.
Despite these results, adults with ASD reported to experience many cognitive daily failures, showing an important discrepancy
that warrants further research. We discussed potential drawbacks and (clinical) implications of our findings.